The design, construction and calibration of a small wind tunnel

Citation preview

THE DESIGN, CONSTRUCTION, AND CALIBRATION OF A mAUL WIND-TUNNEL

A T h e s is P re s e n te d to t h e F a c u l t y o f t h e G r a d u a te S c h o o l The U n i v e r s i t y o f S o u th e r n C a l i f o r n i a

In P a r t i a l F u lfillm e n t o f t h e R e q u ir e m e n ts f o r t h e D e g ree M a s te r o f S c ie n c e i n M e c h a n ic a l E n g in e e r in g

by Roy V a l e n t i n e Staiith F e b r u a r y 1950

UMI Number: EP60499

All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion.

Dissertation Publishing

UMI EP60499 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code

ProQuest ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 4 8 1 0 6 - 1346

Mec .

'5-0

5 i s t

This thesis, written by

/7 ; under the guidance of h.X.S~Faculty Committee, and approved by all its members, has been presented to and accepted by the Council on Graduate Study and Research in partial fulfill­ ment of the requirements for the degree of

________ Ma s t e r o f S e ie n o e i n _________ .............. M e c h a n ic a l En g i n e e r i n g ............... r>ate Jan u ary 10 , 1 950

Faculty Committee

nrman

JZct+r'm \j< . c , v

TABLE OF CONTENTS CHAPTER I .

PAGE

PRIMARY CONSIDERATIONS............................................................

1

The n e e d o f a w i n d - t u n n e l f o r p u r p o s e s o f

II.

III.

i n s t r u c t i o n ..............................................................................

1

M o n e ta ry c o n s i d e r a t i o n s ......................................................

2

C o m m ercial t e s t i n g ...............................................................

Z

D e f i n i t i o n s o f t e i m s a n d s y m b o l s ..............................

3

O r g a n i z a t i o n o f t h e r e m a in d e r o f t h e t h e s i s .

.

6

A BRIEF ON WIND-TUNNEL H ISTO R Y ........................................

8

W in d - tu n n e l c l a s s i f i c a t i o n s ............................................

9

B a la n c e s y s te m s ......................................

12

W in d - tu n n e l c o m p o n e n ts .....................................................

14

The s u b j e c t t u n n e l . . . . .

.......................................

15

DESIGN OF THE TUNNEL................................................................

19

S iz e a n d s p e c i f i c a t i o n s .....................................................

19

V e l o c i t y s p e c i f i c a t i o n s a n d p o w er re q u ire m e n ts

..........................................................

22

T o rq u e b a l a n c e d e s i g n ..........................................................

24

S p h e re d r a g b a l a n c e ...........................................

27

L i f t an d d r a g beam s o f t h e t u n n e l b a l a n c e

IV .

s y s t e m .......................................................................................

30

METHODS AND PROBLEMS OF CONSTRUCTION.........................

33

Wooden c o n s t r u c t i o n ...............................................................

33

The f a n s e c t i o n .........................................................................

34

iii CHAPTER

PAGE The m o to r a n d i t s

s u p p o rt.

. . . . . . . . . .

35

M o to r f a i r i n g , a f t e r - b o d y , a n d s t r a i g h t e n i n g v a n e s ............................................................................................ The f a n a n d i t s V.

s p i n n e r .................................

37 40

INSTRUMENTS.......................................................................................

42

S t a t i c - p l a t e m an o m ete r an d p r e s s u r e o p e n i n g s ............................ V a r i a b l e - s l o p e i n c l i n e d m a n o m e te r.............................

45

............................................

46

Flow d i r e c t i o n i n d i c a t o r t u b e .......................................

48

B o u n d a ry l a y e r t u b e s ..........................................................

50

T he d r a g s p h e r e s a n d t h e i r b a la n c e s y s te m .

. .

51

The t o r q u e m e a s u r in g d e v i c e ............................................

53

The m o d e l b a la n c e s y s t e m .................................................

54

I n s t r u m e n t c o n s t r u c t i o n d i f f i c u l t i e s ....................

57

TUNNEL TESTS AND CALIBRATION...........................................

59

I n i t i a l t e s t s ..............................................................................

59

V e l o c i t y t r a v e r s e s ..............................................................

63

The p i t o t - s t a t i c t u b e .

V I.

43

.

V e lo c ity t r a v e r s e and e n e rg y r a t i o c a l i b r a t i o n t e s t s ........................................... Flow d i r e c t i o n i n t h e t h r o a t

V II.

70 ....................

75

C r i t i c a l R e y n o ld s Number c a l i b r a t i o n ....................

76

SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS. . . . Summary.

........................

85 85

iv CHAPTER

PAGE C o n c l u s i o n s ...................................................................................

85

R e c o m m e n d a tio n s.........................................................................

86

BIBLIOGRAPHY.................................................................................................

88

APPENDIX A.

T e s t s a n d C a l i b r a t i o n D a t a . .............................

90

I n d e x t o A p p e n d ix A..............................................................................

91

D e t e r m in a t io n o f m o to r s p e e d .....................................................

92

B la d e a n g le a d j u s t m e n t s ....................................................................

92

D e t e r m in a t io n o f b l a d e a n g le a t 0 .7 5 R ..............................

94

D e riv a tio n o f th e p i t o t - s t a t i c v e l o c i t y e q u a tio n . .

96

P i t o t - s t a t i c tu b e v e l o c i t i e s a t t h e g e o m e tr ic c e n t e r o f t h e t h r o a t ....................................................................

100

Frahm T a c h o m e te r c a l i b r a t i o n .....................................................

100

C a lib r a tio n o f th e to rq u e s c a le by dead w e ig h ts .

. .

103

i n p u t h o r s e p o w e r ..............................................................................

107

P i t o t - s t a t i c v e l o c i t y t r a v e r s e s .................................................

112

D e te r m in a tio n o f t h e r a t i o o f f a n h o rs e p o w e r t o

V e lo c ity tr a v e r s e and e n e rg y r a t i o

c a lib ra tio n

t e s t s .......................................................................................................... P lo w d i r e c t i o n c a l i b r a t i o n t e s t s

125

............................................

158

C r i t i c a l R e y n o ld s Number c a l i b r a t i o n t e s t s ....................

169

APPENDIX B.

F i g u r e s and B i l l o f M a t e r i a l s .........................

179

F i g u r e s ...........................................................................................................

180

B i l l o f m a t e r i a l s ..................................................................................

222

F u n d s e x p e n d e d .......................................................................................

230

LIST OF TABLES TABLE I. II.

PAGE T o rq u e B a la n c e C a l i b r a t i o n ................................................ P i t o t - S t a t i c V e l o c i t y a t t h e G e o m e tric C e n te r o f t h e T h r o a t ..........................................................

III.

64

Pan H o rs e p o w e r, I n p u t H o rs e p o w e r, V e l o c i t y , an d H o rse p o w e r R a t i o ..........................................................

IV .

V. V I.

V II. V III.

66

C o m p ariso n o f M e a su re d M o to r O u tp u t w i t h M a n u f a c t u r e r ’ s D a t a ..........................................................

68

A v e ra g e T h r o a t V e l o c i t y .....................................................

71

V e l o c i t y C a l i b r a t i o n an d E n e rg y R a tio C a l i b r a t i o n ..............................................................................

73

Plow D i r e c t i o n C a l i b r a t i o n ................................................

77

S t r u t T a r e D rag ( C r i t i c a l R e y n o ld s Number T e s t s ) ....................................................

IX .

61

79

C r i t i c a l R e y n o ld s Num ber C a l i b r a t i o n ........................

82

X.

M o to r S p e e d C o r r e l a t i o n

(P an a s R e c e iv e d ) . . .

93

XE.

M o to r S peed C o r r e l a t i o n

(B la d e A n g le 1 4 ^ ) . .

X II.

(iO

.

P i t o t - S t a t i c Tube V e l o c i t i e s a t t h e G e o m e tric C e n te r o f t h e T h r o a t ..........................................................

X III.

T o rq u e B a la n c e C a l i b r a t i o n ..................................

105

XIV.

( T h is i s a c o n t i n u a t i o n o f T a b le X I I I ) ......

106

XV.

95

D e te r m in a tio n

X7I-XXE. XXU-XXXI.

o f t h e R a ti o H . P . y ^ / H . P . Tnp n t

V e l o c i t y T r a v e r s e s ...................... V e lo c ity

and E n e rg y R a ti o

101

•

1 1 4 -1 2 4

c a lib ra tio n .

1 2 7 -1 5 6

vi TABLE X X X II-X X X III.

XXXEV-XXXy.

PAGE C r i t i c a l R e y n o ld s N um ber, S t r u t T a r e D r a g .....................................................

1 7 1 -1 7 2

C r i t i c a l R e y n o ld s Number C a l i b r a t i o n .

1 7 3 -1 7 8

LIST OF CHARTS CHART I. II.

PAGE T o rq u e B a la n c e C a l i b r a t i o n C u rv e ................................. C urve o f P i t o t - S t a t i e V e l o c i t y a t t h e G e o m e tric C e n te r o f t h e T h r o a t ..................................

III.

V I.

67

C o m p ariso n o f M e a s u re d M o to r O u tp u t w i t h M a n u f a c t u r e r ’ s D a t a ..........................................................

V.

65

C u rv e s o f Fan H o rs e p o w e r, I n p u t H o rs e p o w e r, V e l o c i t y , an d H o rs e p o w e r R a t i o ..................................

IV .

62

A v e rag e T h r o a t V e l o c i t y .....................................

69 72

C a lib r a tio n C h a rt o f V e lo c ity v s S t a t i c - P l a t e D e f l e c t i o n , and E n e rg y R a tio v s S t a t i c - P l a t e D e f l e c t i o n ..................................................................................

V II.

C a l i b r a t i o n C h a r t o f Flow D i r e c t i o n v s S p e e d T a p .................................................................................................

V III.

74

78

C h a r t o f S t r u t T a re D rag v s S t a t i c - P l a t e D e f l e c t i o n ( C r i t i c a l R e y n o ld s Num ber T e s t s ) ............................................................................................

IX .

80

C a l i b r a t i o n C h a r t f o r C r i t i c a l R e y n o ld s N um ber............................................................................................

83

LIST OP FIGURES FIGURE 1.

PAGE

T h r e e - q u a r t e r View o f T u n n e l D u rin g M o to r In s ta lla tio n .

2.

.........................................................................

T h r e e - q u a r t e r View o f M o to r F a i r i n g , L o o k in g Down s t r e a m .......................................................................................

3.

180

181

T h r e e - q u a r t e r V iew o f M o to r F a i r i n g , L o o k in g U p s tr e a m ............................................................................................

182

4.

S id e View o f Fan and M o to r F a i r i n g ....................................

183

5.

S id e View Show ing M o to r C o n t r o l an d S t r a i g h t e n i n g V anes ...............................................................

6.

T h r e e - q u a r t e r View o f F a n , L o o k in g U p stre a m (F an i n M o t i o n ) .........................................................................

7.

184

185

T u r n in g V a n es a t E n tr a n c e t o t h e S e t t l i n g C h a m b e r ............................................................................................

186

8.

T o rq u e B a la n c e an d Fan G uard R i n g ...................................

187

9.

A d j u s t a b le I n c l i n e d M a n o m e t e r .............................................

188

10.

M a jo r A s se m b ly ..................................................................................

189

11.

P a n e l s an d P a n e l F r a m in g ............................................................

190

12.

P r im a r y Fram e and Fan M o u n t ..................................................

191

13.

Fan S e c t i o n ............................................

192

14.

F an G u ard and S h e e t M e ta l P a r t s ........................................

193

15.

T u n n e l T h r o a t M o d i f i c a t i o n .......................................................

194

16.

F an M ount F r a m e ...............................................................................

195

17.

M o to r M ount B e a r in g S u p p o r t s .................................................

196

ix FIGURE

PAGE

18.

M o to r M ount B e a r in g J o u r n a l s ...............................................

197

19.

Fan M ount A sse m b ly ........................................................................

198

20.

F an ( H a r t z e l l P r o p e l l e r Fan C o . ) ......................................

199

21.

Fan B la d e S e c t i o n s ........................................................................

200

22.

Fan Hub ( H a r t z e l l P r o p e l l e r Fan C o . ) .............................

201

23.

M o to r (K im ble E l e c t r i c C o. ) ......................

202

24.

M o to r D im e n s io n s (K im ble E l e c t r i c C o . ) .......................

203

25.

C o n t r o l l e r W irin g (C u tte r-H a m m e r I n c . ) .......................

204

26.

F a i r i n g and S p i n n e r ...................................................................

205

27.

T o rq u e-A rm P a r t s .

206

28.

I n s t r u m e n t s - P i t o t - S t a t i c Tube and B o u n d a ry

....................................................

L a y e r T u b e s .................................

207

29.

I n s t r u m e n t s - Flow D i r e c t i o n I n d i c a t o r .......................

208

30.

P a r t s - Flow D i r e c t i o n I n d i c a t o r ...........................

209

31.

P a r t s I I - Flow D i r e c t i o n I n d i c a t o r ............................

210

32.

I n s t r u m e n t S u p p o rt S y s t e m ....................................................

211

33.

P a r t s - I n s t r u m e n t S u p p o r t S y s t e m .................................

212

34.

S p h e re D rag B a la n c e S y s te m ....................................................

213

35.

D rag S p h e r e s an d S u p p o r t Arm................................................

214

36.

M odel

B a la n c e S y stem - P i c t o r i a l A ssem b ly . . . .

215

37.

M odel

B a la n c e S y stem - S u p p o r t F ra m e .............................

216

38.

M odel

B a la n c e S y stem - L i f t F r a m e ..................................

217

39.

M odel

B a la n c e S y stem - D rag Fram e an d

M i s c e ll a n e o u s P a r t s

...............................................................

218

X

FIGUBE

PAGE

40•

M odel B a la n c e S y ste m - L i f t an d D rag Beam s. . . .

219

41.

M odel S u p p o r t S y s te m .....................................................................

220

42.

P a r t s - M odel S u p p o rt S y s te m ..................................................

221

CHAPTER I PRIMARY CONSIDERATIONS I n t h e d e v e lo p m e n t o f t h e a p p a r a t u s d e s c r i b e d h e r e i n , t h e p rim e o b j e c t i v e w as t h e p r o d u c t i o n o f a w i n d - t u n n e l w h ic h w o u ld 1.

Be s u i t a b l e f o r u s e d u r i n g t h e i n s t r u c t i o n o f

u n d e r g r a d u a t e s t u d e n t s i n e le m e n t a r y a e ro d y n a m ic l a b o r a t o r y te c h n iq u e . 2.

C o st c o n s i d e r a b l y l e s s , i n a c t u a l c a s h o u t l a y ,

t h a n t h e p u r c h a s e p r i c e o f a t u n n e l o f c o m p a ra b le s i z e . 3.

N ot be u s e f u l f o r c o m m e rc ia l t e s t i n g a s a s o u r c e

o f d e s i g n i n f o r m a t i o n , a n d t h e r e f o r e , w o u ld b e a v a i l a b l e f o r s tu d e n t u se a t a l l tim e s . As a r e s u l t o f t h e s e c o n s i d e r a t i o n s m any o f t h e r e ­ f i n e m e n t s fo u n d i n m o d ern t u n n e l s w ere o m it t e d i n t h i s d e s ig n . I .

THE NEED OF A TOND-TUNNEL FOR PURPOSES OF INSTRUCTION

At t h e tim e t h i s p r o j e c t w as i n s t i g a t e d , t h e U n i­ v e r s i t y o f S o u th e r n C a l i f o r n i a h a d no o p e r a b l e w i n d - t u n n e l o n t h e L os A n g e le s cam p u s.

The U n i v e r s i t y h a d e s t a b l i s h e d

a c u r r i c u l a w h ic h o f f e r e d a n o p t i o n i n a e r o n a u t i c s u n d e r t h e D e p a rtm e n t o f M e c h a n ic a l E n g i n e e r i n g .

T h is o p t i o n

2 i n c l u d e d t h e c o u r s e "A ero d y n am ic L a b o r a to r y " f o r w h ic h e q u ip m e n t w as n e e d e d , a n d t h e t u n n e l h e r e i n d e s c r i b e d w as p r o p o s e d a s p a r t o f t h a t e q u ip m e n t. I n c o n n e c ti o n w i t h i n s t r u c t i o n , t h e p u r p o s e o f a w i n d - t u n n e l i s t o d e m o n s tr a te a e ro d y n a m ic phenom ena an d t h e r e b y s u b s t a n t i a t e , o r d i s p r o v e , a e ro d y n a m ic t h e o r i e s .

In

t h i s c a s e t h e r e w as n e e d o f t h e d e m o n s tr a ti o n o f e le m e n t a r y t h e o r y , an d o f f a m i l i a r i z a t i o n w i t h s im p le w i n d - t u n n e l t e c h ­ n iq u e .

The c o n s t r u c t i o n o f a s m a ll t u n n e l w as j u s t i f i e d b y

th e s e n e ed s. II.

MONETARY CONSIDERATIONS

As i n m o st s i m i l a r c a s e s , t h e m a t t e r o f m o n e ta ry e x ­ p e n d i t u r e w as o f c o n s i d e r a b l e i m p o r ta n c e .

W in d - tu n n e ls may

b e p u r c h a s e d i n a d is a s s e m b le d c o n d i t i o n f o r a fe w th o u s a n d d o lla rs .

A s m a ll t u n n e l , w h ic h may be p l a c e d o n a d e s k , i s

a v a ila b le f o r $750, w ith o u t in s tr u m e n ts . tu n n e l i s v e ry lim ite d in i t s u s e fu ln e s s .

S uch a s m a ll The c o s t o f t h e

s u b j e c t t u n n e l w as e s t i m a t e d a t a p p r o x i m a t e ly $ 1 ,0 0 0 f o r m a t e r i a l , p a r t s , a n d m a c h in in g .

Due t o t h e n a t u r e o f t h e

p r o j e c t , l a b o r o t h e r t h a n m a c h in in g w as n o t c o u n te d i n t h e c o s t. I ll.

COMMERCIAL TESTING

When a n i n s t i t u t i o n o f l e a r n i n g a c q u i r e s a r e l i a b l e

3 p ie c e o f a p p a ra tu s f o r i n s t r u c t i o n a l p u rp o s e s , i t s u se f o r th o s e p u rp o se s i s f r e q u e n t ly i n t e r r u p t e d b y a p p ly in g i t to c o m m e rc ia l t e s t i n g .

'While t h e i n s t i t u t i o n p r o f i t s i n

s e v e r a l w ays t h r o u g h s u c h t e s t s , t h e s t u d e n t i s t h e l o s e r when t h e t e s t s a r e o f a c o n f i d e n t i a l n a t u r e .

F u r th e r , such

t e s t s may se ld o m b e p r o p e r l y i n t e g r a t e d w i t h a p r e s c r i b e d c o u rse .

I n v ie w o f t h e r e l a t i v e l y s m a ll c a p i t a l i n v e s tm e n t

t h e s u b j e c t t u n n e l w as d e s ig n e d t o be u s e f u l i n e le m e n t a r y i n s t r u c t i o n , b u t n o t s u i t e d t o t h e d e t e r m i n a t i o n o f d e s ig n d a ta . IV .

DEFINITIONS OF TERMS AND SYMBOLS

A f t e r B o d y ,— The d o w n stre a m en d o f t h e m o to r f a i r i n g . A ngle o f A t t a c k , — T he a n g le b e tw e e n a r e f e r e n c e l i n e and th e r e l a t i v e v e l o c i t y .

F or a i r f o i l s th e re fe re n c e lin e

j o in s th e le a d in g edge and th e t r a i l i n g

edge.

B a la n c e S y s te m ,— A s y s te m o f b a l a n c e s b y m eans o f w h ic h f o r c e s may be m e a s u r e d . B la d e A n g le ,- - T h e a n g le b e tw e e n t h e a i r f o i l r e f e r e n c e l i n e i n a p r o p e l l e r b la d e and th e p la n e o f r o t a t i o n . B o u n d a ry L a y e r T u b e s ,— S m a ll d i a m e t e r t u b i n g f o r m e a s u r in g p r e s s u r e s i n t h e r e g i o n im m e d ia te ly a d j a c e n t t o t h e s u r f a c e o f a m o d e l. D i f f u s e r , — A r e g i o n , i n a w i n d - t u n n e l , a lo n g w h ic h th e p re s s u re in c re a s e s .

4 D rag F o r c e , — A f o r c e a p p l i e d b y t h e a i r i n t h e d i ­ r e c tio n o f th e r e l a ti v e v e lo c ity v e c to r. D rag S p h e r e ,— A s p h e r e u s e d f o r t h e d e t e r m i n a t i o n o f t h e c r i t i c a l R e y n o ld s Number o f a t u n n e l . 2 Dynamic P r e s s u r e , — A p r e s s u r e e q u a l t o 1 / 3 (°F . F a i r i n g , — A t h i n s h e e t o f m a t e r i a l u se d t o e n c lo s e a ro u g h o b j e c t . Fan M o u n t,— The s t r u c t u r e w h ic h i n d i r e c t l y s u p p o r t s th e f a n .

The m o to r m o u n t.

Fan S e c t i o n , — T h a t s e c t i o n o f t h e t u n n e l w i t h i n w h ic h th e fa n i s e n c lo s e d . Flow D i r e c t i o n I n d i c a t o r , — An i n s t r u m e n t f o r d e t e r ­ m in in g t h e d i r e c t i o n o f t h e a v e r a g e v e l o c i t y v e c t o r . L i f t F o r c e ,— A f o r c e a p p lie d by th e a i r i n a d i ­ r e c t i o n n o rm a l t o t h e r e l a t i v e v e l o c i t y v e c t o r . M o to r M o u n t,— The s t r u c t u r e w h ic h s u p p o r t s t h e m o to r . S e t t l i n g C h a m b e r,— The r e g i o n o f l a r g e c r o s s s e c t i o n ­ a l a r e a j u s t u p s tr e a m o f t h e t h r o a t . S t a t i c P r e s s u r e , — The a m b ie n t p r e s s u r e o f t h e a i r . S t r a i g h t e n i n g F a n e s , — F a n e s , t h e p u r p o s e o f w h ic h i s t o r e d i r e c t t h e a i r f lo w . S p in n e r ,— A f a l s e

s t r u c t u r e m o u n te d on a n d i n f r o n t

o f a p r o p e l l e r f o r g u id a n c e o f t h e a i r s t r e a m . T h r o a t , — The s m a l l e s t c r o s s s e c t i o n a l a r e a i n t h e w in d -tu n n e l.

5 T o r q u e ,— The p r o d u c t o f a f o r c e a n d a d i s t a n c e . T o rq u e A rm ,— The d i s t a n c e in v o lv e d i n t o r q u e . T u r n in g V a n e s ,— C u rv ed m em bers u s e d t o g u id e t h e a i r i n f lo w in g a ro u n d a c o r n e r . A— An a r e a . C— A c o e f f i c i e n t , CL— l i f t c o e f f i c i e n t , CD— d ra g c o e ffic ie n t. D— D rag f o r c e , p o u n d s .

D ia m e te r .

32^— E n e rg y R a t i o . F— A f o r c e . L— L i f t f o r c e , p o u n d s . M—M om ent, f o r c e t im e s d i s t a n c e . N .R .— R e y n o ld s N um ber, n o n - d i m e n s i o n a l . N— R o t a t i v e s p e e d , r e v . p e r m i n . , r e v . p e r s e c . R— Gas c o n s t a n t , 5 3 .3 f t . / ° R

fo r a ir.

T— T o rq u e , A b s o lu te t e m p e r a t u r e °R . V— V e l o c i t y , f . p . s . , m .p .h . X— A d i s t a n c e . g — G ra v ity a c c e l e r a ti o n . p—P re s s u re .

3 2 .2 f t . / s e c .

W e ig h t,

q— Dynamic P r e s s u r e , v — S p e c i f i c v o lu m e , c u . f t . / l b . w— S p e c i f i c w e i g h t , l b s . / c u . f t . — A ngle o f A t t a c k . — B la d e A n g le .

g

6 so 3 c —M ass D e n s i t y , s l u g s / f t . V.

ORGANIZATION OF THE REMAINDER OF THE THESIS

C h a p te r I I .

C h a p te r I I c o n s i s t s o f a s h o r t resu m e o n

th e h i s t o r y o f w in d -tu n n e ls and ty p e s .

The b a s i c d e s i g n o f

t h e s u b j e c t t u n n e l , a n d t h e r e a s o n s f o r t h e d e s ig n s e l e c t i o n a re d is c u s s e d . C h a p te r I I I .

I n t h i s c h a p te r th e s p e c i f i c d e s ig n o f

th e tu n n e l i s e x p la in e d .

The g e n e r a l i z e d s i z e s o f p a r t s a r e

s p e c i f i e d a lo n g w i t h some o f t h e c h a r a c t e r i s t i c s w h ic h w e re d e s ire d . C h a p te r IV .

A s h o r t d e s c r i p t i o n o f t h e m e th o d s and

p r o b le m s o f c o n s t r u c t i o n i s g iv e n i n C h a p te r IV . C h a p te r V.

C h a p te r V d e s c r i b e s t h e i n s t r u m e n t s w h ic h

w e re d e s ig n e d a n d c o n s t r u c t e d a s a c c e s s o r i e s t o t h e t u n n e l . The p ro b le m s i n c i d e n t t o t h e i r c o n s t r u c t i o n a r e e n u m e r a te d . C h a p te r V I.

T h is c h a p t e r t r e a t s o f t h e a c t u a l c a l i ­

b r a tio n o f th e tu n n e l.

The r e s u l t s o f t h e c a l i b r a t i o n a r e

a ls o in c lu d e d . C h a p te r V I I .

I n C h a p te r V II t h e t h e s i s i s su m m arized

an d c o n c l u s i o n s a r e d ra w n .

R eco m m en d atio n s f o r f u t u r e w ork

a r e m ad e. The B i b l i o g r a p h y f o l l o w s C h a p te r V I I . A p p e n d ix A.

The c a l i b r a t i o n d a t a , c a l c u l a t i o n s , an d

r e s u l t s a r e c o n t a i n e d i n A p p e n d ix A.

A p p e n d ix B . and p h o to g ra p h s .

A p p e n d ix B c o n t a i n s t h e v a r i o u s d r a w in g s C o m p lete i n f o r m a t i o n i s g i v e n , fro m w h ic h

a d u p l i c a t e t u n n e l c o u ld h e c o n s t r u c t e d .

The d ra w in g s a r e

f o llo w e d b y a b i l l o f m a t e r i a l s an d a s t a t e m e n t o f e x p e n d i­ tu re s .

CHAPTER I I A BRIEF ON WIND-TUNNEL HISTORY The m o d em w i n d - t u n n e l i s t h e o u tg r o w th o f a m eth o d o f e x p e r i m e n t a l p r o c e d u r e w h ic h h a d a s i t s o r i g i n t h e u s e o f n a t u r a l a i r c u r r e n t s t o p ro d u c e f o r c e s on o b j e c t s u n d e r t e s t . V a r io u s m e th o d s w e re e m p lo y e d .

Some e x p e r i m e n t e r s d ro p p e d

t h e i r o b j e c t s t h r o u g h t h e a i r fro m a h ig h p o s i t i o n a n d o b ­ se rv e d th e r e s u l t a n t a c tio n s .

O th e r s m o u n te d t h e o b j e c t s on

v a r i o u s d e v i c e s w h ic h w e re t h e n p l a c e d i n a n a t u r a l a i r c u rre n t.

O b s e r v a ti o n s w ere t h e n made a s t o f o r c e s , m om ents,

m o ti o n s , e t c . o f t h e o b j e c t .

S t i l l o t h e r s m ade u s e o f t h e

p r i n c i p l e o f t h e pen d u lu m b y a f i x i n g t h e o b j e c t t o t h e e n d o f a lo n g c o rd o r w i r e . I n g e n e r a l , t h e s e e a r l y t e s t s w e re o f r a t h e r p o o r q u a l i t y due t o t h e l a c k o f c o n t r o l o f t h e a i r s t r e a m .

One

o f t h e e a r l y a t t e m p t s a t c o n t r o l w as t h e L a n g le y W h ir lin g Arm.

I n t h i s a p p a r a t u s t h e o b j e c t u n d e r t e s t w as a t t a c h e d

t o t h e e n d o f a m em ber w h ic h w as t h e n r o t a t e d a b o u t a v e r tic a l a x is .

A s te a m -p o w e re d t h r e s h i n g m a c h in e w as t h e

s o u r c e o f m o tio n an d t h e r a t e o f r o t a t i o n w as c o n t r o l l a b l e . Two o f t h e d i s a d v a n t a g e s o f t h i s u n i t w ere t h e d e v e lo p m e n t o f c e n t r if u g a l f o r c e and th e c o n tin u a l d is tu r b a n c e o f th e a i r due t o t h e r o t a t i o n o f t h e a rm . F r e e - a ir t e s t s a re s t i l l u sed e x te n s iv e ly b u t th e

9 o b j e c t u n d e r t e s t i s now m o u n te d on a m o ving m a c h in e s u c h a s an a i r p l a n e , a u to m o b i le , o r a r a i l c a r r i a g e .

In th e s e c ase s

t h e m o tio n i s c o n t r o l l a b l e w i t h i n l i m i t s w h ic h a r e som ew hat n a rro w .

F o r p r e l i m i n a r y d a t a t h e w i n d - t u n n e l i s now t h e

m o st common s o u r c e o f i n f o r m a t i o n . I .

WIND-TUNNEL CLASSIFICATIONS

W in d - tu n n e ls a r e c l a s s i f i e d u n d e r m any h e a d i n g s . m o st

The

common o f t h e s e a r e h e r e l i s t e d and d e f i n e d . 1.

Open C i r c u i t .

The o p en c i r c u i t t u n n e l i s o n e i n

w h ic h t h e a i r e n t e r s a t on e e n d , l e a v e s a t t h e o t h e r e n d , a n d i s n o t c o n d u c te d b a c k t o t h e e n t r a n c e . 2.

C lo s e d C i r c u i t .

i n w h ic h t h e same a i r i s

A c l o s e d c i r c u i t t u n n e l i s one

u sed o v e r and o v e r, th e tu n n e l

b e in g a t y p e o f e n d l e s s d u c t .

C lo s e d c i r c u i t t u n n e l s a r e

d e s ig n a te d a s s in g le r e t u r n , m u ltip le r e t u r n , o r a n n u la r re tu rn ty p e s . 3. w h ic h

th e

C lo s e d T h r o a t .

A c lo s e d t h r o a t tu n n e l i s one in

w o rk in g , o r t e s t s e c t i o n , i s b o u n d e d b y s o l i d

w a lls . OPQfl T h r o a t . n o t g u id e d

I n an o p e n t h r o a t t u n n e l t h e a i r i s

th r o u g h t h e t e s t s e c t i o n b y s o l i d w a l l s a s i s t h e

c a se in th e c lo s e d t h r o a t ty p e .

10 5*

C i r c u l a r , O c t a g o n a l , H e x a g o n a l, R e c t a n g u l a r .

The

u s e o f t h e s e t e r m s i n c o n n e c tio n w i t h w i n d - t u n n e l s d e s i g ­ n a t e s t h e fo rm o f t h e b o u n d a r i e s o f t h e c r o s s s e c t i o n a l a r e a o f th e th r o a t. 6.

V i s u a l g lo w .

V i s u a l f lo w t u n n e l s a r e u s e d p r i ­

m a r i l y f o r o p t i c a l l y o b s e r v i n g t h e f lo w p h en o m en a.

T h e se

phenom ena a r e made v i s i b l e w i t h t h e a i d o f w o o l t u f t s , o r b y a n y one o f s e v e r a l m e th o d s o f p r o d u c in g v i s i b l e 7.

F o rc e M e a s u re m e n t.

fu m e s .

M ost s u b s o n ic t u n n e l s a r e

u s e d p r i m a r i l y f o r t h e p u r p o s e o f d e te r m i n i n g t h e f o r c e s an d m om ents w h ic h a r e a p p l i e d t o t h e m o d e l b y t h e a i r s t r e a m . 8*

H o riz o n ta l.

V e rtic a l.

T h e se te r m s m ay r e f e r t o

e i t h e r o f th r e e ty p e s o f c o n s tr u c tio n .

F o r th e open c i r c u i t

tu n n e l th e y r e f e r to th e a t t i t u d e o f th e a x is o f th e tu n n e l. I n t h e c l o s e d r e t u r n t u n n e l t h e y m ay r e f e r t o e i t h e r t h e a t t i t u d e o f t h e t h r o a t a x i s , o r t o t h e p l a n e w h ic h c o n t a i n s th e ax es o f a l l s e c tio n s o f th e tu n n e l. A tm o s p h e r ic .

V a ria b le D e n s ity .

The te r m s a tm o s ­

p h e r i c , an d v a r i a b l e d e n s i t y , r e f e r t o t h e r e l a t i v e p r e s s u r e u n d e r w h ic h t h e t u n n e l may o p e r a t e .

I n t h e a tm o s p h e r ic

tu n n e l th e p re s s u re a t any s e c tio n v a rie s b u t l i t t l e t h a t o f t h e f r e e a tm o s p h e r e .

fro m

The v a r i a b l e d e n s i t y t u n n e l i s

o f n e c e s s i t y a s e a l e d u n i t a n d t h e p r e s s u r e w i t h i n i t may b e

11 c o n t r o l l e d w i t h i n w id e l i m i t s d e p e n d e n t u p o n t h e s t r e n g t h o f t h e t u n n e l s t r u c t u r e a n d t h e p o w er a v a i l a b l e f o r p r e s s u r e c o n tro l, 10.

W a te r T u n n e l .

I n some i n s t a n c e s i t

i s advan­

t a g e o u s t o h av e a t e s t i n g m edium o f h i g h e r d e n s i t y t h a n i s a v a ila b le w ith a i r .

W a te r t u n n e l s h a v e b e e n u s e d s u c c e s s ­

f u l l y i n su c h c a s e s . F u ll- S c a le .

A fe w t u n n e l s h a v e b e e n b u i l t i n

w h ic h a n a c t u a l a i r p l a n e may be t e s t e d .

To d a t e no r e a l l y

h i g h s p e e d t u n n e l s h a v e b e e n made i n su c h s i z e . 12•

S u b s o n ic .

S u p e rs o n ic .

A s u b s o n ic t u n n e l i s one

i n w h ic h t h e s p e e d o f t h e a i r t h r o u g h t h e t e s t s e c t i o n i s l e s s t h a n t h e s p e e d o f so u n d i n t h e a i r a t t h a t s e c t i o n .

In

th e s u p e rs o n ic tu n n e l th e sp eed o f th e a i r th ro u g h th e t e s t s e c t i o n may be g r e a t e r t h a n t h e s p e e d o f so u n d i n t h a t a i r . To d a t e , a l l s u p e r s o n i c t u n n e l s w h ic h h a v e b e e n b u i l t h a v e h a d r e l a t i v e l y s m a ll t e s t s e c t i o n s due t o t h e f a c t t h a t t h e y consum e enorm ous am o u n ts o f pow er o r o f a i r .

S u p e r s o n ic

t u n n e l s may b e o p e r a t e d c o n t i n u o u s l y b y m eans o f h i g h - o u t p u t b lo w e rs , o r i n t e r m i t t e n t l y by th e u se o f la r g e s to r a g e ta n k s w h ic h may be e i t h e r e v a c u a t e d , o r pumped f u l l o f a i r . 13.

F ix e d M o d e l.

F re e F l i g h t .

m o d e ls w h ic h a r e a t t a c h e d r i g i d l y t o

M ost t u n n e l s em p lo y

some s u p p o r t m em ber so

12 t h a t t h e y re m a in s t a t i o n a r y i n s p a c e ,

A few t u n n e l s h a v e

b e e n b u i l t i n w h ic h t h e m o d e ls a r e la u n c h e d i n t o f r e e f l i g h t . T h e se a r e u s u a l l y u s e d t o s tu d y s t a b i l i t y c h a r a c t e r i s t i c s o f t h e m o d e ls . 14.

T h re e D im e n s io n a l.

Two D im e n s io n a l»

T h ese

d e s i g n a t i o n s i n d i c a t e t h e r e l a t i v e m o tio n s o f t h e a i r i n p a s s i n g o v e r t h e m o d e l. d im e n s io n a l f l o w .

The u s u a l t u n n e l e m p lo y s t h r e e

I n some c a s e s a t u n n e l i s made so t h a t a

w in g o r o t h e r t e s t ite m w i l l s p a n t h e e n t i r e w id th o f t h e t e s t s e c tio n .

I n s u c h c a s e s t h e f lo w i n t h e t e s t s e c t i o n i s

e s s e n t i a l l y tw o d im e n s io n a l i n t h a t no f lo w c a n o c c u r a ro u n d t h e e n d s o f t h e w in g . X I.

BALANCE SYSTEMS

B a la n c e s y s te m s a r e u s u a l l y c l a s s i f i e d i n t h r e e w a y s, (1 ) b y t h e m eth o d u s e d t o s u p p o r t t h e m o d e l; (2 ) b y t h e num­ b e r o f f o r c e a n d moment c o m p o n e n ts w h ic h m ay be m e a s u re d ; a n d (3) b y t h e s y s te m o f f o r c e m e a s u re m e n t. 1.

M eth o d s o f S u p p o r t .

i n t h e s u p p o r t o f w i n d - t u n n e l m o d e ls .

Many m e th o d s h a v e b e e n u s e d The c h o ic e o f s u p p o r t

s y s te m i s d e p e n d e n t upon (1 ) t h e d e s i r e d a c c u r a c y ; (2 ) t h e e a s e w i t h w h ic h a d j u s t m e n t s may b e m ade; (3 ) t h e s i z e o f t h e t e s t m o d e l; a n d (4 ) t h e t y p e o f t u n n e l i n v o l v e d . F o r s u b s o n ic t e s t w o rk on s m a ll m o d e ls a s im p le w ir e

13 s u s p e n s io n s y s te m i s so m e tim e s e m p lo y e d .

T h is ty p e o f

s u s p e n s io n i s u s u a l l y d i f f i c u l t t o a d j u s t a n d m a i n t a i n i n a li g n m e n t .

I t h a s r e l a t i v e l y p o o r a c c u r a c y due t o a i r f l o w

i n t e r f e r e n c e c a u s e d b y t h e w i r e s , a n d due t o w ir e v i b r a t i o n . The m ore common s u p p o r t f o r s u b s o n ic t e s t i n g c o n s i s t s o f one o r m ore to w e r s w h ic h e x te n d upw ard i n t o t h e t e s t s e c t i o n o f th e tu n n e l.

T h is m eth o d r e s u l t s i n f a r l e s s v i b r a t i o n an d

i n t e r f e r e n c e , a n d g i v e s b e t t e r a c c u r a c y an d e a s e o f a d j u s t ­ m e n t.

M o d e ls m ay b e q u i c k l y i n s t a l l e d o r rem o v e d , a n d n e e d

n o t be u p s i d e down a s i s u s u a l l y n e c e s s a r y i n t h e w ir e s u s ­ p e n s io n s y s te m . F o r s u p e r s o n i c t e s t s t h e m o d e ls a r e u s u a l l y m o u n ted o n a t a i l - s t i n g , w h ic h i s a s t r u c t u r a l m em ber e x te n d in g down s tr e a m fro m t h e t a i l o f t h e m o d e l. C om ponents t o b e m e a s u r e d .

The s i m p l e s t k i n d o f

m e a su re m e n t o n a m o d el w o u ld be t h e d e t e r m i n a t i o n o f g r o s s d r a g o r w in d r e s i s t a n c e .

The m o st c o m p lex c o m b in a tio n

u s u a l l y e n c o u n te r e d i s t h e d e t e r m i n a t i o n o f t h e s i x com­ p o n e n ts l i f t ,

d r a g , s i d e f o r c e , p i t c h i n g m om ent, r o l l i n g

m om ent, an d y a w in g m om ent.

A s u p p o r t s y s te m m ay be d e s ig n e d

th r o u g h w h ic h a n y one o r m ore o f t h e s e co m p o n e n ts m ay be m e a s u re d . S y ste m s o f F o rc e M e a s u re m e n t. o f a e ro d y n a m ic t e s t i n g

In th e e a r ly y e a rs

s im p le s p r i n g - t y p e d e v i c e s w e re i n

14 common u s e f o r m e a s u r in g t h e f o r c e s e n c o u n t e r e d .

T h e se

s y s te m s h a d t h e d i s a d v a n t a g e s o f r e q u i r i n g f r e q u e n t r e c a l i ­ b r a t i o n , o f d e v e lo p in g e x c e s s i v e v i b r a t i o n , a n d o f a ll o w i n g t h e m o d el t o move a n d t h u s u p s e t t h e a li g n m e n t .

S p r in g

s y s te m s a r e now i n t h e d i s c a r d e x c e p t f o r t h e s i m p l e s t t y p e o f t e s t i n g o r d e m o n s tr a ti o n w o rk . The m o st common t y p e o f s y s te m i n u s e t o d a y i n v o l v e s t h e u s e o f b a la n c e beam s a lo n g w h ic h p o i s e s a r e m oved f o r f i n e a d ju s tm e n ts .

The p o i s e may b e moved b y h a n d , o r i t m ay

b e c o n t r o l l e d a u t o m a t i c a l l y b y a n e l e c t r i c m o to r w h ic h i s a c t u a t e d b y c o n t a c t p o i n t s on t h e beam a n d t h e f r a m e . I n r e c e n t y e a r s m ore e l a b o r a t e s y s te m s h a v e b e e n d e ­ v e lo p e d f o r d e te r m in in g t h e f o r c e c o m p o n e n ts .

Among t h e s e

a r e t h e s t r a i n - g a g e t y p e , an d t h e e l e c t r o - m a g n e t i c s y s te m . iii .

m m - T m m i c o m p o n e n ts

I t seem s a p p r o p r i a t e a t t h i s p o i n t t o g iv e a s h o r t d e s c r i p t i o n o f t h o s e m a jo r t u n n e l co m p o n e n ts w h ic h h a v e n o t y e t b e e n m e n tio n e d . A ll w in d -tu n n e ls r e q u ir e d i f f u s e r s e c tio n s .

In th e s e

s e c t i o n s t h e f lo w i s c o n t r o l l e d b y v a r i a t i o n s i n t h e c r o s s s e c tio n a l a re a .

F o r s u b s o n ic t u n n e l s , t h e d i f f u s e r s e c t i o n

c a u s e s a d e c re a s e in v e l o c i t y and an in c r e a s e i n p r e s s u r e w h ic h i s a c c o m p lis h e d b y an i n c r e a s e i n a r e a .

For su p e r­

s o n ic t u n n e l s t h e i n c r e a s e i n p r e s s u r e i s a c c o m p a n ie d b y a

15 d e c r e a s e i n v e l o c i t y , b u t t h e s e phenom ena a r e c a u s e d b y a d e c re a se in a re a o f th e d if f u s e r s e c tio n . S u b s o n ic t u n n e l s make u s e o f a s e t t l i n g c h am b er t o h e l p damp o u t i r r e g u l a r i t i e s i n t h e f lo w .

The s e t t l i n g

ch am ber i s s im p ly a r e g i o n o f c o n s t a n t a r e a u p s tr e a m o f t h e th ro a t. The t h r o a t o f a w i n d - t u n n e l i s a r e g i o n o f r e d u c e d a r e a w h e r e in t h e a i r v e l o c i t y i s c a u s e d t o b e h i g h .

In th e

s u b s o n ic t u n n e l t h i s i s t h e r e g i o n o f maximum v e l o c i t y , and t e s t s a r e c o n d u c te d h e r e i n .

I n th e s u p e rs o n ic tu n n e l th e

t h r o a t i s t h e r e g i o n i n w h ic h t h e v e l o c i t y o f t h e a i r b e ­ com es e q u a l i n m a g n itu d e t o t h e v e l o c i t y o f so u n d i n t h a t a ir.

T e s t s i n t h e s e t u n n e l s a r e c o n d u c te d i n a r e g i o n

d o w n stre am o f t h e t h r o a t w h e r e in t h e v e l o c i t y h a s becom e s u p e r s o n i c due t o t h e i n c r e a s e i n c r o s s s e c t i o n a l a r e a . IV .

THE SUBJECT TUNNEL

I n v ie w o f t h e p r e c e d i n g d i s c u s s i o n t h e s u b j e c t t u n ­ n e l m ay b e c l a s s i f i e d b y t h e t e r m s , 1.

Low s u b s o n ic v e l o c i t y .

2.

Open r e c t a n g u l a r a tm o s p h e r ic t h r o a t w i t h h o r i ­ z o n t a l f lo w .

3.

C lo s e d s i n g l e v e r t i c a l r e t u r n .

4.

F o rc e m e a su re m e n t t y p e w i t h f i x e d m o d e l. «

The t u n n e l b a la n c e s y s te m i s

c a p a b le o f m e a s u r in g

16 f i v e c o m p o n e n ts , t h o s e o f l i f t ,

d r a g , p i t c h i n g m om ent, r o l l ­

i n g m om ent, a n d yaw ing m om ent.

I t i s com posed o f a b u i l t - u p

fra m e w h ic h s u p p o r t s t h e e n t i r e s y s te m , i s i t s e l f s u p p o r te d b y t h e t u n n e l , a n d i s r e a d i l y re m o v a b le fro m t h e t u n n e l . F o r c e s a r e m e a s u re d b y beam a n d r i d e r a r r a n g e m e n ts .

A tri­

a n g u l a r l i f t - f r a m e i s s u p p o r te d b y w i r e s w h ic h p a s s t o t h r e e l i f t beam s w h ic h a r e a t t a c h e d t o t h e s u p p o r t f r a m e . th e l i f t - f r a m e i s a te e -s h a p e d d ra g -fra m e .

B elow

S u p p o rt f o r t h e

d r a g - f r a m e i s o b t a i n e d b y d i r e c t w ir e c o n n e c ti o n s t o t h e lift-fra m e .

The d r a g beam s a r e a t t a c h e d t o t h e s u p p o r t

f r a m e , a n d w i r e s a r e u s e d t o t r a n s m i t t h e d r a g f o r c e s fro m t h e d r a g - f r a m e t o t h e d r a g b e am s.

The d r a g beam s a r e c a l i ­

b r a t e d t o f i v e o n e - t h o u s a n d t h s o f a p o u n d , t h e l i f t beam s t o o n e o n e - h u n d r e th o f a p o u n d . The m o d el s u p p o r t to w e r i s a t t a c h e d t o t h e l e g o f t h e t e e o f t h e d r a g - f r a m e an d e x t e n d s upw ard t h r o u g h t h e l i f t fra m e an d t h e s u p p o r t fra m e i n t o t h e t h r o a t o f t h e t u n n e l . The a n g le o f a t t a c k o f t h e m o d el m ay b e v a r i e d b y s u i t a b l e m ech an ism w h ic h e x te n d s downward th r o u g h t h e to w e r t o a co n ­ t r o l s ta tio n

j u s t b e lo w t h e d r a g - f r a m e .

The m o d el m ay be

yaw ed o n t h e to w e r b u t t h e c o n t r o l s t a t i o n f o r t h i s a d j u s t ­ m en t i s a t t h e t o p o f t h e t o w e r . Some o f t h e c o n s i d e r a t i o n s w h ic h d e te r m in e d t h e t y p e o f d e s i g n u s e d w ere d i s c u s s e d i n C h a p te r I .

The c h o ic e o f a

c l o s e d r e t u r n s y s te m w as d i c t a t e d b y a d e s i r e t o k e e p t h e

17 t u n n e l s m a ll an d co m pact an d t o u t i l i z e t h e e n e r g y o f t h e a i r a f t e r i t h ad p a s s e d th ro u g h th e t h r o a t .

R e u s in g t h e a i r

p e rm its th e a tta in m e n t o f a h ig h e r t h r o a t v e l o c i t y f o r a g iv e n i n p u t p o w er t h a n c o u ld be o b t a i n e d i f t h e a i r w ere u s e d o n c e and t h e n d i s c a r d e d . P lyw ood c o n s t r u c t i o n w as c h o s e n b e c a u s e o f i t s r e l a ­ t i v e l y lo w c o s t , d u r a b i l i t y , a n d n o i s e d am p en in g q u a l i t i e s . The r e c t a n g u l a r c r o s s s e c t i o n w as c h o s e n i n o r d e r t o k e e p t h e w o rk o f f a b r i c a t i o n a t a m inim um . The p r i n c i p l e d im e n s io n s o f t h e t u n n e l w e re d e t e r ­ m in e d o n t h e b a s i s o f a d e s i r e t o h a v e a t u n n e l a s l a r g e a s p o s s i b l e a n d s t i l l be r e a d i l y m o v ab le w i t h i n t h e l a b o r a t o r y , and f o r th e o p e r a to r to be a b le to re a c h a l l p a r t s o f th e t u n n e l w h ile s t a n d i n g on t h e f l o o r . The c h o ic e o f s h e e t - m e t a l c o n s t r u c t i o n a t t h e f a n w as d i c t a t e d b y t h e n e c e s s i t y o f h a v in g t r a n s i t i o n c o n v e r t fro m r e c t a n g u l a r t o

s e c tio n s to

c ir c u la r c ro s s s e c tio n .

D u rin g t h e e a r l y s t a g e s o f d e v e lo p m e n t a s t a r t w as m ade on t h e d e s i g n o f a f a n f o r t h e t u n n e l .

T h is w as d i s ­

c a r d e d w hen i t w as f o u n d t h a t a H a r t z e l l m in e f a n c o u ld b e m o d if i e d t o f i t t h e t u n n e l n e e d s .

The b u i l d i n g o f a s p e c i a l

f a n w o u ld h a v e e n t a i l e d c o n s i d e r a b l e e x p e n s e .

M o d ific a tio n

c o s t s on a t h i r t y - s i x i n c h H a r t z e l l f a n h a d l i t t l e

e f f e c t on

t h e p u r c h a s e p r i c e w h ic h w as w e l l u n d e r t h e e s t i m a t e d c o s t o f a s p e c ia l fa n .

18 S in c e t h e t u n n e l w as d e s ig n e d p r i m a r i l y f o r i n ­ s t r u c t i o n a l p u r p o s e s , t h e m o to r w as m o u n ted so a s t o c o n v e r t i t i n t o a d y n a m o m ete r.

M o u n tin g f i x t u r e s w ere d e s ig n e d s u c h

t h a t t h e m o to r fra m e w as m o u n te d on b a l l b e a r i n g s an d w as f r e e to re v o lv e a b o u t th e s h a f t c e n t e r l i n e .

A c tu a l r o t a t i o n

o f t h e fra m e w as p r e v e n t e d - b y m eans o f a t o r q u e a r k r i g i d l y a tta c h e d to i t . beam b a l a n c e .

The o u t e r en d o f t h e arm w as s u p p o r t e d b y a T h is t o r q u e b a la n c e w as c o n v e r t e d fro m a

C h a t i l l o n c o u n ti n g s c a l e f o r w h ic h new p o i s e s an d beam r i d e r s w e re d e s i g n e d .

The o r i g i n a l m a rk in g s w ere r e t a i n e d

o n t h e beam , a n d w ith t h e new r i d e r e a c h i n d e x s p a c e r e p r e ­ s e n t s o n e - e i g h t h o f an o u n c e t o r q u e f o r c e .

To c o m p le te t h e

d yn am om eter i n s t a l l a t i o n a t a c h o m e t e r w as n e e d e d .

S in c e t h e

m o to r d i d n o t r e a d i l y l e n d i t s e l f t o t h e a tta c h m e n t o f a m e c h a n ic a l t a c h o m e t e r , a Frahm v i b r a t i n g r e e d ta c h o m e t e r w as o b ta in e d . it

T h is i n s t r u m e n t i s p o r t a b l e an d i s u s e d o n l y when

i s d e s i r e d t o o b t a i n t h e p o w er i n p u t t o t h e f a n .

CHAPTER I I I DESIGN OF THE TUNNEL The o v e r - a l l c o n s i d e r a t i o n s i n t h e d e s i g n o f t h e t u n n e l w e re s t a t e d i n C h a p te r I .

The p u r p o s e o f t h i s c h a p ­

t e r i s t o e n l a r g e u p o n , a n d e x te n d , t h o s e c o n s i d e r a t i o n s , a n d t o e x p l a i n how t h e f i n a l d e s i g n w as a t t a i n e d . I.

SIZE SPECIFICATIONS

C o n s id e ra tio n s o f c o s t and sp a ce a v a ila b le f o r th e t u n n e l d i c t a t e d t h a t i t be s m a ll an d s e m i - p o r t a b l e .

An

a r b i t r a r y l e n g t h l i m i t o f a b o u t tw e lv e f e e t w as s e l e c t e d . T he c h o ic e o f t h r o a t c e n t e r l i n e h e i g h t w as b a s e d upon t h e d e s i r e f o r c o n v e n ie n c e i n h a n d li n g t h e m o d e ls .

The h e i g h t

c h o s e n w as a b o u t f i f t y - e i g h t i n c h e s fro m t h e f l o o r .

H aving

d e c id e d t o u s e p ly w o o d f o r t h e w a l l s t r u c t u r e i t w as c o n ­ v e n i e n t an d e c o n o m ic a l t o c h o o se a c o n s t a n t t u n n e l w id th o f a b o u t tw o f e e t .

The c o n t r a c t i o n r a t i o w as c h o s e n a s two t o

one s i n c e t h i s w o u ld r e s u l t i n a f a i r l y r e a s o n a b l e f lo w i n t h e t h r o a t w h ic h w o u ld n o t be s u f f i c i e n t l y r e f i n e d t o b e o f v a l u e f o r c o m m e rc ia l t e s t i n g . H a v in g s e l e c t e d t h e f o r e g o i n g a p p ro x im a te v a l u e s a ro u g h s k e t c h o f t h e t u n n e l w as m ade.

From t h i s i t becam e

e v i d e n t t h a t a f a n d i a m e t e r o f a b o u t tw o a n d o n e - h a l f f e e t c o u ld be u s e d , a n d t h a t t h e v e r t i c a l d im e n s io n o f t h e

20 s e t t l i n g ch am b er c o u ld be a b o u t t h i r t y - t w o i n c h e s .

The

t h i r t y - t w o i n c h v a lu e w as oho s e n a s t h e d im e n s io n o f t h e s id e w a ll p a n e l.

A llo w a n c e f o r a s s e m b ly o f t h e t o p and

b o tto m p a n e l s r e s u l t e d i n a v e r t i c a l i n s i d e d im e n s io n o f t h i r t y in c h e s .

The c h o ic e o f c o n s t a n t w id th an d a tw o t o

one c o n t r a c t i o n r a t i o

c o n tr o lle d th e v e r t i c a l th r o a t d i­

m e n s io n w h ic h w as fo u n d t o b e f i f t e e n i n c h e s .

T hus t h e

t h r o a t a r e a w as tw o a n d o n e - h a l f s q u a r e f e e t . The a p p ro x im a te f a n d i a m e t e r w as t h e n b a s e d on a f a n d is c a re a eq u al to th a t o f th e s e t tl i n g 2(2i)

c h a m b e r.

T h u s,

(D2 - a2 )

An a llo w a n c e o f o n e f o o t w as m ade f o r t h e d i a m e t e r o f t h e m o to r f a i r i n g s i n c e i t h a d b e e n d e c id e d t o h o u s e t h e m o to r w ith in th e tu n n e l.

T h u s,

D2 - 20 4 1 : 7 .3 7 “ TT D = 2 .7 1 5 f t .

- 32— i n c h e s

T h is v a l u e w as c o n s i d e r e d s u f f i c i e n t l y c l o s e t o t h e i n i t i a l a s s u m p tio n o f a b o u t tw o a n d o n e - h a l f f e e t .

B e c a u se o f t h e

t y p e o f c o n s t r u c t i o n t o be u s e d , a n d t h e p r o b a b i l i t y o f m oving t h e t u n n e l d u r i n g r e a r r a n g e m e n t o f l a b o r a t o r y e q u ip ­ m e n t, a r a d i a l b l a d e c l e a r a n c e o f o n e - h a l f i n c h w as co n ­ s id e re d a d v is a b le .

The d i a m e t e r o f t h e f a n s e c t i o n w as t h e n

a r b i t r a r i l y ch o sen a s t h i r t y - t h r e e in c h e s and t h a t o f th e

21 fa n a s th ir ty - tw o in c h e s . The f a n w as t h e n l o c a t e d a s c l o s e t o t h e d o w n stre am s i d e o f t h e t h r o a t a s w as c o n v e n i e n t .

The o t h e r s e c t i o n s o f

t h e t u n n e l w ere s k e tc h e d i n so a s t o h a v e a n e a r l y u n if o r m v a r i a t i o n i n t u n n e l a r e a fro m t h e d o w n stre am s i d e o f t h e t h r o a t , th r o u g h t h e f a n s e c t i o n , t o t h e s e t t l i n g c h a m b e r. The f i n a l t u n n e l d ra w in g s w e re t h e n made on t h e b a s i s o f t h i s s k e t c h w i t h due a llo w a n c e f o r p ro b le m s o f s t r u c t u r e a n d c o n s tru c tio n .

The l e n g t h o f t h e t h r o a t w as made s h o r t so a s

t o a v o id e x c e s s i v e l o s s due t o f lo w d i v e r g e n c e . The t h r o a t c o n t r a c t i o n w as a c c o m p lis h e d b y u s i n g tw o c i r c u l a r q u a d r a n t s , t h e c o n t r a c t i o n b e in g i n t h e v e r t i c a l p l a n e o n l y a n d e n d in g a t t h e o p e n t e s t s e c t i o n .

S ubsequent

t e s t i n g o f t h e t u n n e l show ed t h a t t h i s w as p o o r d e s i g n p r o ­ c e d u r e a s i t r e s u l t e d i n e x c e s s i v e f lo w d i v e r g e n c e .

T h is

d i v e r g e n c e w as a lm o s t e l i m i n a t e d b y t h e l a t e r i n s t a l l a t i o n o f a m o d if i e d t h r o a t s e c t i o n

( F ig u r e 1 5 ) .

In l i n e w ith th e d e s ir e f o r s im p lic ity o f con­ s t r u c t i o n , th e tu r n in g v a n es f o r th e f o u r c o rn e rs o f th e t u n n e l w e re d e s ig n e d t o be c i r c u l a r q u a d r a n t s o f s h e e t m e ta l. d e s ig n .

I t w as r e a l i z e d a t t h a t tim e t h a t t h i s w as n o t good H o w ev er, t h e i n t e n t i o n w as t o g e t t h e t u n n e l i n t o

o p e r a t i o n a s so o n a s p o s s i b l e a n d t h e n d e te r m in e t h e l o s s e s due t o t h e s e v a n e s .

The v a n e s w e re t h e n t o be r e p l a c e d w i t h

p r o p e r l y d e s ig n e d v a n e s a d j u s t e d t o t h e p r o p e r a t t i t u d e .

22 T h is p r o c e s s h a s n o t y e t b e e n a c c o m p lis h e d a n d i s o n e o f t h e recom m ended p r o c e d u r e s f o r f u t u r e s t u d y . II.

VELOCITY SPECIFICATIONS AND POWER REQUIREMENTS The c h o ic e o f a i r v e l o c i t y i n t h e t h r o a t w as a r b i ­

tra ry .

A maximum v a lu e o f s i x t y m i l e s p e r h o u r (8 8 f t . / s e c . )

w as s e l e c t e d on t h e b a s i s o f p a s t e x p e r i e n c e w i t h s m a ll t u n ­ n e ls . The p o w er r e q u i r e d w as c a l c u l a t e d o n t h e b a s i s o f t h e c h an g e i n momentum o f t h e a i r a n d t h e i n t r o d u c t i o n o f r e a s o n ­ a b le c o e f f i c i e n t s t o a c c o u n t f o r l o s s e s . Assumed f a n l o s s e s , 26% Assum ed t u n n e l l o s s e s , 15% S e t t l i n g ch am b er v e l o c i t y =

th r o a t v e lo c ity )

=

44 f . p . s . A i r f lo w ,

z 2 .5 ( 8 8 ) - 220 c . f . s .

A ir m a s s ,

= 0 .0 0 2 5 8 (2 2 0 ) z 0 .4 7 6 s l u g s / s e c .

Momentum,

-|m (aV )S

Assume a 50% s a f e t y f a c t o r .

a V - 88 - 4 4 z 44 f . p . s . E n e rg y = 1 . 5 ( i ) 0 . 4 7 6 ( 4 4 ) 2 = 6 9 0 .5 f t . l b s . / s e c . 2 H .P . r e q . a t 100% e f f i c i e n c y , 6 9 0 .5 /5 5 0 = 1 .2 6 h . p . M o to r p o w er r e q u i r e d = 1 . 2 6 / ( 0 . 7 4 ) 0 . 8 5 z 2 h . p . a p p ro x . A tw o h o rs e p o w e r m o to r w as s e l e c t e d fro m c a t a l o g i n ­ fo rm a tio n .

M a n u f a c tu re d b y t h e K im ble E l e c t r i c Company, t h e

m o to r w as i n t e n d e d f o r u s e w i t h a s p e e d c o n t r o l t r a n s f o r m e r

23 a n d h a d t h e f o l l o w i n g n a m e - p la t e d a t a , 2 h . p . a t 1 ,8 0 0 rpm .

V a r i a b l e s p e e d 9 0 0 - 1 ,8 0 0 rpm .

220 v o l t s , 60 c y c l e , s i n g l e p h a s e c u r r e n t . The c h o ic e o f a f a n w as n e x t i n o r d e r .

A s ix -b la d e d

f a n w as c h o s e n s i n c e i t h a d a l r e a d y b e e n d e c id e d t o u s e f i v e c o n tr a v a n e s t o s u p p o r t t h e m o to r f a i r i n g .

The d i s c r e p a n c y

i n n um ber b e tw e e n t h e s e tw o i te m s w as d e l i b e r a t e l y c h o se n i n o r d e r to p re v e n t bad v i b r a t i o n a l e f f e c t s .

The d e s ig n c a l ­

c u l a t i o n s f o r t h e f a n w e re s t a r t e d b u t w e re n e v e r f i n i s h e d . The r e a s o n f o r t h i s w as t h a t a c a t a l o g came t o h a n d i n w h ic h a s u i t a b l e f a n w as l i s t e d .

T h i s w as a s i x - b l a d e d H a r t z e l l

m in e f a n o f t h i r t y - s i x in c h d i a m e t e r .

The c h o ic e o f t h i s

f a n e l i m i n a t e d t h e n e c e s s i t y f o r c o m p le tin g t h e f a n d e s i g n c a lc u la tio n s .

F u r t h e r , t h e f a n w o u ld c a r r y t h e m anu­

f a c t u r e r ’ s g u a r a n t e e , w o u ld b e c h e a p e r t o p u r c h a s e b e c a u s e of its

s t a n d a r d d e s i g n , a n d i t w o u ld be a s im p le m a t t e r t o

r e d u c e t h e l e n g t h o f e a c h b l a d e b y tw o i n c h e s t o make i t f i t th e s e le c te d d ia m e te r.

Two h u b s w e re a v a i l a b l e w i t h t h i s

f a n , o n e f o r s i x b l a d e s , an d on e f o r tw e lv e b l a d e s .

The

t w e l v e - b l a d e h u b w as c h o s e n s i n c e i t w o u ld be p o s s i b l e t o u s e e i t h e r s i x , f o u r , t h r e e , o r tw o b l a d e s w i t h i t i f f u t u r e t e s t s i n d i c a t e d s u c h t o be d e s i r a b l e . The f a n d e s i g n c a l c u l a t i o n s w h ic h w ere s t a r t e d h a v e n o t b e e n i n c o r p o r a t e d i n t o t h i s r e p o r t s i n c e t h e y now h a v e no s i g n i f i c a n c e .

84 III.

TORQUE BALANCE DESIGN

The d e s i g n o f t h e m o to r i n s t a l l a t i o n i n c l u d e d a t o r q u e arm t o be a t t a c h e d t o t h e m o to r f ra m e , t h e fra m e b e in g m o u n ted on b a l l b e a r i n g s so t h a t i t

c o u ld r o t a t e .

T h u s a d y nam om eter w as c r e a t e d b y w h ic h t h e o u t p u t h o r s e ­ p o w er o f t h e m o to r c o u ld b e o b t a i n e d .

The l e n g t h o f t h e

t o r q u e arm t u r n e d o u t t o b e 1 8 j| i n c h e s . To c a r e f o r a n y p o s s i b l e c h a n g e s w h ic h m ig h t b e i n ­ t r o d u c e d i n t h e f u t u r e , t h e maximum t o r q u e f o r c e w as c a l ­ c u l a t e d on t h e b a s i s o f t h r e e h o r s e p o w e r m o to r o u t p u t a t 900 rpm .

T h u s,

3 I 2lTFKN/33,000 o r,

F Z 3 ( 3 3 ,0 0 0 ) / 8 T r ( i ||2 5 ) 9 0 0 z 1 1 .2 l b s .

T h u s t h e t o r q u e b a la n c e s c a l e w as r e q u i r e d t o h a n d le a m a x i­ mum l o a d o f 1 1 .2 p o u n d s . D u rin g t h e c o u r s e o f c o n s t r u c t i o n o f t h e w i n d - t u n n e l p r o p e r a s t r o k e o f l u c k b r o u g h t t o h a n d t h e beam an d beam fra m e o f a C h a t i l l o n C o u n tin g S c a l e .

T h is u n i t p ro v e d t o b e

s u i t a b l e f o r u se a s th e to rq u e b a la n c e .

T h e re w as no q u e s ­

t i o n a s t o i t s b e in g a b l e t o h a n d le t h e maximum f o r c e o f 1 1 .2 p o u n d s .

I t w as n e c e s s a r y t o d e s i g n t h e beam p o i s e an d

t h e p a n w e i g h ts f o r u s e on t h e b a l a n c e .

G r a d u a tio n s o n t h e

beam c o n s i s t e d o f tw e n ty m a jo r d i v i s i o n s e a c h o f w h ic h w ere s u b d iv id e d i n t o e i g h t m in o r d i v i s i o n s .

T h e re fo re , th e

25 d e c i s i o n w as m ade t o u s e m a jo r d i v i s i o n s a s o u n c e s a n d m in o r d iv is io n s a s e ig h th s o f an o u n ce.

The d e s i g n c a l c u l a t i o n s

a r e shown b e lo w . 21.188 12.75 20

C o u n te r B a la n c e

Wg- W eig h t o f Beam

K = T a re W eig h t (assu m e z e r o )

F = T o rq u e F o rc e (1 2 l b . m a x .)

P z

A c tu a l P an W eig h t

B = W eig h t o f R i d e r P o i s e

A.

F

=

0,

P =

0,

Wxb = WgX 4 2 .6 2 5 B B.

F= l l b . ,

P = 0,

B a t in d e x

+ 1 .2 5 7 = % X 4 B [2 .6 2 5

16

4# ( 1 2 .7 5 ) ]

W2X 4 2 .6 2 5 B 4 1 .2 5 1 = WgX 4 2 .6 2 5 B 4 1 0 . 2B 1 .2 5 ( 1 ) = 1 0 . 2B B = 1 . 2 5 / 1 0 . 2 = 0 .1 2 2 5 l b . C.

I :

lib.,

B i s a t z e r o in d e x

Wjb 4 1 .2 5 7 = WgX 4 2 .6 2 5 B 4 2 1 .1 8 8 P W2X 4 2 .6 2 5 B 4 1 .2 5 ( 1 ) = W2X 4 2 .6 2 5 B 4 2 1 .1 8 8 P 1 .2 5 ( 1 ) = 2 1 .1 8 8 P P = 1 .2 5 / 2 1 .1 8 8 = 0 .0 5 9 1 l b .

26 D.

F o r F = 12 l b . ,

P = 1 2 ( 0 .0 5 9 1 ) = 0 .7 0 8 l b .

The d e s i g n c a l c u l a t i o n s show t h a t t h e a c t u a l w e ig h t o f t h e beam r i d e r s h o u ld b e 0 .1 2 2 5 p o u n d , a n d t h a t o f a o n e -p o u n d p a n w e ig h t s h o u ld b e 0 .0 5 9 1 p o u n d .

The p a n w e i g h ts

w e re made o f o n e - e i g h t h i n c h d u r a lu m in s h e e t .

A t o t a l o f s ix

w e i g h ts w e re m ad e, tw o w e i g h ts e a c h in d e x e d a s 16 o u n c e s , t h r e e in d e x e d a s 52 o u n c e s e a c h , a n d one in d e x e d a s 80 ounces.

The 1 6 -o u n c e w e i g h ts w e re s i n g l e d i s c s .

The o t h e r s

w e re made up o f two d i s c s e a c h f o r t h e 3 2 -o u n c e w e i g h t s , and f i v e d i s c s f o r t h e 8 0 -o u n c e w e i g h t . u s e d t o h o ld t h e d i s c s t o g e t h e r .

Aluminum r i v e t s w e re

S in c e alum inum w e ig h s

0 .0 9 7 8 5 p o u n d p e r c u . i n . t h e a p p r o x im a te d i s c d i a m e t e r s w e re fo u n d t o b e , ^ ( ^ ) d 8 = 0 .0 5 9 1 /0 .0 9 7 8 5 d2 = 3 2 ( 0 1 0 5 9 1 ) r r ' 0 . 09785 d = 2 .4 8 i n c h e s S in c e e a c h d i s c w as t o h a v e one s l o t o f t h r e e s i x t e e n t h i n c h w id th r u n n in g i n t o t h e c e n t e r , a d i a m e t e r o f tw o an d s e v e n - t e n t h s i n c h e s w as u s e d .

The d i s c s w e re a d ­

j u s t e d i n w e ig h t b y d r i l l i n g h o l e s i n th e m w h i l e c h e c k in g a g a in s t dead w e ig h ts .

The o p e r a t i o n w as p e rf o r m e d u s i n g t h e

t o r q u e beam f o r t h e b a l a n c i n g . The beam r i d e r w as made w i t h a n alum inum b o d y an d a s te e l s lin g .

The w e ig h t o f t h e s t e e l w as 0 .0 3 9 6 pound an d

27 t h a t o f t h e alum inum w as 0 .0 8 2 8 pound i n d i c a t e d .

T hus t h e

alum inum p i e c e w as one a n d o n e - e i g h t h inG h i n d i a m e t e r an d s l i g h t l y o v e r n i n e - t e n t h s o f an in c h lo n g .

The w e ig h t o f

t h e r i d e r w as a d j u s t e d i n t h e same m an n e r a s t h a t o f t h e p a n w e ig h ts . XV.

SPHERE DRAG BALANCE

The s p h e r e d r a g t e s t i n v o l v e s t h e u s e o f a s p e c i a l b a la n c e a n d s u p p o r t s y s te m d i s t i n c t fro m t h e g e n e r a l s e r v i c e b a l a n c e s y s te m o f t h e t u n n e l .

I t w as e x p e d i e n t t o b u i l d

t h i s s p e c i a l b a la n c e b e c a u s e o f t h e m eth o d b y w h ic h t h e s p h e r e m u st be s u p p o r t e d , a n d b e c a u s e o f t h e d e s i r e t o m e a s u re p r e s s u r e d i f f e r e n c e s a c r o s s t h e s p h e r e a s w e l l a s th e a c t u a l d rag f o r c e a p p lie d to i t .

F u r t h e r d i s c u s s i o n on

t h i s p o i n t i s p r e s e n t e d i n C h a p te r V. T he maximum v a lu e o f d r a g f o r c e t o be m e a s u re d w as e s t i m a t e d b y c o n s i d e r i n g t h e maximum d e s i g n v e l o c i t y o f t h e tu n n e l and th e d ia m e te r o f th e l a r g e s t sp h e re t o be u s e d . T h u s, Vmax = 8 8

“ 4 V ax = 4 i n ‘

C o n s id e r in g s t a n d a r d a i r c o n d i t i o n s , R e y n o ld s Number = ^ or

N.H. = 6 3 8 0 ( 8 8 ) i = 1 8 7 , 0 0 0

28 T h us,

CD = 0 .3 5 a p p ro x .

The s p h e r e d r a g i s t h e n , D - Cjji^AV2 w h e re A = ^ d 2 T h u s,

D = 0 .3 5 ( 0 .0 0 1 1 9 ) 5 l | ) ( 8 8 ) 8 = 0 .2 8 2 l b .

S in c e t h e d r a g o f t h e s u p p o r t s t r u t w i l l a l s o r e g i s t e r on t h e b a la n c e a llo w a n c e w as m ade f o r i t .

T h is a llo w a n c e w as

t a k e n a s 50 p e r c e n t o f t h e maximum s p h e r e d r a g .

Thus th e

t o t a l maximum f o r c e t o be m e a s u re d b y t h e d r a g b a la n c e w a s, F r 1 .5 ( 0 .2 8 2 ) = 0 .4 2 3 l b . I n v ie w o f t h i s t h e b a la n c e w as d e s ig n e d t o m e a su re f o r c e s fro m z e r o t o o n e - h a l f p o u n d .

The f o r c e d ia g ra m f o r t h e

s p h e r e d r a g b a la n c e beam i s shown b e lo w .

in

---- > PQ

1

*------------- 1 0 f i ---------------------- » ------------ X ------ > 1*2.375-* 1 0.0 0.

ii

- — V W

2 115” .

W-^ = C o u n te r W e ig h t D = S p h e re D rag

Wg = W e ig h t o f Beam B = W eig h t o f Beam R id e r

1 R. C. B i n d e r , F l u i d M e c h a n ic s ( s e c o n d e d i t i o n ; New Y ork: P r e n t i c e - H a l l , I n c . , 194:9), p . 1 7 3 .

29 A.

D = 0 Wxb

B.

I

W2X

4

2 .3 7 5 B

D = 0 .5 l b . Wxb

4

o r,

15D = WgX

4

( 2 .3 7 5

4

10)B

WgX 4 2 .3 7 5 B 4 15D = WgX 4 2 .3 7 5 B 4 10B

T h u s,

15 D = 10B B = ( 1 |) ( 0 .5 )

= 0 .7 5 l b .

T h u s t h e a c t u a l w e ig h t o f t h e beam r i d e r i s 0 .7 5 p o u n d . The beam r i d e r w as c o n s t r u c t e d o f a b r a s s b o d y s u p p o rte d by a s t e e l s l i n g .

The w e ig h t o f t h e s l i n g w as

fo u n d t o b e 0 .0 3 1 2 pound a f t e r c o n s t r u c t i o n .

T hus t h e

w e ig h t o f b r a s s r e q u i r e d w as 0 .7 5 - 0 .0 3 1 2 r 0 .7 1 8 8 l b . B r a s s r o d o f o n e an d o n e - q u a r t e r i n c h d i a m e t e r w as u s e d an d s i n c e t h e w e ig h t o f b r a s s i s a p p r o x i m a t e ly 0 .3 0 6 p o u n d p e r c u . i n . t h e le n g th r e q u ir e d w as, ( ? ) d s L ( 0 .3 0 6 ) = 0 .7 1 8 8

L=

2 = 1*913 laches

The b r a s s b o d y w as made tw o i n c h e s l o n g .

A f t e r a s s e m b ly ,

t h e r i d e r w as c a r e f u l l y a d j u s t e d t o a w e ig h t o f 0 .7 5 p o u n d .

30 V.

LIST AND DRAG BEAMS OF THE TUNNEL BALANCE SYSTEM

The l e n g t h s o f t h e l i f t a n d d r a g beam s w ere made e q u a l and w e re g o v e rn e d b y t h e s p a c e a v a i l a b l e f o r m o u n tin g t h e b a la n c e s y s te m .

To s i m p l i f y c o n s t r u c t i o n , a l l c o n ­

s t r u c t i o n a l d e t a i l s w e re i d e n t i c a l on t h e tw o t y p e s o f beam s in c lu d in g th e in d e x l i n e s .

H ow ever, t h e m ark e d in d e x v a l u e s

on t h e d ra g beam s w e re made t o be h a l f t h o s e on t h e l i f t b e am s.

The l e n g t h o f t h e in d e x e d s c a l e w as made t o be f i v e

a n d o n e - h a l f i n c h e s i n e a c h e a s e , t h e en d in d e x b e in g m ark e d a s 0 .5 5 p o u n d on t h e l i f t b e am s. The a c t u a l w e i g h ts o f t h e beam r i d e r s a n d p an w e i g h t s w e re fo u n d i n t h e f o l l o w i n g m a n n e r. L i f t B eam s. 8 .7 5 ”

> I

it B

*w

i 0 .5 5

2 .1 2 5 ”Xk - i.o ^ -----------1-------T ffrr 0 .0 \

32; « to

• 5 .5 ”

1r l Wj z C o u n te r W eig h t

t L

Wg = W e ig h t o f Beam

K = T a re W eig h t {assum e z e r o )

L z L i f t F o rc e (u pw ard)

P z P an W eight

B = W e ig h t o f R i d e r

31 A.

L z 0,

P =: 0

Wj b r W2X 4 2 . 1255 B.

L = 0.55 l b . ,

P = 0

W-jb z WgX - L(1) 4 B ( 2 . 1 2 5 4 5 . 5 ) WgX 4 2 .1 2 5 B = W2X - L(1 ) 4 2 . 1 2 5 B 4 5 .5 B 5 .5 B z L B = C.

L z 0 .5 0 l b . ,

= 0 . 5 5 / 5 . 5 Z 0 .1 l b P > ^0 ,

W-jb Z WgX - L ( l )

4

B a t z e ro In d e x .

2 .1 2 5 B

WgX 4 2 .1 2 5 B z W2X - L (1 )

4 8 .7 5 P 4

2 .1 2 5 B 4 8 .7 5 P

8 .7 5 P Z L P Z L /8 .7 5 = 0 . 5 / 8 . 7 5 z 0 .0 5 7 1 5 l b . T h u s f o r e a c h l i f t beam a r i d e r o f o n e - t e n t h po u n d t r u e w e ig h t w as r e q u i r e d , a n d p a n w e i g h ts o f 0 .0 5 7 1 5 pound w e re r e q u i r e d f o r e a c h h a l f pou n d in c r e m e n t i n l i f t . D rag B eam s. 7 .7 5 -6 .6 2 5

0.0

0 .2 7 5 B

W, 2

W. 1

32 - C o u n te r W eig h t K = T a r e W e ig h t

W = W eig h t o f Beam (a ssu m e z e r o )

P = P a n W eig h t A.

D r 0,

D r D rag flo rc e B = W eig h t o f H id e r

P = 0

Wjb = WgX + 1 .1 2 5 B B.

D r 0 .2 7 5 l b . , W.b t

P r 0

D (l) = WgX + 6 .6 2 5 B

W X ♦ 1 .1 2 5 B + D ( l) = W2X ♦

1 .1 2 5 B + 5 .5 B

D (l) : 5 .5 B B : D /5.5 r 0 .2 7 5 /5 .5 r 0.05 l b . C.

D r 0 .2 5 0 l b . , P ^ O ,

B a t z e ro in d e x .

Wxb •* D ( l ) r WgX -t 1 . 1 2 5 B + WgX + 1 .1 2 5 B + D ( l) r WgX +

7.75P 1 .1 2 5 B ■»7 .7 5 P

7.75P r D (l) P r D /7 .7 5 r 0 . 2 5 / 7 . 7 5 r 0 .0 3 2 2 5 T h u s t h e d r a g beam s

e a c h r e q u i r e a r i d e r o f 0 .0 5

lb .

pou n d t r u e

w e i g h t , a n d p a n w e i g h t s o f 0 .0 3 2 2 5 pou n d t r u e w e ig h t f o r e a c h 0 .2 5 0 pound in c r e m e n t i n d r a g .

CHAPTER IV METHODS AND PROBLEMS OP CONSTRUCTION I n g e n e r a l , t h e m e th o d s and p ro b le m s o f c o n s t r u c t i o n o f th e w in d -tu n n e l and i t s

a c c e s s o r i e s w e re s im p le .

Pew

u n u s u a l f e a t u r e s w e re e n c o u n t e r e d . I .

WOODEN CONSTRUCTION

The i n i t i a l c o n s t r u c t i o n w ork c o n s i s t e d o f b u i l d i n g t h e b a s e f r a m e , F i g u r e I E , an d o f c u t t i n g o u t t h e p ly w o o d p a n e l s , F ig u r e 1 1 .

The p a n e l fra m in g w as c u t t o s i z e an d

f i t t e d to th e in d iv id u a l p a n e ls . w e re t h e n p u t t o g e t h e r .

S u b a s s e m b le s o f p a n e l s

The h ig h p r e s s u r e e n d o f t h e t u n n e l

w as t h e n a s s e m b le d t o t h e b a s e f r a m e , o m i t t i n g t h e s e t t l i n g c h a m b e r.

The s h e e t - m e t a l f a n s e c t i o n w as s e t i n p l a c e te m ­

p o r a r i l y , an d t h e low p r e s s u r e e n d o f t h e t u n n e l w as a s s e m b le d t o t h e b a s e fra m e o m i t t i n g t h e d i f f u s e r s e c t i o n . The f a n s e c t i o n w as t h e n rem oved an d t h e t u r n i n g v a n e s w e re i n s t a l l e d i n t h e lo w e r c o r n e r s .

T h e s e v a n e s a r e s im p ly

s h e e t - m e t a l q u a d r a n t s o f c i r c u l a r c y l i n d e r s an d a r e r i g i d l y a tta c h e d to th e tu n n e l w a lls . H o r i z o n t a l a lig n m e n t o f t h e e n d s e c t i o n s a l r e a d y m e n tio n e d w as d e p e n d e n t upon t h e a c c u r a c y w i t h w h ic h t h e b a s e fra m e w as c o n s t r u c t e d .

V e r t i c a l a lig n m e n t w as o b t a i n e d

w i t h t h e a i d o f t h e f a n s e c t i o n an d m e a s u re m e n ts t a k e n fro m

34 a f a i r l y f l a t s e c tio n o f th e la b o r a to r y flo o r* H a v in g i n s t a l l e d t h e lo w e r t u r n i n g v a n e s , te m p o r a r y u p r i g h t s w ere cla m p e d t o t h e s t r u c t u r e f o r t h e p u r p o s e o f s u p p o r t i n g t h e s e t t l i n g c h am b er a n d t h e d i f f u s e r d u r i n g t h e i r a s s e m b ly -

T h e se u n i t s w e re k n o c k e d down i n t o t h e i r

co m ponent p a r t s .

T h e i r s i d e w a l l s w e re t h e n a s s e m b le d t o

t h e t u n n e l , a lig n m e n t b e in g a t t a i n e d w i t h t h e a i d o f s tre tc h e d s tr in g s .

M is a lig n m e n t o f t h e c o n t a c t s u r f a c e s

d u r i n g t h i s o p e r a t i o n d i d n o t e x c e e d o n e t h i r t y - s e c o n d o f an in c h .

The t o p a n d b o tto m w a l l s o f t h e s e s e c t i o n s w e re t h e n

r e a s s e m b le d t o t h e s i d e w a l l s , a n d t h e p e rm a n e n t s u p p o r t s a t t h e t h r o a t w e re i n s t a l l e d .

The t u r n i n g v a n e s i n t h e u p p e r

c o m e r s w e re t h e n a s s e m b le d , a n d t h e v e r t i c a l p a n e l a t t h e h i g h p r e s s u r e en d o f t h e t u n n e l w as s e c u r e d i n p l a c e . No n a i l s w e re u s e d i n a n y o f t h e a s s e m b ly . w e re s e c u r e d b y m eans o f wood s c re w s o r b o l t s .

A ll p a r t s

C a rria g e

b o l t s w e re u s e d i n t h e b a s e f r a m e . II.

THE PAN SECTION

The p h o t o g r a p h s , F i g u r e s 1 t o 8 , a n d t h e d ra w in g , F ig u r e 1 3 , show t h e s h e e t - m e t a l f a n s e c t i o n . s e c t i o n w as made o f s i x p i e c e s .

The t r a n s i t i o n

T h re e o f t h e s e w e re

a s s e m b le d i n t o a u n i t b y s p o t w e l d in g , a n d t h i s u n i t fo rm s t h e lo w e r h a l f o f t h e f a n s e c t i o n .

The u p p e r h a l f w as l e f t

a s t h r e e d i s t i n c t p i e c e s f o r p u r p o s e s o f m o to r an d f a n

35 a c c e s s ib ility .

T h is s h e e t - m e t a l w o rk w as done b y a l o c a l

s h e e t-m e ta l sh o p . T h is f a n s e c t i o n w as a s s e m b le d i n t h e t u n n e l an d w as s e c u r e d o n l y a t t h e e n d s w h e re i t

j o i n s t h e wooden d u c t .

Long b o l t s w e re u s e d f o r t h i s p u r p o s e , a n d a lig n m e n t o f t h i s s e c t i o n h a d a l r e a d y b e e n a s s u r e d b y t h e m eth o d u s e d i n a s s e m b lin g t h e w ooden p a r t s . X II.

THE MOTOR AND IT S SUPPORT

D e t a i l s o f t h e m o to r s u p p o r t s y s te m m ay be s e e n i n F i g u r e s 16 t o 1 9 .

The fra m e w as f a b r i c a t e d fro m a n g le i r o n ,

w i t h a l l b u t tw o m em bers b e i n g w e ld e d i n p l a c e .

The tw o

f o r e - a n d - a f t d i a g o n a l b r a c e s w e re b o l t e d t o t h e m a in fr a m e , a n d t h e w h o le u n i t w as t h e n b o l t e d t o tw o c r o s s m em bers w h ic h w e re t o a c t a s a b e d p l a t e .

A tta c h m e n t t o t h e b a s e

fra m e w as t o be th r o u g h t h e s e c r o s s m em b ers.

S in c e t h e s e

c r o s s m em bers w e re t o be o u t s i d e o f , an d b e lo w , t h e f a n s e c t i o n i t w as n e c e s s a r y t o h a v e t h e l e g s o f t h e fra m e p a s s th r o u g h t h e w a l l o f t h e f a n s e c t i o n .

I t w as p o s s i b l e t o

a c h i e v e a s s e m b ly i n t h i s fo rm i n e i t h e r o f tw o w a y s.

L a rg e

h o l e s c o u ld be c u t i n t h e w a l l so t h a t t h e l e g s c o u ld be w o rk ed t h r o u g h w i t h t h e fra m e a s a u n i t , o r , tw o o f t h e l e g s c o u ld b e c u t t h e r e b y a ll o w i n g t h e u s e o f s m a ll h o l e s in th e w a ll.

The l a t t e r m eth o d w as c h o s e n b e c a u s e i t w o u ld

c a u s e a minimum o f d i s t u r b a n c e o f t h e a i r f lo w a n d w o u ld

36 n o t g r e a tly a f f e c t th e r i g i d i t y o f th e fan s e c tio n .

S h o rt

p i e c e s o f a n g le i r o n w ere n e s t e d i n t o t h e tw o l e g s o f one s i d e o f t h e f r a m e , a n d e i g h t h o l t s w e re i n s t a l l e d i n e a c h . T h e se p i e c e s w e re t h e n rem oved a n d t h e l e g s w e re c u t .

On

r e a s s e m b l y , t h e a lig n m e n t w as fo u n d t o be a s b e f o r e . The m o to r w as t h e n m o u n te d on t h e f r a m e , t h e b e a r i n g s u p p o r t s a n d j o u r n a l s h a v in g b e e n p r e v i o u s l y m a c h in e d .

The

d i r e c t s u p p o r t o f t h e m o to r w as a t t a i n e d t h r o u g h f o u r b a l l b e a r i n g s , on e a t t h e r e a r a n d t h r e e a t t h e f a n e n d . p a r t s in v o lv e d a r e shown i n F i g u r e s 17 a n d 1 8 .

The

The f a n

t h r u s t i s c a r r i e d th r o u g h t h e m o to r s h a f t a n d i t s b e a r i n g s t o t h e m o to r f r a m e .

The fra m e t h e n t r a n s m i t s t h e l o a d t o

t h e r e a r s u p p o r t j o u r n a l fro m w h ic h i t i s ta k e n t o t h e m o to r s u p p o r t fra m e t h r o u g h t h e r e a r b e a r i n g .

The t h r e e

f r o n t b e a r i n g s c a r r y o n l y r a d i a l l o a d s , an d t h e t o p b e a r i n g o f th e s e th r e e i s a d ju s ta b le in a r a d i a l d ir e c tio n .

H ig h

s t r e n g t h a i r c r a f t p a r t s w e re u s e d h e r e t o c o m p e n sa te f o r t h e s m a ll s i z e s r e q u i r e d . H a v in g a c h i e v e d a s s e m b ly a n d a lig n m e n t o f t h e m o to r in i t s

fra m e t h e p a r t s w e re d is a s s e m b le d p r e p a r a t o r y t o

i n s t a l l a t i o n in th e tu n n e l.

To a c h ie v e t h i s s t a g e o f

a s s e m b ly h o l e s w e re l a i d o u t a n d c u t i n t h e w a l l o f t h e f a n s e c tio n .

The c r o s s m em bers o f t h e m o to r s u p p o r t fra m e w e re

t h e n c la m p e d t o t h e w ooden b a s e fra m e and t h e m o to r s u p p o r t fra m e w as p l a c e d i n t h e t u n n e l .

A p p ro x im ate a lig n m e n t w as

37 o b t a i n e d a n d t h e m o to r w as r e a s s e m b le d t o t h e s u p p o r t f r a m e . The a lig n m e n t w as c h e c k e d a g a i n an d t h e f a n w as t h e n p l a c e d on t h e m o to r s h a f t .

W ith t h e f a n i n p o s i t i o n t h e a lig n m e n t

w as a d j u s t e d a n d b o l t s w e re t h e n i n s t a l l e d i n t h e w ooden b a s e fra m e t o h o ld t h e c r o s s m em bers o f t h e m o to r f r a m e . The f a n w as t h e n rem oved a n d t h e f i n a l s e c u r i n g o f t h e m o to r w as a c h i e v e d . IV .

MOTOR FAIRING, AFTER-BODY, AND STRAIGHTENING VANES

D e t a i l s o f t h e s e u n i t s may b e fo u n d i n F ig u r e 2 6 . The f a i r i n g p r o p e r c o n s i s t e d o f s e v e r a l s h e e t s o f alum inum w h ic h w ere w ra p p e d a ro u n d t h e m o to r a n d i t s

s u p p o r t f ra m e .

T he m a in s h e e t e x te n d e d fro m t h e f a n s e c t i o n w a l l a lo n g t h e l e g s o f t h e m o to r s u p p o r t , a ro u n d an d o v e r t h e m o to r , and down t h e l e g s on t h e o t h e r s i d e o f t h e s u p p o r t , t o t h e w a l l . T h re e s h e e t s w e re u s e d on t h e u n d e r s i d e o f t h e s u p p o r t t o e n c l o s e i t an d t h e m o to r .

Two o t h e r s h e e t s w e re w ra p p e d

a ro u n d t h e f r o n t l e g s n e a r t h e f a n , a n d tw o s h e e t s e a c h w ere r i v e t e d to g e th e r and e n c lo s e d th e r e a r le g s o f th e s u p p o rt. A c r o s s s e c t i o n o f t h e f a i r i n g a ro u n d t h e l e g s o f t h e m o to r s u p p o r t w as m ade t o h a v e t h e g e n e r a l a p p e a ra n c e o f a n a i r ­ f o i l o f c o n s t a n t t h i c k n e s s o v e r m o st o f i t s T he t r a i l i n g

ed g e o f t h i s

c o n to u r o f t h e a f t e r - b o d y .

c h o rd l e n g t h .

s e c t i o n w as e x te n d e d t o m a tc h t h e A ll o f t h e s h e e t alum inum

38 m e n tio n e d so f a r w as a t t a c h e d t o t h e m o to r s u p p o r t f r a m e . A o n e - i n c h c l e a r a n c e w as m a i n t a i n e d b e tw e e n t h e s h e e t and t h e m o to r f r a m e .

A s h i e l d i n g w as i n s t a l l e d a t t h e f a n e n d

o f t h e f a i r i n g t o p r e v e n t t h e a i r fro m b l a s t i n g i n t o t h e fa irin g .

T h is e n t i r e a s s e m b ly w as a c h ie v e d b y t h e c u t - a n d -

t r y m e th o d an d no e x t e n s i v e d e t a i l s a r e shown f o r i t on a n y d r a w in g . H a v in g i n s t a l l e d t h e f a i r i n g , t h e a f t e r - b o d y w as t h e n c o n s t r u c t e d t o m a tc h .

The m e th o d u s e d w as t o c o n s t r u c t a

r i n g o f s h e e t alum inum w h ic h w as f i t t e d t o t h e i n s i d e o f t h e fa irin g .

E l a s t i c s t o p - n u t s w e re a t t a c h e d t o t h e i n s i d e o f

t h i s r i n g a f t e r d r i l l i n g b o l t h o l e s i n t h e f a i r i n g an d r i n g . A w ooden b o d y o f r e v o l u t i o n w as t h e n made su c h t h a t t h e r i n g w o u ld f i t

s n u g ly o v e r i t s b a s e .

Common w indow s c r e e n i n g w as

t h e n draw n t i g h t l y down o v e r t h e wood an d w as r i v e t e d t o t h e sh e e t-m e ta l r in g .

The m e t a l a s s e m b ly w as t h e n rem oved fro m

t h e w ood, a n d t h e s u r f a c e o f t h e wood w as c o v e r e d w i t h s h e e t s o f wax p a p e r . fo rm .

The m e t a l w as t h e n r e p l a c e d on t h e

W a t e r - p u t t y w as a p p l i e d t o t h e s c r e e n i n g t o b u i l d up

a sm o oth c o n ti n u o u s s u r f a c e .

A f t e r d r y i n g , t h i s s u r f a c e w as

p a i n t e d , an d t h e wooden fo rm w as rem o v e d .

T h is same p r o ­

c e d u r e w as u s e d i n t h e c o n s t r u c t i o n o f t h e s p i n n e r f o r t h e fan . I n s t a l l a t i o n o f t h e a f t e r - b o d y a lo n g w i t h t h e b a f f l e s h e e t a t t h e f a n e n d p r o v id e d c o n s i d e r a b l e r i g i d i t y t o t h e

fa irin g .

T h is w as i n c r e a s e d b y t h e i n s t a l l a t i o n o f t h r e e

s tra ig h te n in g v an es.

T h e se v a n e s w e re a l s o m ade o f s h e e t

alu m in u m , t h e s h e e t b e in g fo rm ed i n t o a c o n v e n ie n t a i r f o i l s e c tio n .

Two o f t h e s e w e re i n s t a l l e d on t h e h o r i z o n t a l

r a d ii o f th e fan s e c tio n .

The t h i r d w as m o u n te d ab o v e t h e

m o to r on t h e v e r t i c a l r a d i u s .

A ll t h r e e w e re s e t a t an

a n g le su c h a s t o p a r t i a l l y rem ove t h e r o t a t i o n a l v e l o c i t y w h ic h a f a n i m p a r t s t o t h e a i r i t m o v e s.

I t i s in te n d e d

t h a t a d j u s t m e n t s t o t h e s e v a n e s , an d t o t h e t r a i l i n g e d g e s o f t h e f a i r i n g be made so a s t o rem ove t h e r o t a t i o n a l e ffe c ts e n tire ly .

T h e s e a d ju s tm e n t s w i l l d e p e n d upon t e s t s

o f t h e a i r f lo w i n t h e t u n n e l t h r o a t . The t h r e e v a n e s w e re a t t a c h e d t o t h e f a i r i n g and t o th e w a ll o f th e fa n s e c tio n . f o r th e f a i r i n g .

T h ey t h e r e b y p r o v i d e s u p p o r t

H o le s w e re c u t i n t h e f a i r i n g t o p r o v i d e

an a i r p a s s a g e fro m t h e m o to r i n t o t h e u p p e r s t r a i g h t e n i n g vane.

M a tc h in g h o l e s w e re c u t i n t h e w a l l o f t h e f a n

s e c t i o n t o p r o v i d e an o u t l e t f o r t h e a i r .

T h is a i r p a s s a g e

w as p r o v i d e d so a s t o d i s c a r d t h e m o to r c o o l i n g a i r an d t h e r e b y m a i n t a i n a m ore u n i f o m t h r o a t a i r t e m p e r a t u r e a t a l l o p e ra tin g c o n d itio n s .

A ir i s v e n te d t o t h e m o to r

t h r o u g h t h e u n s e a l e d j o i n t s o f t h e f a i r i n g an d th r o u g h an o p e n in g i n t h e l e a d i n g e d g e o f one o f t h e h o r i z o n t a l v a n e s . A m a tc h in g h o l e w as p r o v id e d i n t h e f a i r i n g f o r t h i s i n l e t

40 On t h e o t h e r s i d e o f t h e m o to r a h o l e w as c u t i n t h e f a i r i n g f o r t h e t o r q u e a rm .

T h is a n a c o n s i s t s o f a d u ra lu m in

t u b e th r o u g h w h ic h t h e p o w er l e a d s r e a c h t h e m o to r .

The

t o r q u e a n a e x te n d s fro m t h e m o to r t o o u t s i d e t h e f a n s e c t i o n , p a s s i n g t h r o u g h one o f t h e h o r i z o n t a l s t r a i g h t e n i n g v a n e s . The p h o t o g r a p h s , F i g u r e s 1 t o 8 , a n d F ig u r e 2 7 , show d e t a i l s o f t h e f a i r i n g an d t o r q u e arm . V.

THE FAN AND IT S SPINNER

As s t a t e d on F i g u r e 2 0 , t h e f a n w as m ade b y H a r t z e l l P r o p e l l e r F an Co.

I t i s a s i x - b l a d e d u n i t w h ic h h a s b e e n

r e d u c e d i n d i a m e t e r fro m t h i r t y - s i x i n c h e s t o t h i r t y - t w o in c h e s.

I t i s m o u n te d i n a t w e l v e - b l a d e h u b , an d t h e num ber

o f b l a d e s i n u se c a n be a l t e r e d i f t h a t s h o u ld e v e r be d e ­ s ire d .

The f a n w as s u p p o s e d t o h a v e b e e n b a la n c e d b e f o r e i t

l e f t th e fa c to ry .

A s t a t i c b a la n c e t e s t show ed t h a t i t w as

u n b a la n c e d , a n d re m o v a l o f n e a r l y o n e t h i r t y - s e c o n d o f an i n c h o f m e t a l fro m t h e t i p

o f o n e b l a d e w as n e c e s s a r y t o

b a la n c e i t . The s p i n n e r w as c o n s t r u c t e d i n t h e same m a n n e r a s w as th e a fte r-b o d y .

S in c e t h e s p i n n e r w as t o be a t t a c h e d

d i r e c t l y to th e fa n , i t re q u ire d b a la n c in g .

T h is w as

a c h i e v e d b y f i r s t m ak in g a p l a t e t o a c t a s t h e f a n h u b , t o w h ic h t h e s p i n n e r w as a t t a c h e d . a o n e -in c h d r i l l ro d and i t s

T h is p l a t e w as m o u n te d o n

s t a t i c b a la n c e w as c h e c k e d .

41 The s p i n n e r w as t h e n m o u n te d on t h e p l a t e and w as b a la n c e d s t a t i c a l l y b y a d d in g s m a ll a m o u n ts o f w a t e r p u t t y t o t h e in s id e s u rfa c e .

The s p i n n e r w as t h e n a s s e m b le d t o t h e f a n ,

t h e f a n m o u n te d on t h e r o d , a n d t h e s t a t i c b a la n c e o f t h e u n i t w as c h e c k e d .

I n e a c h c a s e t h e w ays o f a l a t h e w e re

used a s th e p a r a l l e l s f o r b a la n c in g .

S ubsequent o p e ra tio n

o f t h e f a n i n t h e t u n n e l show ed t h a t t h e r e m a in in g u n ­ b a la n c e w as i n s u f f i c i e n t t o a c t u a t e t h e ffrahm v i b r a t i n g r e e d t a c h o m e t e r , a n d a n e x t r a n u t w as p l a c e d on t h e hub t o p r o ­ v i d e a d d i t i o n a l u n b a la n c e . I n m o u n tin g t h e f a n on t h e m o to r s h a f t , i t w as n e c e s ­ s a r y t o d r i l l a n d t a p t h e e n d o f t h e s h a f t so t h a t a s p e c i a l r e t a i n i n g s c re w c o u ld be u s e d t o p r o v i d e p o s i t i v e a t t a c h m e n t .

CHAPTER V INSTRUMENTS The u s e f u l n e s s o f a w i n d - t u n n e l i s d e te r m in e d l a r g e l y by th e in s tr u m e n ta tio n a v a i la b l e f o r u se w ith i t .

The

i n s t r u m e n t s i n v o lv e d i n t h e t e s t o f an a i r f o i l o r o t h e r ite m a r e c o m p a r a t i v e l y few i n n u m b e r.

H o w ev er, much o f t h e t e s t

d a t a d e p en d upon t h e c a l i b r a t i o n o f t h e t u n n e l w h ic h i n t u r n d e p e n d s upon i n s t r u m e n t s o f m ore o r l e s s s p e c i a l n a t u r e . In d e v is in g in s tru m e n ts f o r u se w ith t h i s tu n n e l th e b a s i c p u r p o s e o f t h e t u n n e l w as t h e f o r e m o s t c o n s i d e r a t i o n . I n t h i s c o n n e c ti o n c e r t a i n ite m s w e re d e v is e d w h ic h w o u ld n o t o r d i n a r i l y b e im m e d ia te ly a t h a n d f o r a t u n n e l n o t u s e d in in s tr u c tio n . The i n s t r u m e n t s w h ic h w ere d e v is e d f o r u s e w i t h t h e tu n n e l a re s p e c if ie d in th e fo llo w in g l i s t . 1.

S t a t i c - P l a t e M anom eter an d P r e s s u r e O p e n in g s .

2.

V a r i a b l e - s l o p e I n c l i n e d M a n o m eter.

3.

P i t o t - S t a t i c Tube ( P r a n d t l t y p e ) .

4.

F lo w - d ir e c tio n I n d i c a to r T ube.

5.

B o u n d a ry L a y e r P i t o t a n d S t a t i c T u b e s .

6.

D rag S p h e re s an d S p h e re D rag B a la n c e S y ste m .

7.

T o rq u e M e a s u rin g D e v ic e f o r d e te r m i n i n g t h e p o w er in p u t t o th e fa n .

8.

M odel B a la n c e a n d S u p p o rt S y ste m .

43 The i n s t r u m e n t s l i s t e d a b o v e w e re d e s ig n e d and c o n s tru c te d a s p a r t o f t h i s p r o je c t.

One i n s t r u m e n t w as

p u r c h a s e d , t h e Frahm V i b r a t i n g R eed T a c h o m e te r. I .

STATIC-PLATE MANOMETER AND PRESSURE OPENINGS A w e ll-k n o w n p r i n c i p l e o f F l u i d M e c h a n ic s s t a t e s t h a t

t h e s t a t i c p r e s s u r e i n a m oving f l u i d

s tr e a m i s d e p e n d e n t

upon t h e v e l o c i t y o f t h e s tr e a m a t t h e p o i n t w h e re t h e p r e s s u r e i s m ea su re d .

T h is p r i n c i p l e w as u t i l i z e d i n t h e

S t a t i c - P l a t e M a n o m e te r. C o p p er t u b e s w e re i n s t a l l e d

so t h a t t h e e n d o f one

t u b e w as f l u s h w i t h t h e i n n e r s u r f a c e o f t h e o v e rh e a d w a l l o f t h e s e t t l i n g c h a m b e r.

The e n d o f t h e o t h e r tu b e w as

i n s t a l l e d i n t h e same m an n e r w i t h i t s o p e n in g a t t h e t h r o a t o f th e tu n n e l. A m a n o m ete r t u b e w as i n s t a l l e d on t h e o u t e r w a l l o f th e tu n n e l a t a s lo p e o f 1 /1 5 .

The lo w e r e n d o f t h i s w as

c o n n e c te d t o t h e b o tto m o f a f o u r - i n c h d i a m e t e r r e s e r v o i r . The u p p e r e n d o f t h e m an o m ete r w as j o i n e d t o t h e c o p p e r tu b e le a d in g to th e tu n n e l t h r o a t .

The u p p e r p a r t o f t h e r e ­

s e r v o i r w as c o n n e c te d t o t h e c o p p e r tu b e l e a d i n g t o t h e s e ttlin g

c h a m b e r.

A p i e c e o f c r o s s s e c t i o n p a p e r w as

m o u n te d on a b o a r d b e h in d t h e m an o m ete r t u b e t h e r e b y p r o ­ v id in g a l i n e a r s c a le .

I s o p r o p y l a l c o h o l w as u s e d a s t h e

m an o m ete r f l u i d a n d w as c o l o r e d b y dye fro m a s h e e t o f

44 R ex -O -G raph c a rb o n p a p e r .

T he r e s e r v o i r w as f i l l e d t o a

p o i n t w h e re t h e a l c o h o l r o s e i n t h e m an o m e te r t o a r e a d i n g o f t h r e e o r f o u r i n c h e s i n t h e lo w e r e n d . The m an o m ete r w as now r e a d y f o r u s e b u t i t w o u ld show o n l y t h e d i f f e r e n c e i n p r e s s u r e b e tw e e n t h e s e t t l i n g and th e t h r o a t .

cham ber

To be u s e f u l d u r i n g t e s t s i t w as n e c e s s a r y

to c a lib r a te i t a g a in s t th e th r o a t v e lo c ity .

The c a l i b r a t i o n

c u rv e may be fo u n d i n C h a p te r 7 1 . The t h e o r y b a c k o f t h i s i n s t r u m e n t i s t h a t t h e a i r m ay be t r e a t e d a s an i n c o m p r e s s i b le i s o t h e r m a l f l u i d w i t h i n th e p r e s s u r e ra n g e e n c o u n te re d . a s s u m p tio n i s n e g l i g i b l e .

The e r r o r due t o t h i s

F o r a g iv e n s e t o f c o n d itio n s

B e r n o u l l i ’ s E q u a tio n m ay t h e n b e s t a t e d a s ,

or

The e q u a t i o n o f c o n t i n u i t y f o r an i n c o m p r e s s i b l e i s o t h e r m a l flu id is ,

Thus i f know n.

a n d Ag a r e known t h e v e l o c i t y r a t i o i s a l s o M aking u se o f t h i s r e l a t i o n we may r e w r i t e t h e

B e r n o u l l i E q u a tio n a s ,

45 I f we now d e f i n e s t a t i o n one a s t h e t h r o a t an d s t a t i o n tw o a s t h e s e t t l i n g c h a m b e r, t h e v e l o c i t y i n t h e t h r o a t i s s e e n t o be

i

I t i s now e v i d e n t t h a t

d e p e n d s upon a s i n g l e v a r i a b l e ,

t h e p r e s s u r e d i f f e r e n c e b e tw e e n t h e s e t t l i n g c h am b er a n d t h e t h r o a t , an d t h a t a c a l i b r a t i o n c u rv e can b e draw n w i t h p lo tte d a g a in s t t h i s p re s s u re d if f e r e n c e .

In th e s u b je c t

t u n n e l t h e t h r o a t i s o p e n t o t h e a tm o s p h e re a n d i t s d e n s i t y i s t h e r e f o r e e f f e c t i v e l y a tm o s p h e r ic . fa c to r o f

a ir

A c o rre c tio n

may b e a p p l i e d t o t h e c a l i b r a t i o n c u rv e t o

a c c o u n t f o r v a r i a t i o n s o f a tm o s p h e r ic d e n s i t y fro m t h a t o f f o r w h ic h t h e c u rv e w as d ra w n . II.

VARIABLE-SLOPE INCLINED MANOMETER

T h is i n s t r u m e n t m ay be s e e n i n F ig u r e 9 .

I t is

e s s e n t i a l l y a n a s s e m b ly o f tw o u n i t s su c h a s w as d i s c u s s e d in th e p re v io u s a r t i c l e .

The d i f f e r e n c e l i e s i n t h e f a c t

t h a t t h e s lo p e o f t h e m an o m ete r t u b e s may be v a r i e d .

The

r e s e r v o i r s a r e m o u n te d on t h e fra m e o f t h e i n s t r u m e n t a n d do n o t move w i t h t h e m an o m eter t u b e s .

The s lo p e m ay b e v a r i e d

fro m z e r o t o 6 / 4 0 , t h e s lo p e s c a l e b e in g g r a d u a t e d f o r e a c h 1 /4 0 i n c r e m e n t .

A p lu m b -b o b w as p r o v i d e d f o r l e v e l i n g t h e

i n s t r u m e n t a n d t h e i n i t i a l a lig n m e n t w as o b t a i n e d w i t h t h e a id o f a s u r v e y o r ’s l e v e l . III.

THE PITOT-STATIC TUBE

The f u n d a m e n ta ls o f t h e p i t o t - s t a t i c t u b e h a v e b e e n w e l l e s t a b l i s h e d f o r m any y e a r s and c o n s t i t u t e one o f th e b a s i c t h e o r i e s u s e d i n v e l o c i t y m e a s u re m e n ts .

T y p ic a l p i t o t

t u b e s a n d p i t o t - s t a t i c t u b e s may be fo u n d i l l u s t r a t e d i n a n y e le m e n t a r y t e x t on F l u i d M e c h a n ic s . The p i t o t - s t a t i c tu b e i s a n i n s t r u m e n t c o n s i s t i n g o f tw o c o n c e n t r i c t u b e s , t h e i n n e r t u b e b e in g o pen a t one e n d , t h e o u t e r tu b e b e in g c l o s e d a t t h a t e n d b u t h a v in g o p e n in g s i n i t s w a l l s a t some d i s t a n c e b a c k fro m t h e c l o s e d e n d .

The

o t h e r e n d s o f t h e t u b e s a r e c o n n e c te d t o m a n o m e te rs so t h a t p r e s s u r e s , o r p r e s s u r e d i f f e r e n c e s , m ay be m e a s u re d . The tu b e i s u s e d b y i n s e r t i n g i t i n t o a s tr e a m o f f l u i d w i t h t h e tu b e a x i s p a r a l l e l t o t h e v e l o c i t y v e c t o r t h e v a lu e o f w h ic h i s d e s i r e d .

I f t h e tu b e i s s u f f i c i e n t l y

s m a ll i n d i a m e t e r com pared w i t h t h e d i a m e t e r o f t h e f lo w in g s tr e a m i t s i n t r o d u c t i o n i n t o t h e s tr e a m w i l l h a v e no e f f e c t upon t h e a v e r a g e v e l o c i t y v e c t o r .

H o w ev er, t h e r e w i l l b e a

r e d u c tio n o f v e l o c i t y to z e ro o c c u r r in g a t th e n o se o f th e tu b e .

C o n s id e r in g t h e s e tw o f a c t s , a n d a p p ly i n g B e r n o u l l i ’ s

E q u a tio n t o an i n c o m p r e s s i b le i s o t h e r m a l f l u i d we h a v e , 2 _ „

.

2

47 S in c e Vjl i s z e r o a t t h e n o s e o f t h e t u b e , t h e v e l o c i t y VQ a l o n g s i d e t h e tu b e i s ,

T h u s t h e v e l o c i t y VQ may b e d e te r m in e d i f t h e d e n s i t y and t h e p r e s s u r e d i f f e r e n c e P 1 - PQ a r e know n.

T h is p r e s s u r e

d i f f e r e n c e may be m e a s u re d b y a m a n o m e te r, and f o r a g a s i t i s e q u a l t o w h, w h e re w i s t h e s p e c i f i c w e ig h t o f t h e m ano­ m e te r f l u i d and h i s th e h ead o f t h a t f l u i d .

C o n s is te n t

u n i t s m u st be u s e d . F o r h i g h l y r e f i n e d w o rk t h e p i t o t - s t a t i c tu b e m u st be c a l i b r a t e d .

F o r a v e r a g e w o rk i n ro u g h a i r s u c h c a l i ­

b r a t i o n i s n o t e s s e n t i a l p r o v id e d due c a u t i o n w as u s e d i n t h e d e s i g n an d c o n s t r u c t i o n o f t h e t u b e .

T h is r e q u i r e s

t h a t t h e n o s e o f t h e tu b e be t r u l y h e m i s p h e r i c a l , t h a t t h e s t a t i c o p e n in g s b e e i g h t o r m ore t u b e d i a m e t e r s b a c k from t h e n o s e , a n d t h a t t h e s t a t i c o p e n in g s be s i x t e e n o r m ore tu b e d i a m e t e r s f o r w a r d o f t h e s u p p o r t s te m .^ The tu b e a s c o n s t r u c t e d f o r u s e w i t h t h i s t u n n e l h a s an u n u s u a l l y lo n g s te m .

The r e a s o n f o r t h i s i s o b v io u s when

i t i s c o n s i d e r e d t h a t a v e l o c i t y t r a v e r s e th r o u g h t h e t h r o a t

1 A la n P o p e , W ind- T u n n e l T e s t i n g W ile y an d S o n s , I n c . , 1 $ 4 7 ) , p . 8 0 .

(New Y ork:

Jo h n

48 i s i n o r d e r f o r i n s t r u c t i o n a l p u rp o s e s *

A s h o r t e r ste m

c o u ld h a v e b e e n u s e d i f a s i n g l e c a l i b r a t i o n t r a v e r s e w as th e o n ly c o n s id e r a tio n .

F i g u r e 28 show s t h e d e t a i l s o f t h e

p re s e n t tu b e . IY .

FLOW DIRECTION INDICATOR TUBE

F o r c e s and m om ents w h ic h a r e a p p l i e d t o a m o d e l b y an a i r s t r e a m a r e h i g h l y d e p e n d e n t upon t h e d i r e c t i o n o f t h e a i r s t r e a m r e l a t i v e t o t h e m o d e l. d i r e c t i o n i n a n y g iv e n c a s e i t

I n o r d e r t o d e te r m in e t h i s

i s n e c e s s a r y t o know t h e a i r ­

f lo w d i r e c t i o n w i t h r e s p e c t t o t h e t u n n e l g e o m e try .

If a

%

m o d el i s t h e n a l i g n e d w i t h r e s p e c t t o t h e t u n n e l g e o m e try , i t s a lig n m e n t w i t h r e s p e c t t o t h e a i r s t r e a m i s a l s o know n. The d i r e c t i o n o f t h e a i r s t r e a m f lo w may b e d e te r m in e d w i t h t h e a i d o f a s im p le i n s t r u m e n t .

One s u c h i n s t r u m e n t

c o n s i s t s o f a c i r c u l a r tu b e h a v in g tw o o p e n in g s d r i l l e d i n i t s w a ll. m a n o m e te r.

T h e s e tw o o p e n in g s a r e t h e n c o n n e c te d a c r o s s a In o p e r a tio n , th e tu b e i s r o t a t e d a b o u t i t s

u n t i l t h e d e f l e c t i o n o f t h e m an o m eter i s z e r o .

a x is

The tw o

o p e n in g s a r e t h e n a t e q u a l a n g u l a r d i s p l a c e m e n t s fro m t h e d i r e c t i o n o f t h e a v e r a g e v e l o c i t y o f t h e a p p r o a c h in g a i r ­ s tre a m . The p r e s s u r e s w h ic h a c t a t t h e w a l l o f t h e t u b e a r e c o m p o n e n ts o f t h e t o t a l p r e s s u r e i n t h e s t r e a m .

B e rn o u lli’s

E q u a tio n s t a t e s t h a t t h e t o t a l p r e s s u r e i n a f lo w in g s tr e a m

49 i s t h e sum o f t h e a m b ie n t, o r s t a t i c p r e s s u r e an d t h e dynam ic p r e s s u r e . P,T o t a l S in c e t h e s t a t i c p r e s s u r e a c t s a t b o th o p e n in g s , t h e m ano­ m e te r c a n r e g i s t e r o n l y t h e d i f f e r e n c e i n dynam ic p r e s s u r e c o m p o n e n ts .

To o b t a i n t h e b e s t s e n s i t i v i t y a v a i l a b l e i t i s

o n ly n e c e s s a r y t o d e te r m in e t h e a n g le a t w h ic h t h e dynam ic p r e s s u r e com ponent h a s i t s maximum r a t e o f c h a n g e w i t h a n g le .

F e a t u r e s o f c o n s t r u c t i o n m u st be g o o d , i n v o l v i n g a

sm ooth tu b e s u r f a c e , s m a ll o p e n in g s , an d no i n t e r f e r e n c e e f f e c t s on t h e o p e n in g s . The f lo w a ro u n d t h e t u b e i s e s s e n t i a l l y tw o d im e n s io n a l.

The optim um a n g u l a r p o s i t i o n o f t h e o p e n in g s

c a n t h e r e f o r e be fo u n d b y a p p ly i n g t w o - d im e n s io n a l t h e o r y . T h is t h e o r y s t a t e s t h a t t h e t a n g e n t i a l v e l o c i t y i n t h e f lo w a ro u n d a c i r c u l a r c y l i n d e r i s , 3 v* = 7 ( § - 4 l ) S i n ©

3

w h e re v* i s t h e com ponent o f V n o rm a l t o t h e r a d i u s v e c t o r a t a n g le

0

, 7 i s t h e v e l o c i t y i n t h e m a in s t r e a m , a i s t h e

Roy 7 . S n i t h , " T h e o r e t i c a l F l u i d F lo w ," (A S y l l a b u s , The U n i v e r s i t y o f S o u th e r n C a l i f o r n i a , L os A n g e le s , 1 9 4 9 ) , p p . 5 and 1 7 .

50 ra d iu s o f th e c y lin d e r , R i s th e ra d iu s to a p o in t in th e s t r e a m , an d 9

4

|

i s t h e a n g le b e tw e e n t h e v e l o c i t y v e c t o r

V an d t h e v e c t o r v * .

On t h e s u r f a c e o f t h e c y l i n d e r R

e q u a l s a a n d v* i s t h e a b s o l u t e v e l o c i t y .

A p p ly in g

B e r n o u l l i f s e q u a t i o n b e tw e e n a p o i n t i n t h e f r e e s tr e a m an d th e su rfa c e o f th e c y lin d e r, Pa ♦ | f (8 7 S in

6)2

= PQ 4 | f T

2

Thus th e p r e s s u r e on th e s u r f a c e o f th e c y lin d e r i s ,

Pft = PQ +

- 4Sin2e)

The maximum r a t e o f c h an g e o f P w i t h 6 w i l l o c c u r when a o o d Pg/dO i s z e r o . S in c e PQ, (°, a n d V a r e c o n s t a n t s , d2p / a e 2 = 4 ( ° 7 2 ( c o s 2e - s i n 2 e ) a T h u s , t o o b t a i n t h e maximum s e n s i t i v i t y , t h e a n g le 0 s h o u ld b e 4 5 ° a n d t h e a n g le b e tw e e n t h e tw o o p e n in g s s h o u ld b e 9 0 ° . F i g u r e s 2 9 , 3 0 , a n d 31 show t h e d e t a i l s o f t h e p r e ­ s e n t flo w d i r e c t i o n i n d i c a t o r .

A p r e v i o u s i n s t r u m e n t w as

c o n s t r u c t e d b u t i t w as t o o f l i m s y a n d i t s

a lig n m e n t c o u ld

n o t be m a i n t a i n e d th r o u g h o u t a t e s t . Y.

BOUNDARY LAYER TUBES

One o f t h e t e s t s u s u a l l y a s s o c i a t e d w i t h a e ro d y n a m ic l a b o r a t o r y i n s t r u c t i o n c o n s i s t s o f t h e i n v e s t i g a t i o n o f flo w

51 phenom ena w i t h i n t h e b o u n d a ry l a y e r w h ic h i s a d j a c e n t t o t h e m o d e l.

The u s u a l p i t o t - s t a t i c tu b e i s n o t s u i t a b l e f o r t h i s

w o rk b e c a u s e o f i t s r e l a t i v e l y l a r g e d i a m e t e r .

S n a il

d i a m e t e r t u b e s a r e n e e d e d due t o t h e s m a ll t h i c k n e s s o f t h e b o u n d a ry l a y e r , an d t o p r e v e n t e x c e s s i v e i n t e r f e r e n c e w i t h t h e f lo w . The b o u n d a ry l a y e r t u b e , a s c o n s t r u c t e d , c o n s i s t s o f o n e p i t o t tu b e a n d o n e s t a t i c t u b e , b o th o f w h ic h w e re made fro m h y p o d e rm ic t u b i n g . s e e n i n F ig u r e 2 8 .

D e t a i l s o f t h e i n s t r u m e n t may b e

The i n s t r u m e n t h a s n o t y e t b e e n u s e d a n d

i t i s e x p e c te d t h a t some a d d i t i o n a l b r a c i n g may be n e e d e d t o p r e v e n t e x c e s s i v e v i b r a t i o n o f t h e s m a ll d i a m e t e r t u b i n g . V I.

THE DRAG SPHERES AND THEIR BALANCE SYSTEM

I n g e n e r a l , w i n d - t u n n e l s a r e u s e d so t h a t s m a l l , r e l a t i v e l y in e x p e n s i v e m o d e ls may b e t e s t e d an d t h e i r t e s t r e s u l t s a p p lie d t o th e p r e d ic tio n o f f u l l - s c a l e c h a r a c te r ­ is tic s .

Due t o t h e m e th o d o f p r o d u c in g a w i n d - t u n n e l

v e l o c i t y , t h e u s u a l w i n d - t u n n e l c a n n o t be e x p e c te d t o h a v e t h e same c h a r a c t e r i s t i c s o f a i r f lo w a s a r e f o u n d i n t h e f r e e a tm o s p h e r e .

One o f t h e s e c h a r a c t e r i s t i c s i s t h e

r e l a t i v e tu rb u le n c e o f th e a i r .

I t h a s b e e n fo u n d t h a t t h e

d r a g o f a s p h e r e a t a g iv e n R e y n o ld s Number i s a f f e c t e d b y t h i s r e la tiv e tu rb u le n c e .

A p l o t o f d ra g c o e f f i c i e n t v e rs u s

R e y n o ld s Number show s a c h a r a c t e r i s t i c w h ic h i s a r a t h e r

52 s u d d e n d e c r e a s e i n t h e v a lu e o f t h e c o e f f i c i e n t w i t h i n a s m a ll ra n g e o f R e y n o ld s N u m b ers.

The v a lu e

z 0 .3 o c c u rs

w i t h i n t h i s r a n g e an d t h e C r i t i c a l R e y n o ld s Number h a s b e e n d e f i n e d a s t h a t R e y n o ld s Number a t w h ic h

i s 0 .3 .

f r e e a tm o s p h e re t h i s o c c u r s a t N .R . = 3 8 5 0 0 0 .

In th e

I n t h e w in d -

t u n n e l i t o c c u r s a t a lo w e r R e y n o ld s Number b e c a u s e o f t h e g r e a t e r d e g r e e o f t u r b u l e n c e i n t h e f lo w .

The R e y n o ld s

Number a t w h ic h t h i s phenom enon o c c u r s i n t h e w i n d - t u n n e l i s known a s t h e C r i t i c a l R e y n o ld s Number o f t h e t u n n e l , and i s u s e d t o d e te r m in e t h e E f f e c t i v e R e y n o ld s Number o f a t e s t . I t a l s o p r o v i d e s a m e a s u re o f t h e r e l a t i v e t u r b u l e n c e i n t h e tu n n e l w ith r e s p e c t t o t h a t in f r e e a i r . T he C r i t i c a l R e y n o ld s Number o f a t u n n e l may b e d e t e r ­ m in e d b y t e s t i n g a s p h e r e i n e i t h e r o f two w a y s.

The a c t u a l

d r a g f o r c e may b e m e a s u r e d , o r t h e r a t i o A P /q m ay b e d e t e r ­ m in e d , w h e re

a

P i s th e d if f e r e n c e in p re s s u re a c ro s s th e

s p h e r e a n d q i s t h e dynam ic p r e s s u r e ,

T e s ts have

shown t h a t A P /q = 1 .2 2 w hen C^ = 0 . 3 . The s p h e r e d r a g i n s t a l l a t i o n f o r t h i s t u n n e l h a s b e e n c o n s t r u c t e d so t h a t e i t h e r o r b o t h o f t h e ab o v e m e th o d s may be u sed d u rin g a t e s t .

The t h r e e s p h e r e s w e re c o n s t r u c t e d

o f alu m in u m , e a c h b e in g made h o llo w and i n tw o h a l v e s a s shown i n F ig u r e 3 5 . n o se and a t th e r e a r .

P r e s s u r e h o l e s w e re p r o v id e d a t t h e The s u p p o r t m em ber c o n s i s t s o f two

53 c o n c e n t r i c t u b e s a n d i s i n t u r n s u p p o r te d b y a b a la n c e beam , d e t a i l s o f w h ic h a r e shown i n F ig u r e 3 4 .

The d r a g

f o r c e may b e r e a d on t h e beam i n i n c r e m e n t s o f 0 .0 0 5 p o u n d . The p r e s s u r e s a r e t a k e n o f f t h e s u p p o r t t u b e w h e re i t t h e b a la n c e s t r u c t u r e .

jo in s

R ubber tu b in g i s u sed f o r con­

n e c t i o n s t o a m a n o m e te r. V II.

THE TORQUE MEASURING DEVICE

A te r m known a s t h e E n e rg y R a tio i s n o r m a l ly u s e d i n c o n n e c ti o n w i t h w i n d - t u n n e l s .

I t i s a m e a su re o f t h e

e f f ic ie n c y o f th e tu n n e l and i s d e fin e d a s th e r a t i o o f th e e n erg y o f th e a i r in th e t h r o a t to th e e n e rg y in p u t to th e a ir.

A n o th e r d e f i n i t i o n i n v o l v e s t h e e n e r g y i n p u t t o t h e

m o to r i n p l a c e o f t h e i n p u t t o t h e a i r . The e n e r g y o f t h e a i r i n t h e t h r o a t i s or

1

3

s im p ly qAV,

A, a n d i n d i c a t e s t h e r a t e o f w o rk w h ic h c o u ld be done

by th e a ir s tr e a m w h ile i t

i s b e in g b r o u g h t t o r e s t .

T h is

e n e r g y may b e d e te r m in e d b y s im p le p i t o t - s t a t i c t u b e m e a s u r e ­ m e n ts w h ic h show t h e dynam ic p r e s s u r e , q , an d fro m w h ic h t h e t h r o a t v e l o c i t y , V, may be o b t a i n e d .

A tr a v e r s e o f th e

t h r o a t i s n e c e s s a ry i n o rd e r to o b ta in a v e ra g e v a lu e s . The i n p u t e n e r g y m ay b e o b t a i n e d fro m w a t t - m e t e r m e a s u re m e n ts o r fro m t o r q u e m e a s u re m e n ts . T h is t u n n e l h a s b e e n p r o v id e d w i t h a m eans o f m e a s u r­ i n g t h e t o r q u e o u t p u t o f t h e m o to r .

When t h i s s y s te m i s

54 u s e d t h e r e s u l t a n t p o w er i n p u t i s t h a t t o t h e f a n .

Thus th e

e f f e c t o f th e fa n e f f i c ie n c y w i l l n o t have been c o n s id e re d . The e n e r g y r a t i o , E . R . , a s u s e d h e r e i n w i l l t h e n be d e fin e d a s , E .R . = qAV/550 H . P . f a n The t o r q u e m e a s u r in g d e v ic e c o n s i s t s o f a c o n v e r t e d C h a t i l l o n c o u n tin g s c a l e w i t h s u i t a b l e w e i g h t s , a c h a i n w h ic h l i n k s t h e s c a l e t o t h e m o to r t o r q u e a rm , a n d t h e m eth o d o f m o u n tin g t h e m o to r fra m e on b a l l b e a r i n g s .

The

b a la n c e beam i s g r a d u a t e d i n o n e - e i g h t h o u n c e i n c r e m e n t s . The beam r i d e r c a n b a la n c e a maximum o f t w e n ty o u n c e s . A d d i t i o n a l p a n w e i g h ts w e re p r o v i d e d t o a maximum b a l a n c i n g o f 148 o u n c e s w h ic h i s r o u g h l y t w ic e t h e p o s s i b l e a p p l i e d fo rc e .

The t o r q u e arm i s e i g h t e e n a n d t h r e e - q u a r t e r i n c h e s .

The m o to r s p e e d may be o b t a i n e d w i t h a Frahm V i b r a t i n g - R e e d T a c h o m e te r.

The i n s t a l l a t i o n i s p i c t u r e d i n F ig u r e V III.

8

.

THE MODEL BALANCE SYSTEM

The s y s te m w h ic h w as d e v i s e d f o r m e a s u r in g t h e f o r c e s an d m om ents a s a p p l i e d t o a m o d el i n t h e t u n n e l t h r o a t c o n ­ s i s t s o f f i v e b a la n c e beam s p l u s s u i t a b l e f r a m e s , t e n s i o n w i r e s , an d a m o d el s u p p o r t t o w e r .

As shown i n F i g u r e s 36 t o

3 9 , a m a in s u p p o r t fra m e i s a t t a c h e d d i r e c t l y t o t h e t u n n e l s tru c tu re .

The b a la n c e beam p i v o t s u p p o r t s w e re r i g i d l y

55 a t t a c h e d t o t h e m a in f r a m e .

T h re e l i f t beam s s u p p o r t a

t r i a n g u l a r l i f t - f r a m e th r o u g h t e n s i o n w i r e s .

The d e t e r ­

m i n a t i o n o f t o t a l l i f t f o r c e , p i t c h i n g m om ent, a n d r o l l i n g moment a p p l i e d t o t h e m o d e l i s p o s s i b l e t h r o u g h t h e u s e o f t h e s e t h r e e b e am s. The t r i a n g u l a r l i f t - f r a m e

su p p o rts a " te e * -s h a p e d

d r a g fra m e th r o u g h t h r e e t e n s i o n w i r e s .

From t h e b a r o f t h e

" t e e " tw o t e n s i o n w i r e s l e a d i n an u p s tr e a m d i r e c t i o n t o tw o f o r t y - f i v e d e g re e w i r e s a n d t h e n c e v e r t i c a l l y upw ard t o t h e tw o d r a g b e am s.

T h e se beam s p e r m i t t h e d e t e r m i n a t i o n o f t h e

t o t a l d ra g f o r c e an d t h e yaw ing m om ent. The m o d el s u p p o r t to w e r w as m o u n ted on t h e d r a g " t e e " fra m e a n d e x te n d s v e r t i c a l l y upw ard i n t o t h e t u n n e l t h r o a t . P r o v i s i o n w as made f o r c o n t r o l l i n g t h e a n g le o f a t t a c k o f t h e m o d el fro m t h e u n d e r s i d e o f t h e d ra g f r a m e .

The e n t i r e

a s s e m b ly may be rem oved fro m t h e t u n n e l b y re m o v in g t h r e e sc re w s. The g e n e r a l foxm o f t h e s y s te m o f e q u a t i o n s f o r t h i s b a la n c e s y s te m i s i n d i c a t e d b e lo w . on t h e m o d e l.

L e t D be t h e t o t a l d ra g

T h en ,

D — Dj ^ Dg w h e re D-^ an d Dg a r e t h e f o r c e s m e a s u re d b y t h e tw o d r a g b e am s. T hen,

L et M

b e t h e y aw in g moment a p p l i e d t o t h e m o d e l.

56 My = < »i - % > | w h e re 1 i s t h e d i s t a n c e b e tw e e n t h e tw o d r a g b e am s. b e t h e t o t a l l i f t o f t h e m o d e l.

L et L

T hen,

L ~ Lp 4 Lg 4 Lg w h e re L-^ a n d Lg a r e t h e

f o r c e s m e a s u re d b y t h e tw o f r o n t

l i f t beam s w h ic h a r e a d j a c e n t t o t h e d r a g b e am s, an d

is

t h e f o r c e m e a s u re d b y t h e l i f t beam w h ic h i s f a r t h e s t down­ s tre a m .

L e t Mp be t h e p i t c h i n g moment a p p l i e d t o t h e m o d e l.

T hen, Mp 4 DA = L3C w h e re A i s t h e d i s t a n c e

(Lx 4 Lg)B o f t h e m o d el above

t h e d ra g f r a m e ,

B i s a d i s t a n c e m e a s u re d u p s tr e a m fro m t h e m o d el s u p p o r t to w e r t o t h e f r o n t l i f t w i r e s , and C i s t h e d i s t a n c e down­ s tr e a m fro m t h e to w e r t o t h e r e a r l i f t w i r e . r o l l i n g moment a p p l i e d t o t h e m o d e l.

L e t Mp b e t h e

T h en ,

■* SA = (Lx - La ) § w h e re S i s t h e s i d e f o r c e a p p l i e d t o t h e m o d el and G i s t h e d i s t a n c e b e tw e e n t h e tw o l i f t beam s L^ a n d Lg .

The f o r c e S

i s i n d e t e r m i n a t e i n t h i s s y s te m , an d t h u s t h e co m p u ted r o l l ­ i n g moment i s t a k e n a s (Lp - L g)§* a m o u n tin g t o t h e v a lu e o f t h e SA p r o d u c t .

in tr o d u c e s an e r r o r W ith a p r o p e r l y

a l i g n e d m o d el t h e v a l u e o f S i s u s u a l l y q u i t e s m a ll and i s

57 fre q u e n tly n e g le c te d .

T hus t h e e r r o r i n

w i l l u s u a l l y be

s m a ll. IX .

INSTRUMENT CONSTRUCTION DIFFICULTIES

M ost o f t h e i n s t r u m e n t c o n s t r u c t i o n f o llo w e d t h e u s u a l l i n e o f f a b r i c a t i o n i n v o l v i n g t h e w o rk in g o f m e t a l an d s o ld e rin g .

O n ly one d i f f i c u l t y w o r th y o f m e n tio n w as e n ­

c o u n te r e d .

T h is o c c u r r e d d u r i n g t h e c o n s t r u c t i o n o f t h e

f lo w d i r e c t i o n i n d i c a t o r .

The d e s i g n c a l l e d f o r a t h r e e -

q u a r t e r in c h b r a s s t u b e on w h ic h a o n e - s i x t e e n t h i n c h b r a s s r o d w as t o be s o l d e r e d , t h e r o d b e in g p a r a l l e l t o t h e t u b e a x i s an d h a v in g s o l d e r a p p l i e d a lo n g i t s F ig u r e 2 9 .

e n tir e le n g th .

B o th p i e c e s w e re t h i r t y - f o u r i n c h e s l o n g .

To

a l i g n t h e r o d i t w a s d e s i r e d t o g ro o v e t h e l e n g t h o f t h e tu b e t o a d e p th o f 0 .0 1 0 i n c h .

B o th t h e p r o c e s s o f g r o o v in g

a n d t h e a p p l i c a t i o n o f h e a t w o u ld w arp t h e t u b e .

To o v e r ­

come t h i s d i f f i c u l t y t h e t u b e w as w ra p p e d i n a s b e s t o s , an d h u n g w i t h i t s a x i s v e r t i c a l , a h e a v y w e ig h t b e in g s lu n g fro m t h e lo w e r e n d o f t h e t u b e .

An e l e c t r i c a l h e a t i n g e le m e n t

w as t h e n i n s e r t e d th r o u g h t h e t u b e .

The t u b e t e m p e r a t u r e

w as r a i s e d t o 4 5 0 °F a n d m a i n t a i n e d a t t h a t t e m p e r a t u r e f o r a p e rio d o f fo u r h o u rs.

T h is h e a t t r e a t m e n t rem o v ed p r a c t i c a l ­

l y a l l o f t h e r e s i d u a l s t r e s s e s due t o m a n u f a c t u r e . g ro o v e w as t h e n m i l l e d i n t h e s i d e o f t h e t u b e .

The

The t u b e

w as a g a i n s u s p e n d e d w i t h t h e h e a t e r a n d w e ig h t i n p l a c e , an d

t h e g ro o v e s u r f a c e s w e re t i n n e d w i t h s o f t s o l d e r .

The o n e -

s i x t e e n t h i n c h r o d w as a l s o t i n n e d , a n d w as t h e n p l a c e d on t h e t u b e a n d h e l d b y a w ra p p in g o f w i r e .

The s o l d e r i n g w as

t h e n c o m p le te d w i t h t h e a i d o f ^ t h e h e a t i n g e le m e n t.

In ­

s p e c t i o n o f t h e f i n a l p r o d u c t show ed no a p p r e c i a b l e w a r p in g .

CHAPTER VI TUHNEL TESTS AND CALIBRATION B e f o r e a w i n d - t u n n e l can be u s e d f o r t h e g e n e r a l t e s t i n g o f o b j e c t s i n t h e a i r s tr e a m t h e c h a r a c t e r i s t i c s o f t h e t u n n e l i t s e l f m u st b e know n.

The d e t e r m i n a t i o n o f t h e s e

c h a r a c t e r i s t i c s i n v o l v e s s e v e r a l t e s t s a n d i s a r a t h e r lo n g a n d a rd u o u s p r o c e d u r e .

I f t h e t u n n e l i s t o be u s e d f o r

c o m m e rc ia l t e s t i n g i t i s i m p e r a t i v e t h a t a l l p o s s i b l e i n ­ f o r m a t io n b e o b t a i n e d so t h a t m o d i f i c a t i o n s may b e em p lo y ed to a t t a i n th e h ig h e s t p o s s ib le e f f ic ie n c y .

The t e s t i n g o f

t h e s u b j e c t t u n n e l d i d n o t i n c l u d e a l l t e s t s w h ic h w o u ld be made on a c o m m e rc ia l t u n n e l .

T h o se w h ic h w ere o m it t e d w e re

a l l t e s t s i n v o l v i n g p r e s s u r e c h a n g e s a n d f lo w c h a r a c t e r ­ i s t i c s in th e body o f th e tu n n e l o th e r th a n a t th e re g io n o f th e t h r o a t . The a c t u a l t e s t d a t a an d c o m p u ta tio n s o f t h e t e s t s w h ic h w e re m ade a r e c o n t a i n e d i n A p p en d ix A.

T h is c h a p t e r

d e a ls o n ly w ith th e g e n e r a l d e s c r i p t io n o f th o s e t e s t s and c o n ta in s t h e i r r e s u l ta n t c u rv e s . I.

IN IT IA L TESTS

Upon c o m p le tio n o f t h e t u n n e l i t w as d e s i r e d t o know w h e th e r o r n o t t h e m o to r w as t u r n i n g a t t h e p r o p e r s p e e d , a n d co n su m in g t h e c o r r e c t am ount o f po w er a s d e te r m in e d b y

60 i t s ra tin g .

S im p le t e s t s i n v o l v i n g t h e u s e o f t h e Frahm

T a c h o m e te r show ed t h a t t h e maximum s p e e d w as low b y a p p r o x i ­ m a t e l y 200 r e v o l u t i o n s p e r m i n u t e .

T h is w as c o r r e c t e d b y

a d j u s t i n g t h e f a n b l a d e s t o a lo w e r b l a d e a n g l e .

A d d itio n a l

t e s t s w e re t h e n made a n d t h e maximum s p e e d w as fo u n d t o b e a p p r o x i m a t e ly 1 ,8 0 0 r e v o l u t i o n s p e r m in u t e , w h ic h i s t h e r a te d sp eed .

The d a t a o f t h e s e t e s t s a r e c o n t a i n e d i n

T a b l e s X a n d X I. As h a s b e e n s t a t e d p r e v i o u s l y , t h e t o r q u e b a la n c e c o n s i s t e d o f a c o n v e r t e d C h a t i l l o n c o u n ti n g beam , w i t h s p e c i a l beam an d p a n w e i g h t s . on t h i s beam t o w e ig h t.

c o rre la te i t s

S e v e r a l t e s t s w e re c o n d u c te d i n d i c a t e d w e ig h t w i t h t r u e

The r e s u l t a n t c a l i b r a t i o n w as fo u n d t o h a v e a

n e g l i g i b l e v a r i a t i o n fro m t r u e - w e i g h t v a l u e s , on t h e b a s i s o f t h e u s e w h ic h w o u ld b e m ade o f i t .

The t e s t d a t a a r e

c o n ta in e d i n T a b l e s X I I I an d XIV o f A p p e n d ix A, and t h e c a l i b r a t i o n d a t a a r e on p a g e s 61 an d 62 o f t h i s c h a p t e r . S e v e r a l t e s t s w e re t h e n c o n d u c te d f o r t h e p r im a r y p u r p o s e o f d e te r m i n i n g t h e p o w er c o n d i t i o n s .

D u rin g t h e s e

t e s t s t h e p o w er i n - p u t t o t h e m o to r w as o b t a i n e d b y w a t t ­ m e t e r s , t h e p o w e r o u t - p u t fro m t h e m o to r w as fo u n d fro m t h e t o r q u e b a la n c e an d Frahm t a c h o m e t e r , an d s u f f i c i e n t i n ­ f o r m a t i o n w as t a k e n fro m a p i t o t - s t a t i c t u b e a n d t h e s t a t i c p l a t e m a n o m ete r t o d e te r m in e a v e l o c i t y c u r v e . t h e s e t e s t s a r e c o n t a i n e d i n T a b l e s X II a n d XV.

The d a t a o f T h e ir

61

TABLE I TORQUE BALANCE CALIBRATION* R id e r I n d ic a te d O unces

T ru e W eig h t O unces

2

2 .0 0 8

4

3 .9 8

6

6 .0 0

8

7 .9 9

10

9 .9 6

12

1 1 .9 6

14

1 3 .9 2

16

1 5 .9 3

18

1 7 .9 3

20

1 9 .9 0

* D a ta fro m T a b le X I I I .

62 BALANCE CALIBRATION CURVE RIDER INDICATED WEIGHT TRUE WEIGHT CLOSED RETUSH STUDEHT WIHD TUNNEL THROAT SIZE 8 4 " x l5 " UNIVERSITY Off SOUTHERN CALIffORNIA SEPT. 3 0 , 1949 ROT V. SMITH

CHART I

- O unces

D a ta fro m T a b le I

T ru e W eig h t O z.

Weight

Pan T /e ig h t No -

1 5 .9 0 1 5 .9 1 3 1 .7 8 3 1 .8 3 3 1 .8 3

1 2

I n d ic a te d

3 4 5

= 1 6 . 3 0

1 .3 5 1 .6 0 3 .9 0 3 .0 5 2 .1 5 2 .1 5 4 .3 0 3 .7 0 4 .0 5 6 .3 5 4 .7 5 4 .6 0 5 .3 5 5 .1 5 6 .9 0 8 .3 0 7 .9 5 7 .9 0

©

®

h

✓h

2 6 .0 5 2 5 .8 0 2 3 .5 0 2 4 .3 5 2 5 .2 5 2 5 .2 5 2 3 .1 0 2 3 .7 0 2 3 .3 5 2 1 .0 5 2 2 .6 5 2 2 .8 0 2 2 .0 5 2 2 .2 5 2 0 .5 0 1 9 .1 0 1 9 .4 5 1 9 .5 0

5 .1 0 5 .0 8 4 .8 5 4 .9 3 5 .0 3 5 .0 3 4 .8 0 4 .8 7 4 .8 3 4 .5 9 4 .7 6 4 .7 7 4 .7 0 4 .7 1 4 .5 3 4 .3 7 4 .4 1 4 .4 1

N et In .A l. 2 7 .4 0 - ©

2 2 .9 7

VS td

4 .7 6

•

I

.9 8 8 '^O bs.

A v erag e V e l o c i t y a t O b s e rv e d C o n d i t i o n s , 7 7 .6 F .P .S . A v e rag e V e l o c i t y a t S ta n d a r d C o n d i ti o n s ,

7 6 .6 F .P .S .

A v e rag e S t a t i c P l a t e D e f l e c t i o n , 2 2 . 97 I n . A l . on s lo p e

•

125 X.

VELOCITY TRAVERSE AND ENERGY RATIO CALIBRATION TESTS

V e l o c i t i e s i n f l u i d f lo w a r e o u t a g iv e n f lo w a r e a .

seldom u n ifo r m th r o u g h ­

W h ile t h e o r y i n d i c a t e s t h a t t h e

v e l o c i t y v a r i a t i o n th r o u g h an a r e a i s u n i f o r m ,3 t e s t s show t h a t t h e a c t u a l f lo w d o e s n o t e x h i b i t t h i s phenom enon.

The

a c c e p t e d m eth o d f o r d e te r m i n i n g t h e a v e r a g e v e l o c i t y th r o u g h an a r e a

4

i s to

s u b d iv id e th e a r e a i n to

s m a ll r e g i o n s , d e t e r ­

m in e t h e v e l o c i t y i n e a c h r e g i o n , t a k e t h e sum o f t h e s e v e l o c i t i e s an d d i v i d e by t h e num ber o f r e g i o n s ,

f o r a g iv e n

s e t o f c o n d itio n s , s in c e th e v e l o c i t y i s o b ta in e d by th e e q u a t i o n V - K / h ~ , o n e n e e d o n l y d e te r m in e t h e a v e r a g e v a lu e o f h z a n d t h e n a p p ly t h e c o n s t a n t .

E q u a tio n s A -7 an d

A-8 a r e a p p l i c a b l e t o t h e s e t e s t s . I n w o rk in g w i t h w i n d - t u n n e l s i t i s d e s i r a b l e t o h a v e some m e a s u re o f t h e p e rfo rm a n c e o f t h e t u n n e l .

S ta n d a r d

TT

R. C. B in d e r , F l u i d M e c h a n ic s ( s e c o n d e d i t i o n ; New Y ork: P r e n t i c e - H a l l , I n c . , 1 9 4 9 ) , p . 1 0 0 . 4

W illia m H. S e v e r a s a n d Howard E . D e g l e r , S te a m , A i r , a n d Gas P ow er ( f o u r t h e d i t i o n ; New Y ork: Jo h n W ile y an d S o n s , I n c . , 1 9 4 8 ) , p . 2 2 4 .

126

p r a c t i s e m akes u se o f a te r m known a s t h e E n e rg y R a tio w h ic h i s d e fin e d by th e e q u a tio n , Er r qA V /550(H P)i l u The p r o d u c t qAV/550 i s t h e pow er w h ic h c o u ld be e x p e n d e d b y t h e a i r i n t h e t h r o a t i f i t w e re s u d d e n ly b r o u g h t t o r e s t . V a r i a t i o n s a r e fo u n d i n t h e s e l e c t i o n o f t h e i n p u t h o r s e ­ p o w er t e r m .

I n some c a s e s t h e e l e c t r i c a l i n p u t a s i n d i c a t e d

by w a tt-m e te rs i s u se d .

In o th e r c a se s th e e f f ic ie n c ie s o f

t h e m o to r and t h e f a n a r e i n c l u d e d .

F o r t h e p r e s e n t w ork

t h e i n p u t h o r s e p o w e r t o be u s e d i s t h a t w h ic h r e a c h e s t h e fan .

T hus t h e f a n e f f i c i e n c y w i l l n o t h a v e b e e n c o n s i d e r e d

an d t h e i n p u t p o w er may b e m e a s u re d b y t h e t o r q u e b a la n c e s y s te m . The t u n n e l c o n d i t i o n s f o r T e s t s X II t o XXI i n c l u s i v e w e re a s f o l l o w s : 1.

Fan b l a d e a n g le 1 4 ^

a t 0 .7 5 R.

2.

M o d if ie d t h r o a t c o n f i g u r a t i o n .

In tr a v e r s in g th e t h r o a t f o r th e v e lo c it y d e te r ­ m in a t i o n t h i r t y t e s t p o i n t s w e re u s e d .

The l o c a t i o n s o f

t h e s e p o i n t s i n t h e t h r o a t a r e shown b e lo w .

5 A lan P o p e , W in d -T u n n e l T e s t i n g (New Y ork: W ile y an d S o n s , I n c . , 1 9 4 7 ), p . 9 2 .

Jo h n

127 TABLE XXII

TEST XTI

VELOCITY AND ENERGY RATIO CALIBRATION S p eed Tap 1 B a ro m e te r 2 9 .8 8 ” Hg. P i t o t M a n o m eter, t a r e h = 2 1 .8 5 ” , s lo p e 4 /4 0 S t a t i c - P l a t e M an o m eter, t a r e h s = 4 .6 0 ” T o rq u e B a la n c e T a r e , 1 ^ , 4 g , N e t t a r e 3 g o z .

■

---------

T est P o s itio n D a ta 1

I n .A l. Rdg. D a ta 1 4 .9 0

2

■© h In .A l. Rdg. D a ta

~~f> T h ro a t Temp. D a ta

'€ ) .......

~m w ~ .... m “

W

T o rq u e R .P .M . h F o rc e D e fl. o z .R d g . D a ta 2 1 ^ 8 5 -© v/© D a ta

1 4 .0 5

69

38§

1 ,1 7 0

7 .8 0

2 .7 9

1 4 .9 5

1 3 .8 0

69

38§

1 ,1 7 0

8 .0 5

2 .8 4

3

1 4 .9 0

1 3 .7 0

69

38§

1 ,1 7 0

8 .1 5

2 .8 5

4

1 4 .9 5

1 3 .6 5

69

38§

1 ,1 7 5

8 .2 0

2 .8 6

5

1 4 .9 5

1 3 .7 5

69

38$

1 ,1 7 0

8 .1 0

2 .8 5

6

1 5 .0 5

1 3 .8 5

69

38$

1 ,1 7 0

8 .0 0

2 .8 3

7

1 5 .0 5

1 4 .3 5

69

38$

1 ,1 7 0

7 .5 0

2 .7 4

8

1 4 .9 5

1 4 .2 5

70

38$

1 ,1 7 0

7 .6 0

2 .7 6

9

1 4 .9 5

1 4 .0 5

70

38$

1 ,1 7 0

7 .8 0

2 .7 9

10

1 4 .9 5

1 4 .0 0

70

38$

1 ,1 7 0

7 .8 5

2 .8 0

11

1 4 .9 0

1 4 .2 5

70

38$

1 ,1 8 0

7 .6 0

2 .7 6

12

1 4 .9 0

1 4 .3 0

70

38$

1 ,1 8 0

7 .5 5

2 .7 5

13

1 4 .9 0

1 4 .7 5

70

38$

1 ,1 8 0

7 .1 0

2 .6 6

14

1 4 .9 0

1 4 .9 0

70

38$

1 ,1 8 0

6 .9 5

2 .6 4

15

1 4 .8 5

1 4 .7 0

70

38$

1 ,1 8 0

7 .1 5

2 .6 7

16

1 4 .9 0

1 4 .5 5

70

38$

1 ,1 8 5

7 .3 0

2 .7 0

17

1 5 .0 0

1 4 .5 0

70

39

1 ,1 8 5

7 .3 5

2 .7 1

18

1 4 .9 5

1 4 .4 0

70

39

1 ,1 8 0

7 .4 5

2 .7 3

128 TABLE XXII (c o n tin u e d )

CD

TEST XXI

© © ® T o rq u e R .P .M . h F o rc e D e f l. o z .R d g . In .A l. D a ta 2 1 .8 5 - © D a ta

I n .A l. Rdg. D a ta

© h I n .A l. R dg. D a ta

19

1 4 .7 0

1 5 .3 0

70

38§

1 ,1 7 0

6 .5 5

2 .5 6

30

1 4 .6 5

1 4 .9 5

70

38§

1 ,1 7 0

6 .9 0

2 .6 3

21

1 4 .7 0

1 4 .8 5

70

39

1 ,1 7 0

7 .0 0

2 .6 5

22

1 4 .8 0

1 4 .8 0

70

39

1 ,1 7 0

7 .0 5

2 .6 6

23

1 4 .9 0

1 4 .8 0

70

39

1 ,1 7 0

7 .0 5

2 .6 6

24

1 4 .8 5

1 5 .1 5

70

39

1 ,1 7 0

6 .7 0

2 .5 9

25

1 4 .6 0

1 5 .7 0

70

38§

1 ,1 7 0

6 .1 5

2 .4 8

26

1 4 .5 0

1 5 .6 0

70

38§

1 ,1 7 0

6 .2 5

2 .5 0

27

1 4 .5 5

1 5 .5 0

70

38g

1 ,1 7 0

6 .3 5

2 .5 2

28

1 4 .7 0

1 5 .4 5

70

38§

1 ,1 7 0

6 .4 0

2 .5 3

29

1 4 .7 5

1 5 .5 0

70

38§

1 ,1 7 0

6 .3 5

2 .5 2

30

1 4 .6 5

1 5 .9 0

70

38g

1 ,1 7 5

5 .9 5

2 .4 4

A v erag e

1 4 .8 4

6 9 .8

38.6 9 6

1 ,1 7 3 . 3

2 .7 1 6

1 ,1 7 3 . 3

2.716

T est P o s itio n D a ta

^s

T a re

4 .6 0

N et

1 0 .2 4

© T h ro at Temp. 0 jg» D a ta

2 1 .8 5

/h v/®

3 .2 5 6 9 .8

3 5 .4 4 6

129

41

42

43

44

45

46

f3 —

47

48

49

410

411

4 12

+13

f 14

to 1— 1

4 17

418

-3 —

419

4 20

4 21

4 22

4

23

+ 24

—

4 25

426

+27

*28

+ 29

430

i +6

1 +1 0

-6

i

1 -1 0

lO 1—1

__

1-6

-6

-2

1

1‘ + 21 9Q8

He s u i t s o f T e s t X I I I S t a t i c - P l a t e D e f l e c t i o n : 1 1 .7 s l o p e - i n c h e s o f a l c o h o l V0 b s . : 5 4 P . P . S .

v S t d . = 5 3 - 6 Y -P -S .

SR = 0 .9 0 8

The c a l i b r a t i o n c u r v e s from T e s t s X II t o XXL i n c l u s i v e may be fou n d in C h ap ter V I.

134 TABLE XXIV

TEST XIV

VELOCITY AND ENERGY RATIO CALIBRATION S p eed Tap 3 B a ro m e te r 2 9 .7 8 " Hg. P i t o t - M a n o m e te r , t a r e h - 2 1 .8 0 , s lo p e = 4 /4 0 S t a t i c - P l a t e M an o m eter, t a r e h s = 4 .6 0 T o rq u e B a la n c e T a r e , 2 § , 5 g , N e t 4g o z .

D a ta

^s I n .A l. Bdg. D a ta

(3> h I n .A l. Rdg. D a ta

© T h ro at Tem p. Oj* D a ta

1

1 7 .8 0

1 1 .8 0

64

45^

1 ,3 1 0

1 0 .0 0

3 .1 6

2

1 7 .8 0

1 1 .5 5

64

45^

1 ,3 1 0

1 0 .2 5

3 .2 0

3

1 7 .7 5

1 1 .3 5

65

4 4

1 ,3 2 0

1 0 .4 5

3 .2 4

4

1 7 .7 0

1 1 .4 0

65

4 4

1 ,3 1 5

1 0 .4 0

3 .2 2

5

1 7 .8 0

1 1 .4 5

65

45 §

1 ,3 1 5

1 0 .3 5

3 .2 2

6

1 7 .8 0

1 1 .6 5

65

45§

1 ,3 1 5

1 0 .1 5

3 .1 8

7

1 7 .7 0

1 2 .3 0

65

45§

1 ,3 1 5

9 .5 0

3 .0 8

8

1 7 .7 0

1 2 .2 0

65

45§

1 ,3 2 5

9 .6 0

3 .1 0

9

1 7 .7 0

1 2 .0 0

65

«g

1 ,3 1 5

9 .8 0

3 .1 3

10

1 7 .7 0

1 1 .9 0

65

45§

1 ,3 1 5

9 .9 0

3 .1 5

11

1 7 .7 0

1 2 .0 0

65

45§

1 ,3 1 5

9 .8 0

3 .1 3

12

1 7 .7 0

1 2 .1 0

65

1 ,3 1 0

9 .7 0

3 .1 1

13

1 7 .6 0

1 2 .7 5

65

45§

1 ,3 2 0

9 .0 5

3 .0 1

14

1 7 .6 0

1 2 .9 0

65

1 ,3 1 5

8 .9 0

2 .9 8

15

1 7 .6 0

1 2 .7 5

65

45§ , c6 45 b

1 ,3 1 5

9 .0 5

3 .0 1

16

1 7 .6 5

1 2 .5 5

65

45§

1 ,3 1 5

9 .2 5

3 .0 4

17

1 7 .6 5

1 2 .5 5

65

4 4

1 ,3 1 5

9 .2 5

3 .0 4

18

1 7 .7 0

1 2 .4 5

65

46

1 ,3 1 5

9 .3 5

3 .0 6

7 3 ~ T est P o s itio n

(D (D T o rq u e R .P .M . h F o rc e D e fl. o z .R d g . I n .A l. D a ta D a ta 2 1 .8 0 - ®

135 TABLE XXIV (c o n tin u e d )

©

©

'Fan : B N /5 3 ,8 5 0 = 5 9 . 0 0 ( l , 6 0 7 ) / 5 3 , 8 5 0 = 1 . 7 6 h . p . Ew = W z P™ Z = 1 »858 H 550 H . P . pan 1 , 1 0 0 H . P . yan 1 ,1 0 0 (1 .7 6 )

= 0 .9 5 6

R e s u lts o f T e s t X 7 III S t a t i c - P l a t e D e f l e c t i o n I 1 8 .6 2 s l o p e - i n c h e s o f a l c o h o l V q^s

—6 8 .6 f .p .s .

^ S t d . “ 6 7 .5 f . p . s .

S g = 0 .9 5 6 The c a l i b r a t i o n c u r v e s o f T e s t s XEI t o 2X1 i n c l u s i v e may­ be foun d in C hapter 7 1 .

149 TABLE XXIX

TEST XIX

VELOCITY ANT) ENERGY RATIO CALIBRATION S p eed Tap 8 B a r o m e te r, 2 9 .6 8 * Hg. P i t o t - M a n o m e te r , t a r e h = 2 1 .6 5 , s l o p e 4 /4 0 S t a t i c - P l a t e M an o m eter, t a r e h s z 4*60 r 7 p T o rq u e B a la n c e T a r e , S g , 5 g , N et 4g o z .

D a ta

19

2 4 .2 5

8 .9 0

75

66

1 ,6 6 5

1 2 .7 5

3 .5 7

20

2 4 .0 5

8 .2 5

75

66

1 ,6 6 0

1 3 .4 0

3 .6 6

21

2 4 .1 0

8 .0 5

75

66

1 ,6 5 0

1 3 .6 0

3 .6 9

22

2 4 .2 0

8 .0 0

76

66

1 ,6 6 0

1 3 .6 5

3 .7 0

23

2 4 .4 0

7 .9 5

76

1 ,6 5 5

1 3 .7 0

3 .7 0

24

2 4 .3 5

8 .5 0

76

66 § 4 66 §

1 ,6 5 0

1 3 .1 5

3 .6 2

25

2 4 .1 0

9 .6 0

76

66 §

1 ,6 5 5

1 2 .0 5

3 .4 8

26

2 3 .9 0

9 .5 0

76

66i

1 ,6 6 0

1 2 .1 5

3 .4 8

27

2 3 .9 0

9 .1 5

76

1 ,6 6 0

1 2 .5 0

3 .5 4

28

2 4 .1 0

9 .1 0

76

66§

1 ,6 5 5

1 2 .5 5

3 .5 4

29

2 4 .2 5

9 .1 5

76

665

1 ,6 5 0

1 2 .5 0

3 .5 4

30

2 4 .2 0

9 .9 0

76

66§

1 ,6 5 0

1 1 .7 5

3 .4 3

A v erag e

2 4 .4 8

7 5 .8

6 6 .1 2 5 1 ,6 6 2 .

© T est P o s itio n

T a re N et

4

4 .6 0

4 .2 5 0

1 9 .8 8

5 3 5 . 8 °R 61.875

1 ,6 6 3

8

sir v/@

3 .7 4

3 .7 4

151 V e l o c i t y E q u a t i o n , Vy p > s

= 5 8 . 9 J s & S & i ' ) J £ . __ Pb S td .

=A W

7 0bs

7

f e &

I S

=

Jh~

° - 322

- 5 8 . 9 ( 0 . 3 2 2 ) 3 . 7 4 — 7 1 .0 f . p . s .

S td . =

5 8 ,9

< ^ S ’ = 5 8 .9 ( 0 . 3 1 6 ) 3 . 7 4 = 6 9 .6 f . p . s .

(°S td .

-

0 . 0 0 3 5 8 ( g g #g

g

= 0 .0 0 S 3 9

b S td . (°Av|b s . = 0 .0 0 2 2 9 ( 2 .5 ) ( 7 1 . 0 ) 3 = 2 ,0 5 0 H . P . F an = J N /5 3 ,8 5 0 = 6 1 . 8 8 ( l , 6 6 3 ) / 5 3 ,8 5 0 = 1 .9 1 h . p . E . qAv H " 550

_ C x r5 _ 2 ,0 5 0 " 1 ,1 0 0 H . P . j ^ " 1 ,1 0 0 ( 1 .9 1 )

. ”

’

Ha s u i t s o f T e s t XIX S t a t i c - P l a t e D e f l e c t i o n Z 1 9 .8 8 s l o p e - i n c h e s o f a l c o h o l

V0 b s . =

71#0

f *P# s *

VS t d . “

6 9 *6

f *P# s *

SR = 0 .9 7 5

The c a l i b r a t i o n c u r v e s from T e s t s X II t o XXI i n c l u s i v e may be fo u n d in C h ap ter V I.

152 TABLE XXX

TEST XX

VELOCITY AND ENERGY RATIO CALIBRATION S p eed Tap 9 B a r o m e te r, 2 9 .6 8 * H g. P ito t- M a n o m e te r , t a r e h = 2 1 .6 5 , s l o p e 4 /4 0 S t a t i c - P l a t e M an o m eter, t a r e h s i 4 .6 0 „2 T o rq u e B a la n c e T a r e , 2 § , 5 g , N et 4g oz.

© © © h T o rq u e R .P.M . D e fl. F o rc e I n . A l. o z .R d g . D a ta 2 1 .6 5 - ® D a ta

® v /h -

1

725

1 6 .5 5

4 .0 7

70§

1

725

1 7 .0 5

4 .1 3

75

7Q |

1

730

1 7 .3 5

4 .1 6

4 .3 0

75

70|

1

725

1 7 .3 5

4 .1 6

2 6 .4 0

4 .6 0

75

70|

1

730

1 7 .0 5

4 .1 3

6

2 6 .4 5

4 .8 5

75

70§

1

730

1 6 .8 0

4 .1 0

7

2 6 .3 0

6 .0 5

75

7°|

1

730

1 5 .6 0

3 .9 5

8

2 6 .2 5

5 .7 0

75

70§

1

730

1 5 .9 5

3 .9 9

9

2 6 .2 0

5 .3 0

75

70§

1

725

1 6 .3 5

4 .0 4

10

2 6 .1 5

5 .2 0

75

70|

1

725

1 6 .4 5

4 .0 6

11

2 6 .2 5

5 .5 0

75

70§

1

720

1 6 .1 5

4 .0 2

12

2 6 .2 0

5 .8 0

75

70|

1

720

1 5 .8 5

3 .9 8

13

2 5 .8 0

6 .9 0

75

70§

1

720

1 4 .7 5

3 .8 4

14

2 5 .9 0

7 .1 0

75

70|

1

725

1 4 .5 5

3 .8 2

15

2 5 .8 0

6 .7 0

75

70§

1

725

1 4 .9 5

3 .8 6

16

2 5 .8 5

6 .5 0

75

70§

1

725

1 5 .1 5

3 .8 9

17

2 6 .1 5

6 .3 5

75

70§

1

725

1 5 .3 0

3 .9 2

18

2 6 .0 0

6 .3 5

75

70§

1

725

1 5 .3 0

3 .9 2

© ^s I n .A l. Rdg. D a ta

© h I n .A l. Rdg. D a ta

© T h ro at Temp. O]? D a ta

1

2 6 .3 5

5 .1 0

75

70§

2

2 6 .4 0

4 .6 0

75

3

2 6 .4 0

4 .3 0

4

2 6 .4 0

5

© T est P o s itio n D a ta

153 TABLE X X X (c o n tin u e d )

Q

©

T est P o s itio n D a ta

^s I n .A l. R dg. D a ta

(£>

h T h ro a t I n . A l . Temp. oy R dg. D a ta D a ta

19

2 5 .7 0

7 .8 0

75

SO

2 5 .7 0

7 .2 0

75

21

2 5 .6 5

7 .0 0

75

22

2 5 .8 0

6 .9 0

23

2 5 .8 5

24

TEST XX

© ©

T o rq u e R .P .M . h F o rc e D e fl. o a .R d g . I n .A l. D a ta D a ta 2 1 .6 5 - 0

® V iT

1 ,7 2 0

1 3 .8 5

3 .7 2

1 ,7 2 5

1 4 .4 5

3 .8 0

70§

1 ,7 2 0

1 4 .6 5

3 .8 3

75

70§

1 ,7 2 0

1 4 .7 5

3 .8 4

7 .0 0

75

70§

1 ,7 2 0

1 4 .6 5

3 .8 3

2 5 .8 0

7 .6 0

75

70f

1 ,7 2 0

1 4 .0 5

3 .7 5

25

2 5 .5 0

8 .6 0

75

70§

1 ,7 2 0

1 3 .0 5

3 .6 1

26

2 5 .4 0

8 .5 0

75

70§

1 ,7 2 0

1 3 .1 5

3 .6 2

27

2 5 .5 0

8 .1 5

75

70$

1 ,7 1 5

1 3 .5 0

3 .6 8

28

2 5 .7 0

8 .1 0

75

70§

1 ,7 1 5

1 3 .5 5

3 .6 8

29

2 5 .8 0

8 .2 0

75

70§

1 ,7 1 5

1 3 .4 5

3 .6 7

30

2 5 .7 5

9 .1 0

75

70§

1 ,7 2 0

1 2 .5 5

3 .5 4

75

70.554 1 ,7 2 3

A v erag e

2 5 .9 8

T a re

4 .6 0

N et

2 1 .3 8

70§

3 .8 9

4 .2 5 0 53 5 ° R

6 6 .3 0 4 1 ,7 2 3

3 .8 9

15 4 V e lo c ity E q u a tio n ,

o>f b S t a . \ T 1 Pb " ^Tgj.

I 5 8 .9 / s ( Pj^ 3 -)

- I 4 , 8 9 . 9 2 ^555 - n “ V 4 0 12 9 . 6 8 ' 5 2 0 "

VQbs

: 5 8 .9 ( 0 . 3 2 2 ) 3 .8 9

W

; 5 8 .9 y i / E

3

7 3 .8 f . p . s .

= 5 8 . 9 ( 0 . 3 1 6 ) 3 . 8 9 = 7 2 .4 f . p . s .

=0,00238(ifiti)ii§=°-00230 PAV3b s

H .P . ;

3 0 . 0 0 2 3 0 ( 2 . 5 ) ( 7 3 . 8 ) 3 3 2 ,3 1 0

1 I N /5 3 ,8 5 0 3 6 6 . 3 0 ( l , 7 2 3 ) / 5 3 , 8 5 0 = 2 .1 2 h . p . g91

R e s u l t s o f T e s t XX S t a t i c - P l a t e D e f l e c t i o n - 2 1 .3 8 s l o p e - i n c h e s o f a l c o h o l V0 b s .

1

7 3 *8

f .p .s .

vS td . “

7 2 ,4

f* P * s *

SR = 0 .9 9 1 The c a l i b r a t i o n c u r v e s fro m T e s t s XL1 t o XXI i n c l u s i v e m ay b e fo u n d i n C h a p te r 7 1 .

155 TABLE X m

TEST XXI

VELOCITY AND ENERGY RATIO CALIBRATION S p eed Tap 10 B a r o m e te r , 2 9 .6 8 * Hg. P ito t- M a n o m e te r , t a r e h z 2 1 .6 5 , s lo p e 4 /4 0 S t a t i c - P l a t e M an o m eter, t a r e h g z 4 .6 0 T o rq u e B a la n c e T a re © &s I n .A l. Rdg. D a ta

h In .A l. R dg. D a ta

® T h ro a t Temp. OJ* D a ta

© T o rq u e F o rc e o z .R d g D a ta

1

2 8 .0 0

3 .8 5

75

77|

1 790

1 7 .8 0

4 .2 2

2

2 8 .0 0

3 .3 5

75

77f

1 790

1 8 .3 0

4 .2 8

3

2 8 .0 0

3 .1 5

75

77^

1 790

1 8 .5 0

4 .3 0

4

2 7 .9 5

3 .1 5

74

7?1

1 790

1 8 .5 0

4 .3 0

5

2 7 .9 5

3 .3 0

74

77^

1 790

1 8 .3 5

4 .2 8

6

2 7 .9 5

3 .7 0

74

77&

1 785

1 7 .9 5

4 .2 4

7

2 7 .7 0

4 .9 0

74

77

1 785

1 6 .7 5

4 .0 9

8

2 7 .7 0

4 .7 0

74

77

1 790

1 6 .9 5

4 .1 2

9

2 7 .7 0

4 .3 0

74

77

1 780

1 7 .3 5

4 .1 6

10

2 7 .7 0

4 .1 0

74

77

1 785

1 7 .5 5

4 .1 9

11

2 7 .7 0

4 .4 0

74

77

1 785

1 7 .2 5

4 .1 5

12

2 7 .7 0

4 .7 0

75

77

1 780

1 6 .9 5

4 .1 2

13

2 7 .4 5

5 .8 0

74

77

1 785

1 5 .8 5

3 .9 8

14

2 7 .5 0

6 .0 5

74

77

1 785

1 5 .6 5

3 .9 6

15

2 7 .4 0

5 .6 5

74

77

1 785

1 6 .0 0

4 .0 0

16

2 7 .5 0

5 .3 5

74

77

1 785

1 6 .3 0

4 .0 4

17

2 7 .6 0

5 .2 5

74

77

1 785

1 6 .4 0

4 .0 5

18

2 7 .6 0

5 .2 5

74

77

1 785

1 6 .4 0

4 .0 5

T est P o s itio n D a ta

® R .P .M . •

D a ta

® h D e f l. I n .A l. 2 1 .6 5 -®

i/E " xXST

156 TABLE XXXI ( c o n tin u e d )

D a ta

£ : F f C T V O / y'P fy H p a M r J y jr jr

[

w , //Z C S Z F J

S < T A i.F -F O l£ J>/Z £ X

A '& k ' /& . ;s> + s>

J £ £ F O t3 T Y M P A A W J f r /x /F # \ y m * /^ /r? £ '& n? t f f S lA D F j. F t& L

X - i.._

t

'