Aerodynamic Coefficients and Pressure Distribution of Solid Flat and Ringslot Models in...

8/10/2019 Aerodynamic Coefficients and Pressure Distribution of Solid Flat and Ringslot Models in Onedimensional Velocity Gr

1/90

AFFDL- TR- 72- 113

A E R O D Y N A M I C C OE F F IC IE N T S A N D P R E S SU R E

D I S T R I B U T I O N O F S O L I D FL AT A N D R I N G S L O T

M O D E L S I N O N E D I M E N S I O N A L

V E L O C I T Y G R A D I E N T S

H. G. HEINRICH

R. A. NOREE N

J. N. DALE

UNIVERSITY OF MINNESO TA

T E CH N IC A L R E P OR T A F F D L - T R - 7 2 - 1 1 3

D E C E M B E R 1 9 7 3

A ppro ved fo r pub l i c r e l eas e ; d i s t r ibu t ion un l imi ted .

A I R F O R C E F L I G H T D Y N A M I C S L A B O R A T O R Y

A I R F O R C E S Y S T E M S C O M M A N D

W R I G H T - P A T T E R S O N A IR F O R C E B A S E O H I O 4 5 4 3 3


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3/90

A E R O D Y N A M I C C OE F F IC IE N T S A N D P R E SS U R E

D I S T R I B U T I O N O F S O L I D FL A T A N D R I N G S L O T

M O D E L S IN O N E D I M E N S I O N A L

V E L O C I T Y G R A D I E N T S

H. G. HEINRICH

R. A. NOREEN

J. N. DALE

UNIVERSITY OF MINNESOTA

A pproved fo r pub l i c r e l eas e ; d i s t r ibu t ion un l imi ted .


4/90

1973

FOREWORD

Thi s r epor t was pr epar ed i n t he Depar t ment of

Aer ospace Engi neer i ng and Mechani cs of t he Uni ver s i t y of

Mi nnesot a i n compl i ance wi t h U. S. A i r For ce Cont r ac t No .

F33615- 68- C- 1227, " Theor et i cal Depl oyabl e Aer odynam c

Decel er at or I nvest i gat i ons , " Task 606503, " Par achut e Aer o-

dynam cs and St r uct ur es, " Pro j ect 6065, " Per f or mance and

Des i gn of Depl oyabl e Aer odynam c Dece l e rat or s . " The ana l ys i s

pr esent ed i n t hi s r epor t was per f or med bet ween 2 Febr uar y

1970 and 31 J ul y 1972.

The st udy was s ponsor ed j oi nt l y by U. S. Ar my Nat i ck

Labor at or i es , Depar t ment of t he Ar my, and Ai r For ce Syst ems

Command, Depar t ment of t he Ai r For ce, and adm ni st er ed under

t he di r ec t i on of t he Recover y and Cr ew St at i on Br anch, Ai r

F or c e F l i ght Dynam c s Labora t o ry , Wr i ght - Pa t t er son Ai r F or c e

Base, Ohi o, wi t h Mr . J ames H. DeWeese, AFFDL/ FER, as Pr o j ect

Engi neer .

The st udy was accompl i shed i n cooper at i on wi t h

Mr . Thomas R. Hekt ner and sever al st udent s of Aer ospace

Engi neer i ng at t he Uni ver s i t y of Mi nneso t a . Mr . Edwar d J .

Gi ebut owsk i , U. S. Ar my Nat i c k Labora t o r i es , par t i c i pat ed

i n t hi s s t udy by pr ov i di ng val uabl e gui danc e and i dent i f i -

c at i on o f t he pr i nc i pal r equi r ement s .

Thi s r epor t was subm t t ed by t he aut hors i n

August 1972.

Thi s t echni cal r epor t has been r ev i ewed and i s

appr oved.

RUDI J . BERNDT

Act ' g Chi e f , Recover y & Cr ew St at i on Br anch

Ai r F or c e F l i ght Dynam c s L abor at or y

i i


5/90

ABSTRACT

_ The r esu l t s of wi nd t unnel s t udi es of t he aer o-

dynam c_c har ac t e r i s t i c s o f s ol i d f l at and r i ngs l ot par ac hut e

model s i n f l ow wi t h s ever al l i near o ne- di mens i onal d y 2 c

S e S r s

8

^ ? ^ ar e pr es ent ed. The model h S d n S i S S

di amet ers of about 16 i n. Gr adi ent s of 0% 107, 207 and

40% of c ent er l i ne dynam c p r es s ur e per f oot wi t h c e n t e Si n e

t h e t e s t s

S

1 u S J l '

8 8 6 M d 9

f t /

"

c We r e

e a t S l l S d f S "

t est s Sur f ace pr ess ur e measur ement s wer e made on r i ei d

porous mode l s , and dr ag coe f f i c i ent s obt ai ned by i nt egr at i on

of t he pr essur e di s t r i but i on. Aer odynam c f or ce aSd momen?

S S S b S - S j e S "

d e t 6 r mi n e d

* > . meas ur ement s c T '

iii

LINDA HALL LIBRARY

K i r m i

G ,

M.


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TABLE OF CONTENTS

Sec t i on

p a g e

I . I nt r o duct i on

I I . Dynam c Pr essur e Gr adi ent s . 2

I I I . Pr essur e Di s t r i but i on Measur ement s 12

A. Pr essur e Di s t r i but i on Model s 12

B. W nd Tunnel Test s 12

C. Resu l t s 16

I V. For ce Measur ement s 29

A. Par achut es Model s 29

B. W nd Tunnel Test Appar at us 29

C. Coef f i c i ent s 3 3

D. Resul t s 36

V. F r ee Suspensi on Test s

5 7

Appendi x I - Met hod of Pr essure I nt egr at i on 58

Appendi x I I - Tabul at ed Pr essur e Coef f i c i ent s 61

Ref er ences . . . . . 71

v


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I LL USTRATI ONS

FI GURE

PAGE

Rod Assembl y f or P roduc t i on of Ve l oci t y

Gr adi ent i n a 54 x 38 I nch W nd Tunnel

Test Sect i on 3

2

- Dynam c Pr essure vs Di s t ance at Var i ous

Gr adi ent s , Cent er l i ne P r essur e of

4. 0 and 9. 0 psf 4

3. Si de Vi ew of W nd Tunnel Test Sec t i on

Showi ng Rake and Par achut e Model Locat i ons

used i n Pr essure Gr adi ent Measur ement s . . . 5

Measur ed and Desi r ed Pr essur e Gr adi ent f or

G = 0. 1, q = 4. 0 psf

6


- U. l , q = 9. 0 psf . . . ,

7


o - 0. 2, q = 4. 0 ps f

g


0 - U. 2, q = 9. 0 psf

9

4.

5.

6


h

~ q = 4. 0 psf

1 0


G - 0. 4, q - 9. 0 ps f

n

8.

9.

10. Pr essur e Model s

,

0

13

Geomet r y of Pr essur e Measur ement Model s . . 14

S n S f

1

?

1 1

f P r e s s u r e

Tap Locat i ons and

Mode of Pr esent at i on .

15

13. Pr es s ur e Di s t r i but i on on a Sol i d Fl atPar ac hut e Model i n Uni f or m F l ow

1 7

JL /

14. Pr es s ur e Di s t r i but i on on a Sol i d F l at

Par achut e Model f or G = 0. 1, q f 4. O ps f . .

1 8

15. Pr es s ur e Di s t r i but i on on a Sol i d Fl at

Par achut e Model f or G = 0. 1, q = psf . .

1 9

vi


9/90

I LLUSTRATI ONS ( CONTD. )

FI GURE PAGE

16. Pr essur e Di s t r i but i on on a Sol i d F l at

Par achut e Model f or G = 0. 4, q = 4. 0 psf . . 20

17. Pr essur e Di s t r i but i on on a Sol i d Fl at


18. Pr essur e Di s t r i but i on on a Ri ngs l ot

Par achut e Model i n Uni f orm Fl ow 22









23. Ri ngs l ot Model I ns t al l ed i n t he W nd Tunnel . 31

24. W nd Tunnel Appar at us f or Par achut e

For ce Measur ement s 32

25. Vent Nor mal For ce Sensor 34

26. Coor di nat e Syst em of t he Aer odynam c

Coef f i c i ent s

3 5

27. Tangent For ce Coef f i c i ent s f or t he Sol i d

Fl at Par achut e Model f or Uni f or m F l ow

and G = 0. 1 3 7

28. Tangent For ce Coef f i c i ent s f or t he Sol i d

Fl at Par achut e Model f or G = 0. 2

and G = 0. 4 38

29. Nor mal For ce Coef f i c i ent s f or t he Sol i d

F l at Par achut e Model f or Uni f or m F l ow

and G = 0. 1 39

30. Nor mal For ce Coef f i c i ent s f or t he Sol i d

Fl at Par achut e Model f or G = 0. 2

and G = 0. 4 40

v i i


10/90


FI GURE

PAGE

31. Moment Coef f i c i ent s f or t he Sol i d F l at

Par achut e Model f or Uni f or m Fl ow

and G = 0. 1 ^

32. Moment Coef f i c i ent s f or t he Sol i d F l at

Par achut e Model f or G = 0. 2 and G = 0. 4 . 4 3

33. Tangent For ce Coef f i c i ent s f or t he

Ri ngs l ot Par achut e Model f or Uni f or m Fl ow

and G = 0. 1 ^

34. Tangent For ce Coef f i c i ent s f or t he

Ri ngsl ot Par achut e Model f or G = 0 2

and G = 0. 4 \

4 5

35. Nor mal For ce Coef f i c i ent s f or t he

Ri ngs l ot Par achut e Model f or Uni f or m Fl ow

and G = 0. 1

36. Nor mal For ce Coef f i c i ent s f or t he

Ri ngsl ot Par achut e Model f or G = 0

and G = 0. 4 . .

47

37. Moment Coef f i c i ent s f or t he Ri ngs l ot

Par achut e Model f or Uni f orm Fl ow

a n d G

- 0 -

1

38. Moment Coef f i c i ent s f or t he Ri ngsl ot

Par achut e Model f or G = 0. 2 and G =0 . 4 . .

49

Rat i o of C

T

at oC = 0 i n Gr adi ent F l ow

t o C

T

at 0L= 0 i n Uni f or m Fl ow vs Gr adi ent .

St abl e Angl es of At t ack f or t he Sol i d

Fl at Par achut e Model ^

St abl e Angl es of At t ack f or t he Ri ngs l ot

Par achut e Model

s i O C

53

40.

41.

51

42. Rat i o of dC / d * at ^ i n Gr adi ent Fl ow

t o dC / d c


11/90

q

V

q + 0.2q x

4.0 psf

6 0 f ps

0.2 0.4

x

/w

Fig 6 Measured and Desired Pressure

Gradient for G =

0.2,

q =4.0 psf

RAKE POSIT IONS

o 1

2

1.4 a 3

4

o 5

v 6

8


12/90

1.6

RAKE POSIT IONS

Fig 5 Measured and Desired P ressure

Gradient for 0= 0.1,q=9.0psf


13/90

F ig 4 Measured and Des ired P ressure

G radient for G = 0.1,q = 4.0psf

6


14/90

00

z

O

LUt

^00

< o

q:cl

vt- C\J OJ


15/90

-2.0 -1.0 0 1 .0

x ( f t )

2.0

Fig 2 Dynamic Pressure vs Distance

at Various Gradients, C enterline

Pressures of 4.0 and 9.0psf

4


16/90

3


17/90

I I . DYNAMI C PRESSURE GRADI ENTS

A r ev i ew of t he avai l abl e l i t er at ur e showed t hat

t he met hod f or pr oduc i ng a vel oc i t y gr adi ent pr esent ed i n

Rexs 5 and 6 was best s ui t ed f or t hi s st udy. The r ef er enced

met hod was t o pl ace cy l i nd i ca l r ods spanni ng t he f l ow upst r eam

of t he t est ar ea and t o var y t he spaci ng bet ween t he r ods

I n order t o devel op a vel oci t y gr adi ent acr oss t he wi nd t unnel

t es t sec t i on, t he spac i ng woul d be wi de on t he hi gh vel oci t y

s i de and nar r ow on t he l ow vel oc i t y s i de. Ref er ences 5 and 6

gave met hods t o cal cul a t e an i ni t i al r od spac i ng t hen by

means of exper i ment s, t he r od spac i ng coul d be modi f i ed unt i l

t he des i r ed gr adi ent was es t abl i shed wi t h sat i s f ac t or y ac c ur ac y.

The det ai l s of t hi s pr oc ess ar e as f ol l ows . A r ow

of ver t i c al s t eel r ods f as t e ned t o al um num r ai l s was i ns t al l ed

at t he ups t r eam edge of t he t es t sec t i on ( Fi g 1) Sl ot t ed

s l eeves at each end of t he r od f i t over t he r ai l s and al l owed

var y i ng t he r od spac i ng ac r oss t he wi nd t unnel . A l i near

vel oc i t y gr adi ent c l osel y appr ox i mat i ng t he des i r ed l i near

dynam c pr essur e gr adi ent was s e l ect ed, and t he met hods of

Ref s 5 and 6 wer e used t o c al c ul at e t he i ni t i al spac i ngs f or

t hi s l i near v el oc i t y gr adi ent . The r ods wer e s et at t hi s

i ni t i a l spac i ng and t he r esu l t ant pr essur e gr adi ent measur ed

The pr essur e di st r i but i on was measur ed wi t h a r ake whi ch

spanned t he t est sect i on. The r ake had 48 t ot a l pr essur e pr obes

and f our s t at i c pr essur e pr obes at i nt er val s of one i nc h.

Af t er t hi s f i r st measur ement , t he number and spac i ng of t he

r ods wer e changed and t he pr essur e di st r i but i on checked. Thi s

pr ocess was r epeat ed unt i l t he des i r ed dynam c pr essure

gr adi ent was es t abl i shed.

r - n n i

I l l

n

t

o

i S

" T n

6

^

t h e f o l l o w

i

n

g gr adi ent s wer e es t abl i shed

/ n ' J * L

a

" '

4 Wl t h

c ent er l i ne dynam c pr essur es of

4. 0 ps f and 9. 0 ps f , r es pec t i vel y. Fi gur e 2 i l l us t r at es t he

numer i c al f or m of t hes e gr adi ent s .

The ar r angement of t he r ods, t he r ake, and t he pos i -

t i on of t he par ac hut e, used i n t he l at er t es t s , i s shown i n

F i g 3. The dat a po i nt s , showi ng t he ac t ual l y es t abl i shed

gr adi ent s , ar e shown i n F i gs 4 t hr ough 9. The l i nes t hr ough

t he dat a po i nt s r epr esent t he des i r ed gr adi ent s . The dat a

poi nt s shown are onl y f or ever y t hi r d pr essur e pr obe on t he

r ake i n t he c ent r a l por t i on of t he t es t s ec t i on. Si mpl e ob-

se rvat i on of t he f l ui d hei ght s i n t he mul t i t ube manomet er

showed t hat t he pr essur es at t he ot her cent r a l pr obe l ocat i ons

f i t t he l i near pr essur e gr adi ent r equi r ement . Out s i de of t he

c ent r al ar ea the vel oc i t i es dec r eased bec ause of wa l l ef f ec t s

and boundar y l ayer s. The f i gur es show t hat t he agr eement

bet ween t he des i r ed and the es t abl i shed gr adi ent s i s sat i s -

f ac t or y i n t he ar ea i n wh i ch t he par achut e mode l wi l l be

l oc at ed.

2


18/90

I NTRODUCTI ON

. , . ,

Th

? ;

s r e

P

r

t pr esent s t he r esul t s of wi nd t unnel

s t udi es of t he aer odynam c c har ac t er i s t i c s of s ol i d f l at and

r i ngs l ot par ac hut e model s i n f l ow wi t h var i ous l i near one-

di mens i ona l dynam c pr essur e pr of i l es c al l ed gr adi ent s . The

si ze o t he model par achut e and t he sl ope of t he gr adi ent s

wer e set so t hey wer e compar abl e t o a par achut e oper at i ng

i n t he wake o f a l ar ge a i r c r a f t ( Ref s 1, 2) . Based on par a-

chut e s i ze , t he gr adi ent s st udi ed wer e much st eeper t han a

t ypi cal a t mospher i c wi nd gr adi ent ( Ref 3) , and not near l y

? r J ^

t h e

5

a d i e n t i n

t he wake of a f or ebody or payl oad

(,Ker The gr adi ent s wer e est abl i shed by var yi ng t he

spaci ng bet ween many t hi n r ods pl aced i n a subsoni c wi nd

t unnel j us t ups t r eam of t he t es t s ec t i on. Cal c ul at i ons gave

an appr oxi mat e i ni t i a l r od spac i ng, and t hen t he gr ad enf s

wer e measur ed and t he spaci ng adj ust ed unt i l t he desi r ed

gr adi ent was obt a i ned. W nd t unnel t est s wer e conduct ed at

p r e s s u r e â t h e cent f -

6

f t

J ?

e C

?

n d 9 0

" / s ec ^ S i ' d ^ l c

pr essur es at t he c ent er l i ne of 4 ps f and 9 ps f , r espec t i vel y

p re ssu re

1

per

S

f oot ?

X

'

1 0 %

'

2

% M d 4

%

f

- nt er l f Se dynl m c

per f or manc e c har ac t er i s t i c s

r

i n t hi s gr a di ent f l o w- pr es s u r e

di st r i but i on measur ement s wer e made on

rigid

c l ot h

covered

T h

n

S

?

t 8 S t S W6 r e ma d e i n u n

i f o r m f l ow, and at t he

s mal l es t and l ar ges t gr adi ent f or eac h c ent er l i ne v el oc i t v

f or c e oef f i c i ent s f nr

nS We r e i n t e

â t e d and e d u c e d " ? '

meas ur ement s ?

f

r c o m

P

a r i s

" wi t h t he r es ul t s of f or c e

Aer odynam c f or c e c oef f i c i ent s , r r and C

wer e measured as f unc t i ons o f angl e o f at t ack f or n m,

f l exi bl e J S i d l S J ' ,

T

^

f

- c e L a s u r e ^ f we ^ â d V wi t ^

Fi nal l y?

lor

a ^ i t a ^ ^ i ^ ^ f ^ J S S f c S J

0

?

1

? "

gr adi ent f l ow, t he model ? wer e f r l e ^ ^ e f a n f o ^ r v e d

1


19/90

di s t ance f r om ax i s of symmet r y t o canopy ski r t

measur ed al ong canopy pr of i l e

nom na l ar ea

s/ s

max

t angent f or ce

c ent er l i ne vel oc i t y

t es t s ec t i on wi dt h, 54 i n

t es t sec t i on wi dt h c oor di nat e

t es t sec t i on hei ght c oor di nat e

par achut e angl e of at t ack

t r i m angl e, s t a bl e angl e of at t ac k, Q, = 0,

dC / dw < 0 T*

s t i f f nes s i ndex ( Ref 9 )

Ot her symbol s, when used, are def i ned i n t he

t ext .

Unl ess spec i f i c al l y expr essed ot her wi se t he

c oef f i c i ent s i ndi c at ed ar e based on nom na l ar ea

x i i


20/90

SYMBOLS

dr ag c oef f i c i ent *

moment coef f i c i ent *

t ot al nor mal f or c e c oef f i c i ent *

pr es s ur e c oef f i c i ent

di f f er ent i al pr es sur e c oef f i c i ent

ext er nal pr es s ur e coef f i c i ent

i nt er nal pr es s ur e c oef f i c i ent

t angent f or c e coef f i c i ent *

nom nal di amet er

gr adi ent par amet er ,

hei ght of t es t s ec t i on,

3

f i

n

aer odynam c moment

t ot al no rmal f or c e

f r ont nor mal f or c e

vent nor mal f orce

f r ees t r eam s t at i c pr e ss ur e

l oc al ext er nal s t at i c pr es s ur e

l ocal i nt er nal s t at i c pr e ss ur e

l oc al dynam c pr essur e

c ent er l i ne dynam c p re ssur e

4. 0 ps f

9. 0 ps f

gr adi ent

l engt h measur ed al ong canopy

p r o f i l e

x i


21/90

TABLES

TABLE

PAGE

I .

Dr a g Coef f i c i ent s f r o m I nt egr at ed

Pr e ss ur e Di s t r i but i ons . .

. 27

I I .

Sol i d Fl at and Ri ngs l o t Par achut e Model s

. 30

I I I .

Pr es s ur e Coef f i c i ent s f or t he Sol i d Fl at

and Ri ngs l ot Model s , Uni f or m F l ow

. 60

I V.


Model , G = 0. 1, q = 4. 0 psf

. 61

V. Pr es s ur e Coef f i c i ent s f or t he Sol i d

F l at Model , G = 0. 1, q = 9. 0 psf

. 62

VI .


Model , G = 0. 4, q = 4. 0 psf .

VI I .


Model , G = 0. 4, q = 9. 0 psf

. 64

VI I I .

Pr es s ur e Coef f i c i ent s f or t he Ri ngs l ot

Model , G = 0. 1, q = 4. 0 ps f . . . . . . .

. 65

I X.


Mode l , G = 0. 1, q = 9. 0 ps f . .

. 66

X.


Model , G = 0. 4, q = 4. 0 ps f . . ? . . . .

. 67

XI .


Model , G = 0. 1, q = 9. 0 ps f . . ?

68

x


22/90


FI GURE PAGE

43. Rat i o of dCj ^ dc*. at

cX

T

i n Gr adi ent F l ow

to dC

M

/ dj X at

DC

_ i n Uni f or m Fl ow f or t he

i x


23/90

-0.2 0 0.2 0.4

x

/

/ W

F ig 7 M eas ured and Desired P ressure

Gradient for G =0.2 , q= 9.0 psf

RAKE POSIT IONS


24/90

RAKE POSIT IONS

o 1

2

A 3

* 4

o 5

v 6

O l

- 0 . 4 - 0 . 2 0

2

0 4 ~ ~

x

/wF ig 9 Measured and Desired P ressure

G radient for G=0.4 ,q

=

9.0 psf

i i


25/90

1.6

1.4

1 2

1.0

0 8

0 6

0.4

0

I

R AK E P OSITIONS i

i

/

/

2

A 3

0- 4

O 5

v 6

I

I

I

/

2

A 3

0- 4

O 5

v 6

I

I

I

t

r

9

2

A 3

0- 4

O 5

v 6

I

1

/

s

/

/

3

r i

I

/

1

1

*

i

1

l

1

q = q + 0.4 qx

q = 9.0 psf

v = 9 0 fp s

/ s

/

11

i

q = q + 0.4 qx

q = 9.0 psf

v = 9 0 fp s

/

/


26/90

I I I . PRESSURE DI STRI BUTI ON MEASUREMENTS

The mai n obj ec t i ve of t hi s s t udy i s , of c our se t he

es t abl i shment of par ac hut e aer odynam c c oef f i c i ent s i n gr adi ent

f l ow. Si nce no publ i cat i on on t hi s subj ec t coul d be f ound

i n t he l i t er at ur e, pr essur e di s t r i but i on measur ement s wer e

made t o pr ovi de a basi s f or checki ng t he measur ed f or ce

c oef f i c i ent s agai ns t t he f undament al pr es s ur e di s t r i but i ons

f r om whi c h t hey der i ve.

A

- Pr es s ur e Di s t r i but i on Model s

The pr ess ur e di st r i but i ons wer e made on r i gi d con-

cave bodi es const r uc t ed of heavy wi r e f r ames wi t h r adi a l

member s f o rm ng c i r cul ar a rcs . The wi r e f r ame

was

cover ed wi t h

h

/ y

- I L - C- 7020 c l ot h ( Ref 7) , and t he model s l ooked

l i ke hem spher es. F i gur e 10 shows t hese model s and F i e 11

shows t hat t he model s had a di amet er of 10 i n and a r oi

of

14 pr essur e t aps al ong a gr eat c i r c l e . One mode l had i nt e rnal

pr essur e taps and t he ot her had ex t er na l pr essur e taps J i t h

i dent i c al t ap l oc at i ons on each model . e ^ur e

c a p s Wl f c h

. . 1 s i mul at e a s ol i d f l at c i r c ul ar par ac hut e model

t he hem spher es wer e c ompl et el y c over ed wi t h t i ght l y f i t t l d

nyl on c l ot h. For s i mul at i on of a r i ngs l ot par af hut e m del

s l ot s were, c ut i nt o t he c l o t h at l oc at i ons shown inF i g11

The cons t ant s l ot wi dt h of 0. 04 i n was set f n

a

I

g

I .

poros i t y o f 4 6% based on t he sur f ace ar a of f he hemf s ph e ' "

Thi s por os i t y f i gur e was sel ec t ed t o mat c h the ge omJ S i c

por os i t y of t he f l exi bl e r i ngs l ot par ac hut e modf l

B* W nd Tunnel Test s

axi al s t i

n

r a n r i

r

h f l T %

d i S t r i b U

^

0 n m

d e l s w e r e

r un t e d on an

axi al s t i ng and hel d at z er o angl e of a t t ac k. The s t i n?

and suppor t syst em wer e t he same as descr i bed

l a K r

f ^t h e

f a r c

?

measur ement s. The model pr essur e t aps we?e i ni ? i a l l v

t hr ee t i mes W t h ^ * *

8 t l n

^ J n S me n L

cnr ee c i mes W t h a r ow of pr essur e t aps, bot h above anH

d l l T i n

c e n t e r

pl ane, t hi s

P

? J c e 3 S e gf ves pr es s ur e

dat a i n 45 i nc r ement s over t he who l e sur f ace nf t h f v , u

For uni f or m f l ow, one may assume that the p r e s s u r e d i s S bS t f '

i s ax i symmet r i c , and the r esu l t s nf

a

i i i di s t r i but i on

' T ^ r F I " t he gr adi ent f l ow i L ^ e S e ^ i K r ^ S o n " "

6

'

s houl d be s ymmet r i c about t he hor i z ont al p l a n e t e S L

gsrgs i s ^^u

^ w V ? ^

1

were tested? S f S ^ S ^ ^ t J ' V ? - ^ ^

12


27/90

;

r /

TTrXL


28/90

CD

Z

C

CH

O

Ll

00

Z

o

*

V

O

O

oo


29/90


30/90

G - 0. 4 f or bot h c ent er l i ne dynam c pr es s ur es . I nt er nal and

ext er nal pr essur es wer e measur ed usi ng a mul t i t ube manomet er .

C. Res ul t s

Al l of t he i ndi vi dual pr es s ur e c oef f i c i ent s ar e

shown i n F i gs 13 t hr ough 22 and ar e t abul at ed i n t he Appendi x.

The pr essur e coef f i c i ent s shown ar e based on cent er -

l i ne dynam c pr essu re ,

C

n

= C - C

P

d Pi P

On t he f i gur es t he +s * di r ec t i on i s i nt o t he hi gher vel oc i t y

f ol l ow ^ " " V

a n d

t he r ot at i on angl es i ndi c at ed

Y

f o l l ow F i g 12. These f i gur es show t hat t he pr i mar y ef f ec t

of t he gr adi ent i s t o r educe t he magni t udes of t he pressur es

Thi s i s par t i cul ar l y not i c eabl e i n

the

di f f er ent i al

P

pr l s s ur e

C

p

d

'

e 1 S mo r e r e d

u c t i o n wi t h s t eeper gr a di ent s ^

m "r ange

i n

Pr es sur e di s t r i but i on f r om t he l ef t

t o t he r i ght s i de i s qui t e s mal l . On t he s ol i d f l at par ac hut e

t her e appear s t o be a r eoccur r i ng unsymmet r y of C measur ed

at t ap l ocat i ons of 0 and 180 . Ot her unsymmet r i es ar e so

smal l t hat t hey ar e not t r aceabl e wi t h any degr ee of cer t a i nt y

On t he r i ngsl ot par achut e no unsymmet r i es can be det ect ed

One may assume t hat t he canopy s l ot s equal i ze t he S e s s S e s

t o t he ex t ent t hat no unsymmet r i es ex i s t or ar e L S smal l t o

be r ecor ded by t he exper i ment al met hod us ed.

The dr ag c oef f i c i ent s obt ai ned by i nt egr at i ng t he

pr es sur es ar e s hown i n Tabl e I . For t he u n i f o mf l o w E d i t i o n s

t he aver aged pr essur e di s t r i but i on was i nt egr at ed f or "

d l t l o n s

gr adi ent f l ow t he i ndi v i dual pr essur es obt ai ned at t he angul ar

of

S

t he c i r c ul ar

U

f l at

8 h

T

t h a t t h e

^a g' c o e f f S f e n? s

and t he r i ngs l ot par ac hut e ar e s i gni f i -

c ant l y smal l er i n gr adi ent f l ow and dec r ease as t he s t f eni t h

of t he gr adi ent i nc r e as es . s t r engt n

16


31/90

1.6

A

A

A

1

A

A A

A

C p

A

A

\ A

A

L

c

P d

O

D O

o c

o

0.8

o

O

O 1

D O

O c

c

P i

q =4, 9p s f AVER AGE D

r\ / i

0

-0.

8

-0.4

0

0.4

.0.8

s

0.4

a

n -

3

D

c

0.4

a

-J U

u

t

P e

J -0 .8

Fig 13 Pressure Distribution on a

Solid R at Parachute Model

in Uniform Flow

17


32/90

R g 1 4

^

r

f f

u r e

D is tribution on a

f o T

G

F

% / p ^ %

f

M o d e l

8


33/90

o

I.D

2

\

0

r 2

C p

a S

a a

2

H

c

P d

0

r 2

C p

o

0

1

n r

O

S 6

0

6

a a

1

C

P ;

O

- 180

0.4

A - 135 ,2 25

9 0 \ 2 7 0

0

O - 0

a - 45 ,315

a - 9 0 , 27 0

-0.8

- 0 4

0

0.4

0.8

-HA

8

J a

A a

e

*

6

a 6

a 4

a

-0.8

C

P e

F ig 15 P res sure Distribution on a

Solid F lat P arachu te Model

for G = 0.1

j

q = 9psf

19


34/90


Solid F lat P arachute M odel

for G = 0 .4 , q =

4

psf

20


35/90

1

.6

o

1.2

ft

C

P

0.8

0

8

8

6

1.2

ft

C

P

0.8

1

a

a

e>

a 2

c

1.2

ft

C

P

0.8

O

0

XT

R S

a 8 a

6

1.2

ft

C

P

0.8

a

i

^ 8

o o

A

A

s

o - 180

0.4

A 135

J

2 2 ^

- 9 0 ,270

o - 0

a 45 ,315

D

- 9Cf ,270

-0.8

OA

0

0.4 0.8

o

A

o

Q

2 9

4 O

fi

1

H

8

s

n

ci

A *

-0.8

C

P e

F ig 17 P ressure D is tribution on a

Solid F lat P arac hute Model

fo r 6=0 .4

j

q = 9psf

21


36/90

F ig 18 P ressure D is tribu tion on a

R ingslot P a ra c hu te M o d e l

in U niform F low

22


37/90


Ringslot Parachute Model

for G = 0.1, q" = 4 psf

23


38/90

F ig 2 0 P ress ure D is tribution on a

f

R

7

s , o t

Q i

P a r

f

hute

p

M o

d e

,

24


39/90

&

o c

o

A

D

E

0

a 1 2

C

P

^0.8

ft '

* ft

0

a 1 2

C

P

^0.8

C

P d

a

0

a 1 2

C

P

^0.8

-

O

b o

O c

A

O

A

D

t f t

8 a

a

0

a 1 2

C

P

^0.8

A

b a

3 c

CP,

o - 180

0.4

A - 135 ,225

- 90 ,270

0

o - Cf

a - 45 ,315

- 9 tf , Z 7 0

-0.8

-0.4

0

0.4

S* 0.8

&

0.4

6 d

&

0.4

8

i

1 &

ft t

ft

-0.8

C P E

F ig 21 P res sure Distribution on a

R ingslot P arachute Mode

for G = 0.4 , q = 4 psf

25


40/90

F ig 22 P ress ure D istribution on a

R ingslot P arachute Mode

for G =0.4 , q = 9 ps f

26


41/90

o

Id

cr

O

u

f -

z

2

O i n

Ld

^ O

a f e

n

icr

i

no

O

O

a>

n

icr

i n

m

LO

Aerodynamic Coefficients and Pressure Distribution of Solid Flat and Ringslot Models in...

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Transcript of Aerodynamic Coefficients and Pressure Distribution of Solid Flat and Ringslot Models in...