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WIND-PUB>TEL TESTS 03' I M E 1J.P.C.AI 45-125 AIRFOIL , & THICK Af'RFOIli FOR HIGH-SBBBD A-I-BPLAfEfS .
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I n v e s t i g a t i o n s of t h e p r e s s u r e d i s t r i b u t i o a , t h e 2 r o f i l e d r a g , grid -.%be. l o c a t i o n of t r a n s i t i o n f o r 8 30- inch-ohord 26-p'ercent-thi ck B .A,C . A . -45-125 a i r f o i l were made i n t h e IT.$+C'.A.. 8 - f o o t high-speed 'wind t u n n e l f o r t h e p u r p o s e of ai'ding i n t h e development o f . & t h i c k wing f o r high-spaed: a i r p l a n e s . The . t e s t s -were lnabe at a l i f t c o e f f icieizf of , 0 . 1 . f o r Humbers from 1;750,,000 t o 8 , 6 9 0 , 0 0 0 , cor're.s'ponding t o - s p e e d s f 2 . o ~ 80 . t o 440 m i l e s r - peP h o u r &t 59O F,. 'The e f e e c t on t h e p r o f i l e d r a g af 1Jq f i x i n g the t r a n s i t i o n . p o i n t was a l s o 2 n v e s t i g a t e d .
a553 . !J!h& e f f e a t of . c o n p r e s s i b i l i t y on :the r a t e of 1 reas-e of p r e s s u r e coe.ffi'c:ients was found t o Be g r e a t e r t h a ~ t h a t p r e d i c t e d b v :a: s i m p l i f i e d t h e o r e t i d a l e x p r e s s i o n f o r thin: wings. The r . e s u l t s i n d i c a t e d t h a t , f o r a l i f t coef-.
f i ~ i e n t of 0.1, t h e c r i t i c a l s p e e d of t h e Z.A.C,A. 45612'B . a i r f o i l was about; 460 l r i l e s p e r h o u r a t 5g0 F,.
The v a l u e of t h e p r o f i l e - d r a g c o e f f i c i e n t a t a Beynolds Number of 4 , 5 0 0 , 0 0 0 was 0.0058, o r a b o u t h a l f a s l a r g e a s t h e v a l u e f o r t b e lJ.A,G,Ar. 0025 a i r f o i l . The i n c r e a s e i n t h e p r o f i l e - d r a g ' c o e f f i c i e n t f o r a g i v e n movement of t h e t r a n s i t i o n p o i n t was a b o u t t h r e e t i m e s as l a r g e as t h e o-oqresponding i i l c r a a s e for. t h e N . A . C , b . . 0012 a i r f o i l . 5faqsi'i.ion d e t e r m i n a t i o n s I n d , i c a t e d t h a t , % o r h i d Reynolds ~ u m b a r s u p t o '?,000,000, l a m i n a r boundary 1ayePS were m a i n t a i n e d o v e r a p p r o x i m a t e l y 40 p e r c e n t . of t h e . u ~ ~
p e r and t h e l o w e r s u r f a c e s of t h e a i r f o i l 2 & ? . - _ _ _ + & @
INTRODUCTION
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'iQ"r+'d 1 7 The minim, s t a t i c . p r e s s u r e on a n f o i l h a s :en u s e d a @ a n ' i n d e z , of , t h e c r i t i c a l s p e e d of t h a t a i r f o i l , a h i g h minimum p r e s s u r e i n d i c a t i n g a l o w c x i t i c a l s p e e d .
( s e e r e f e r e n c e 1 4 ) Most c o n v e n t i o n a l a i r f o i l s have h i g h p e a k s 109 minimwn'pressure t h a t e x t e n d o v e r o n l y a small p a r t 02 t h e c h o r d . I t s h o u l d b e p o s s i b l e t o produce a i r - f o i l s h a v i n g h i g h c r i t i c a l s 2 e e d s by c h a n g i n g t h e h i g h p r e s s u r e peaks t o a f l $ t p r e s s u r e d i s t r i b u t i o n w i t h t h e minimum p r e s s u r e s e x t e n d i n g o v e r a l a r g e r p o r t i o n of t h e s i r f n i l .
Thick wings a r c d e s i r a b l e f o r man:=T a g p l i c n t i o . n s , such a s engine-in-wing i n s t a l l a t i o n s , f u e l s t o r a g e , and r e c e s s e s f o r l a n d i i ~ g g e a r o r o t h e r e q u i p n e n t . Thick wings of coil- v a n t i o n a l d e s i g n , however, have 1 0 ~ 1 c r i t i c a l s p e e d s and cr2 i n e f f i c i e n t f o r u s e a t h i g h s p e e d s . A 2 5 - p e r c e n t - t h i c k a i r f o i l w a s d e s i g n e d h a v i n g n p r e s s d r c d i s t ~ i b u t i o n i n t e o d - ed t o g i v e c h i g h c r i t i c a l s p e e d f o r s wing of t h i s t h i c k - n e s s .
/' .This ~ z i r f o i l ~ w a s t e s t e d t o d e t e r m i n e i t s c r i t i c c l s p e e d and t o o b t a i n dakn t . o a i d , i n t h e d e s i g n of o t h e r t h i c k wings w i t h h i g h c r i t i c a l spcods... Tho t e s t s ware made i n t h e 8 - f o o t high-speed wind t u n n e l a t a l i f t c o e f - f i c i e n t of 0.1 and a t s p e e d s r a n g i n g from 80 t o 440 m i l e s p e r hour, The r a n g e of t h e t e s t Roynolds.l\iumber was 1 , 7 5 0 , 0 0 0 t o 8 , 6 0 0 , 0 0 0 , b s s o d on t h e 30-inch chord. . Com- p l e t e p r o s s u r c - d i s t r i b u t i o n and d r a g d c t c r r n i n a t i o n s were mado t o obt;:,in s e c t i o n c o o f f i c i c n t s . The l o c a t i o n of t h o t r a n s i t i o n p o i n t was d e t e r m i n e d a l o n g b o t h s u r f a c e s of tlic a i r f o i l t h r o u g h o u t t h e spccd. r a n g e , Th.c method of t h e s u r f a c e p i t o t was u s e d a s s e v e r a l p o s i t i o n s a l o n g t h o c h o r d t o d a t o r ~ i n c t h e l o c a t i o n of t h e t r a n s i t i o n p o i n t , t h e p o i o t a t which t h e - vo1ocit:r a c n r t h e s u r f a c e o f - t h e wing s t a r t c d 40- i n c r e a s e v e r y r a p i d l y b e c a u s e o f . tlxe o n s e t of t u r b u l e n t flow. For some t e s t s , t r n n s i t i o n w a s n r t i f i c i 8 ? . l - l y f Fxcd .?,t two chord l o c a t i o n s .
*L139 APPARATUS AMD METHOD mk4;;. I 7-t. r u m r 3 g ~ " n ~ v du.r-*Arm+,$ Ipr itt.
-6.' & P P J + ~ ~ - i w m a " * - & P . & Z + $ ---*a - 4 * The' i n v e s t i g a t i o n w a s made i n t h e 1T,A.C .-A,. 8-f oot high-spbed wind t u n n e l , a s i n g l e - r e t u r n c l o s e d - t h r b a t t u n n e l of c i r c u l a r c r o s s r;ectSon.- Sphere t e s t s i n t h i s t u n n e l have shown v i r t u a l l y t h e same c r i t i c a l Reynolds Number a s i n f r e e a i r ( r e f e r e n c e 2 ) .
- - The 3 f . B . C . A . 45-125 a i r f o i l was u s e d i n t h e t e s t s , ( s e e t a b l e I . ) The f i r s t . d i g i t , 4 , of t h e a i r f o i l d e s i g - n a t i o n i n d i c a t e s t h o c l a s s of a i r f o i l t h a t h a s a f l a t - t o p # . - - p r e s s u r e d i s t r i b u t i o n , a uniform d i s t r i b u t i o n of l i f t --%- a l o n g t h e c h o r d a t t h e d e s i g n l i f t c o e f f i c i e n t , and a cusped- t r a i l i n g edge. The second d i g i t , 5 , d e s i g n a t e s t h e 'approximate - g o s i t i o n a t which t h e a d v e r s e p r e s s u r e g r a d i e n t b e g i n s , 50 p e r c e n t of t h e c h o r d . The f i r s t d i g i t of t h e l a s t t h r e e numbers r e p r e s e n t s t h e d e s i g n l i f t c o - ' e f f i c i e n t , 0.1, and t h e l a s t two d i g i t s g i v e t h e maximum t h i c k n e s s , 25 p e r c e n t of t h e chord.
The z i r f o i l had a 30-inch c h o r d . The s u r f a c e was p a i ~ t e b and t h e n sanded w i t h 110. 500 w a t e r s a n d p a p e r ui- ti1 i t was a e r o d y n ~ m i c a l l y smooth.
The a i r f o i l c o m p l c t e l ~ spanned. t h e t u n n e l and was f s s t 4 n c d d i r o c t l y t o t h a t u n n e l w e 1 1 ( f i g . 1 ) . Two- d i m e n s i o n a l f l o w i s approximated w i t h t h i s sct-up. The p r c s s u r c s were measured a t 31 p r a s s a r e ' o r i f l c e s c o n n e c t - ed t o a p h o t o g r a p h i c a l l y r e c o r d i n g m u l t i n l c - t u b e manom- d t e r . The o r i f i c c . ~ v e r e s t a g g e r e d s o t h a t no o r i . f i c e was i n t h e wake of o t h e r o r i f i c e s ; t h e y were s o l o c a t e d from t h e c e a t e r of t h e span t h a t t h e s u r v e y r a k e was n o t i n t h e vra!ro o f a a y o r i f i c e s .
. .
The d r a g of the' a i r f o i l w a s determine$- from measure- ments i n t h e wake u s i n g J o n e s ' method ( r e f e r e n c e 3 ) modi- f i e d t o i n c l u d e t h e e f f e c t s of c o m p r e s s i b i l i t y . Measure- ments v e r e made w i t h a s u r v e y r a k e s u p p o r t e d by a v e r t i - c a l s t r u t and l o c a t e d oue-half c h o r d l e n g t h behind t h e t r a A l i n g edge of t h e wing. The r a k e c o n s i s t e d of 25 e q u a l l y s p a c e d t o t a l - p r o o s u r e t u b e s a n d 6 s t a t i c - p r e s s u r e - t u b e s . .TBe p r e s s u r e r e a d i n g s w e r s p h o t o g r a p h i c a l l y r e - c o r d e d on a mu-ltiple-tube manometer.
*) Poy some t e s t s t h e t r a n s i t i o n p o i n t was f i x o d a t 15 and 30 p e r c e n t o f thc c h o r d from t h e ].cadins edge by a 1 / 4 - i n c h s ~ a n v i s e . s t r i p of 0,023-inch carborundum g r a i n s s e c u r e d t o b o t h s u r f a c e s w i t h t h i n s h e l l a c . The 0.023- i n c h g r a i n s were u s e d b e c a u s e , 211 a p r e l i m i n a r y t e s t , 0.0037-inch carborundun g r a i n s f a i l e d t o p r o d u c e t r a n s i - t i o n . The f a i l u r e of t h e narrow band of 0.0037-inch g r a i n s t o p r o d u c e t r a n s i t i o n i s no i n d i c a t i o n of t h e p e r - m i s s i b l e r o u g h n e s s f o r t h i s wing. P r e s s u - r e d i s t r i b u t i o n , d r a g , and t r a n s i f ion-z)oint L o c a t i o n v e r e s e p a r a t e l y de- t e r m i a e d . S u r f a c a p i t o t t a b e s were a l s o u s e d t o make c e r - t a i n t h a t t r a n s i t i o n had o c c u r r e 6 a t t h e cnrborundum s t r i p s .
--v a - E .
SYI'ISOLS I A - - v L * ' [ w w i i , r C b , f f i i G + + & z y , . r - - . - The s:mbol%> u s e d i n t L i s , r s p o r t a r e d o f iile% a s f o l - lows: V , s i r s p e e d .
I$, ld'iach nu~cber, % h a r a t i o of t h e a i r speed t o t h e s x ~ e e d of sound i n a i r a t t h e t e n p e r a t u r e o f t h o t a s t s , G , w i ~ l g c h o r d .
x , d i s t a n c e measurcd from l e a d i n g edge a l o n g c h o r d of wing.
13, Royaolds Bumber b a s e d H, t o t a l p r e s s u r e .
p l o c a l s t a t i c p r o s s u r e on t h e a i r f o i l .
q , dynamic p r e s s u r a of t h o a i r s t r e a m (1/2 p ~ 2 ) .
S,. p r e s s u r e c o o f f i c i o n t (7).
S o , v a l n o of S z t M = 0 .
S c r , p r c s s u r e o o e f f i c i c n t a t which t h o speod of sound i s r e n c h o d . a t somo p o i n t on t h o a i r f o i l .
M c r , I k c h 'number c o r r c s g o n d i i i g t o Scr.
a, a n g l e o f a t t a c k o f a i r f o i l .
- m.5: c,, , s e c t i o n L i f t c o c f f i c ? - e n % .
a d o , s O c t i o i i p r o f ile-dreg . c o ~ f f i c i c n t .
RESULTS The p r c s s u r c d i s t r i b u t i o n s on b o t h s u s f n c c s of t h c a i r f o i l f o r cl = C . 1 (a = 00) a r c shown i n f i g u r e 2
f o r v a r i o u s vn1u.z~ of . F i g u r c 3 sho::~s c o m p ~ i r i s o n s he-
twaen t h o o x p ~ ? ? i . ~ . ; o i l t s l v n r i c t i o i i t ~ i t h s r e o d of t h ~ p r c s - s u r a coefficient f o r t h a a i r f o i l t o s t o d aad B c k c r e t ! s the- o r o t i c ; ? , l v n r i c t i o n f o r t h i n a i r f o i l s ( r c f c r o n c o 4 ) as 1 - S ,
g i v c n by t h c f a c t o r I - . Tho c o l n ~ u t o d p r o ~ s u - ~ e o
on f h c a p p o r s u r f a c e of t h e i T . d . C . A . 0025 a i r f o i l & r c c o n p ~ . r o d i i ~ f i g u r c 4 w i t h t h z mc2,surcd p r e s s u r e s oa t h c B . A . C . B . 45-125 f o r n liZt c o c f f i c i 2 n t of 0 . 1 at l o w spccd-.
T11o v n r i c t i o n of tire Rcpnolcls Zun33cr w i t h Mach num- b o r i s shoyrn i n f i g u r o 5. I n f i g a r c 6 , t h e l o c a t i o n of t h e -& - .--
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t r a n s i t i o n p o i n t i s shovrn f o p v 2 r i o u s v n l u z s of t h c ' Rcyaolds Number. Curves of c d o f o r , t h c v a r i o u s s u r f n c o c o n d i t i o n s a r e shown i n f i g u r e 7 ; i n a d d i t i o n , c u r v e s of f o r t h c B.A.C.A. 0025 a i r f o i l ( r o f o r c u c c 5) and t h c cd0 l n n i n c r and t u r b u l e n t s k i n - f r i c t i o n c u r v e s f o r f l a t - p l z t e s a r e shown. Z'igurc 8 shows t h e v z r i c t i o n o f cdo w i t h t h e t r a n s i t i o n - p o i n t l o c a t i o n f o r v a r i o u s Reynolds Burnbers.
A l l t c s t s r e p o r t e d h e r e i n were made w i t h t h e a i r f o i l .
a t aa a n g l c of q t t a c k of 0°, which gave a p p r o x i m a t e l y t h e d e s i g n l i f t c o e f f i c i e a t of 0.1. In t h e t e s t s w i t h rough- n e s s a t 0.15c, however, a l o s s i n l i f t o c c u r r e d at h i g h s p e c d , p r o b a b l y b e c a u s e of t u r b u l e n t s e p a r a t i o n .
Innsmucl~ a s tho wing was t h i c k r e l a t i v e ' t o t h e t u n - n e l d i a m e t e r , a c o r r e c t i o n f o r c o n s t r i c t i o n was mul..e t o t h e p r e s s u r e coefficients and t o the' p r o f i l e - d r a g c o e f - f i c i e n t s . T h i s o o r r e c t i o n v a r i e d from 2 p e r c e n t a t low s p e e d s t o 5 p e r c e n t . a t h i g h s p e e d s . A c o r r e c t i o n was a l s o made f o r t h e d . e p a r t u r e of t h e e f f o c t i v c c e n t e r s of t h e t o t a l - p r e s s u r e t u b e s from t h e g e o m e t r i c c e n t e r s i n - t h e t r a n s v e r s e p r e s s u r e g r a d i e n t ( r e f e r e n c e 6 ) . The p r o - f i l e - d r a g c o e f f . i c i e n t s f o r t h e a i r f o i l w i t h r o u g h n e s s a t 0 . 1 5 ~ aad 0 . 3 0 ~ have n o t been c o r r e c t e d f o r t h e d i r o c t d r a g of t h c carbornndun s t r i p s t h a t w e ~ o u s e d t o psoduca and t o f i x t r a n s i t i o n ; t h i s c o r r e c t i o n i s s m a l l and unim- por tailt..
C r i t . i c a l speed.- ,The c r i t i c a l s p e e d i s de99ncd as t h a .speed a t which a break-down i n f l o w , c a u s e d by colil- p r e s s i b i l i t y o f f o c t s and Bnown as t h o c o m p r s s s i b i l i t y bur- b l e , o c c u r s . T h i s flow change i s u s u a l l y evsdenced by a r a p i d r i s e i n t h c d r a g c o e f f i c i e n t . I t h a s been p o i n t e d o u t i n s c f c r c n c o 7 t h a t , f o r p r a c t i c a l p u r p o s e s , t h o c r i t - i c a l s p e e d con be t a k e n as t h e v a l u e of t h e t r a n s l a t i o n a l s p e e d a t irhich t h e sum o f t h c t r s a s l n t i o n n l and t h e in- .
duccd velocities equa3.s t h e ' l o c a l speed of sound.
E x t r a p o l a t i o n of t h e c u r v e s g i v e n i n f i g u r e 3 show- i n g t h o v a r i a t i o n w i t h M of t h e maximum p r e s s u r e coof- f i c i e n t t o t h e c r i t i c n l p r o s s u r c c o c f f i c i c n t ( t h e p r o s s u r c c o c f f i c i c n t a t which t h e speod of sound i s l o c a l l y r e a c h e d ) i n d i c a t e s that t h c c r i t i c a l s p e e d of t h e T . A . C . A . 45-125 I*? b - * w w z i r f o i l i s h o u t 460 m i l c s p e r * hour n.f. 59' P.
( K c , = 0 . 6 1 ) .
Tho c r i t i c a l spcod o b t a i s o d by u s i n g A c l z c r e t t s t h o o r c t i c a . 1 v c r i n t i o n of t h c p r e s s u r e c o o f f i c i c i i t , ( r c f o r o n c o 4 ) , 1 -' So
s = 1 -
, i s a b o u t 7 p o r c c n t h i g h o r , Tho most
Jz2' tX ..-do 8 3 % ~ m:834
prob7.310 c n u s c of t h i s d i s c r e p a n c y i s t h c a s s u m p t i o n mzdc i n t h c d c v c l o p n o n t of t h o t h c o r g t h a t t h c i n d u c e d v c l o c i - t i c s a r c negligibly s m a l l , I t i s b c l i c v d d t h n t t h o c r i t i - c a l s i ~ c a d of t h e lT.A.C.8. 45-125 a i r f o i l czn b c i n c r c n s c d by s o m o d i f y i n g t h o d e s i g n t h a t t h o peak p r c s s u r c c o o f f i - c i c n t s on b o t h s u r f a c c s c y c roducad t o g i v e 3, f l a t - p e a k p r c s a u r c d i s t r i b u t i o n .
P r o s s a c d i s t r i b u t i o n , - Tho s h z p c s of t h o prcssu.re-
-
d i s t r i b u t i o n c u r v e s remained p r a c t i c a l l y t h o samc through- o u t t h c s p e e d r a n g e ( f i g . 2 ) . A s t h o speed was i n c r c a s c d , a 1 1 t h e p r c s s u r o c o e f f i ~ i o n t s a t p o i n t s a l o n d t h o t o p s of t h o c u r v e s incrc.-.sad a t n l n o s t t h c same r a t e cxcopt f o r spcccls cbovo 400 m i l o s p c r h o u r ( M = O i 5 3 ) , whore t h ~ i n & c r c c s c ?Ins g r s n t c r on t h o l o v ~ e r s u - r f n c e , ns i s i n d i c a t e d i n f i g u r o 3, Thc a d v o r s 2 p r o s s u r c gyc.dients over t k e r o a r 50 p e r o o n t of t h o a i r f o i l i n c r e a s e d trhon t h e specd was in- creD.sod b u t a p p a r e n t l y c3-used no s e p n r a t ion'. A t h i g h s p c o d s , soma u n r c p o r t o d p ' r e s s u r e - d i s t r i b u t i o n r a s u l t s , w i t h roughness a t , 0 . 1 5 ~ ' o n b o t h s u r f a c o s of t h e a i r f o i l , showed.
n l o s s i n l i f t t h n t w a s p r o b c b l y c a u s e d by s e p ? . r n t i o n ; no s u c h l o s s i n l i f t wc.s n o t c d w i t h roughnoss a t 0 , 3 0 c , D r z i ? . - Tho minimuz p r o f i l s - d r a g c o e f f i c i e n t of t h o smooth 3 . A . C . A . 45-125 n i r f o i l ; f o r z l i f t c o e f f i c i e n t of 0 . 1 , was 0.0058 n t n Royno1d.s Burnber of 4 , 5 0 0 , 0 0 0 ( f i g . 7 ) , o r nbout oac-half a s l a r g o a s t h o p r o f i l o - d r a g c o e f f i c i o n t of t h o Z.d.C,A. 0025 a i r f o i l ( r e f c r c n c s 5 ) . The v s l u o of vros Oi0068 ZO t h c l o v o s t Rcgnolds 3unbcr and i t r e - C d o mnincd Solow 0,0063 ~ v o l ? n t t h o h i g h e s t Roynolds ZTumbcr, which c o r r e s p o n d e d t o n s p e e d of 440 m i l o s p c r hour a t 5g0 F . , i n d i c a t i n g t h a t c o m p r o s s i b i l i f y a f f c c h s w a r e s m a l l .
Thcsc low d r n g v a l u c s a r c duo *bo extensive lnminnr f l o w s cxtoncliiig o v c r 40 p o r c c n t of t h o a i r f o i l up t o n Reynolds Numbor of a t l o a s t 7 , 0 0 0 , 0 0 0 ( f i g . 6 ) .
Thc p r o f l l c - d r a g c o s f f i c i c n t s of t h c z F r f o i l w i t h roughness a t 0 . 1 5 ~ 2nd 0 q 3 0 c w c r c , r c s p c c t i v c l g , 1 2 5 p c r - c e n t 2nd 7 5 ? c r c d n t l c 5 r g c r thnn t h e d r a g c o c f f i c i o n t s o f t h c smooth a i r f o i l f o r Ragnolds Humbcrs up t o 7,000,000.
Tho r z p i d i a c r c a s e i n d r n g f o r Roynolds 3umbors g r e n t o r t h a n 7,000,000 i s b e l i o v o d t o be,du.c t o tu.rbulent s e p a - r a t i o n n i d n o t t o c o m p r e s s i b i l i t y a f f e c t s . This b e l i e f i s s u b s t a n t i a t e d by t h o r e s u l t s of tho i ~ r e s s u r e - d i s t r i b u - t i o n inonsuremclits on. t h o n i r f o i l w i t h , xoughnoss ' a f 0.15c, a s 312s 9rov.iousBy .besen d i - s c u s s e d , and. @ % s o by t h e f a c t t h n k , t h o c r i f i c a l .speed was. noit; roachecl. . I t i s n o t known w h c t h e r tlxcrc v ~ o u l d have been s c p n r n t i o n i f t r a n s i t i o n hod o c c u r r e d a t t h e ssmc c h o r d p o s i t i o n Because of l a r g o s c a l o , r a t h e r t h a n .koughness. . . . a . , .
.. .
w i t h tho. t t n a s d t i o a - p o i n t l o -
The v c r i a t i o n of . bdo
c a t i o n w3.s n l m o s t . l i ~ c a r f o r Royaoldp l?u.mbcrs up t o 5 , 0 0 0 , 0 0 0 ( f i g , 81'; .The d r a g i n c r e a s e f o r a g i v e n movernont of t h o t r n n s i t i , ~ A ' ~ ~ ' i n t was a b o u t t h r e o Limes as l a r g e a s . t . .
t h o ikcrerzsb f o r the same movoment o f A ' t h o t ' r n n i i t i o n p o i n t on t h o 3,A.B.A.. 0022. a i r f o i l ( l r o f o r e n ~ e . - 8 ) . . p h i s d r a g i n -
g r v c s e . i s g - r e a t e r than can.-be .?ccountbb f g r bk i n c r a a s e d '
s k i n . f r i c t i o n a l o n o and i s p r o b a b l y cine mhinly t o p r e s s u r e . . . - dr6-i. I , A I . T ~ B p r s s s u r c - d i k t r i b u t i b n r b s u l t s i n d i c a t e t h n t t h o : c r i t i c ~ l s p e d . .of t h o 2 5 - p e r c c n t - t h i c k N . A , C . A . 45-125 . 1 - - n f r f b i ' l was n a o u t 460 m i l e s p e r liovr .at 590' 3 ' . f o r a l i f t ' 'coofYiciont of a p p r o x i m a t e l y 0.1. . The te,s.i; r e s u l t s i n d i - c a t e t h n t i t w i l l be p b s s i b l o f k r f h e r t o i n c r e a s e t h e c r i t - i c a l . spoed by s o p l o d i f y i n c t h e a i r f o i l . t h a t t h e peak grcs- . s u r e ' s ' w i l l ba re:'&uced t o a mo're uni'f.orm. p r c s s u r e d 2 s t r i b u - t i o n .
2 . The v a l u a of t h e p r ' o f i l o - d r a g c b e y f i c ' i e n t f o r t h o N . A . C . A , 45-125 a i r f o i l a t n Reynolds Wumber of 4,500,000 . .
w a s 0.0058, o r ab0u.t h a i k a s l a r g e c s th'e v a l u e f o r t h o ? J . A , ' c . ~ ~ . 0026 a i r f o i l .
. . . . .
3 . T - r a n s i t i o n d e t e r m i n a t i o n s i n d i c a t e d t h a t , f o r Reynolds Bumbers up t o 7 , 0 0 0 , 0 0 0 , l a m i n a s boundarp l a y e r s were m a i n t a i n e d o v e r approximnt e l g 40 p e r c e n t of t h e u p p e r and t h o l o w e r s u r f a c e s of t h e a i r f o i l .
Langley Memorial Aeronau+,icnl L a b o r a t o r y , B h t i o n a l Advisory Committee f o r A e r o n a u % i c s , Lnngley B i o l d , V n , , 1Tovcmber 3 , 1939.
n r > l u m a r s - d l d lacobs, Enstman I. : Mathods Employed in America f o m h *. Lhe Experimental Investigation of dcsodynamic Phenom- - cnn at Htlgh Speeds, Misc, Paper No. 42, B.A.C.A., 1936.
-.-,A !!!a!
2. Robinson, Russcll G . . : Spkrero Tests in the N.A.C.cl. 8- Foot High-speed Tunnel. Sour. Aero. Sci., vole 4, 5, March 1937, pp. 199-201.
he Cambridge U n i v e ~ s i ty iioronnutics Laboratory: The 1~5oasuFemont of Profile Drag by the Pitot-Trzversc Method, R , h M e go. 1688, British S.R.C., 1936.
. .
- . . . .
J.: 8bcr Luftltr&lfho boi sehr grosnen r • ~ ~ m ~ . . - ' .q .,.-: Geschwindigkciten insbesontiere 5ei ebonen SLrBmungcn.
.C - Physica Acta, vol. I, n o . 5, 1928, pp. = .
301-322 5. Jacobs, Bastman ?I,, 2nd dbbott, Ira H . : Airfoil Section Data Obtained in the N . A . C . A . ' ~ a r i a b l e - ~ e n s i t y Tun- nel as Affected by Support Interference and Other Corrections. T.R. Xo. 669, N.A.C.A., 1939.
6 Young, A. D o , and Mnas, 3. I?.$ The Behaviour of a Pitot Tubc in a Trnnsverse Total-Pressure Gradient. R.& M.
-'kl~o. 1770, British A . B . C . , 1957.
- # t r t m a S t & $ , John, Lindsey, %, F,, and Littall, Robert 3 . t The Oompressibility Burble and the Sffect of Com- pressibility on Pressures and Forces Acting on an Airfoil, T.R. No. 646, Nm~i.C.A,, 1938.
=3e?ker, John V. i Boundary-Layer Transit ion on t h e E.A.C.A. 0012 and 23012 Airfoils in tho 8aBoot High Speed Wind Tunnel, 3T.A.C . A . covfidontial report, TABLE I.- ORDINATES O F THE N . A . C . A . 45-125 AISFOIL [ S t a t i o n s a n d o r d i n s t e s g i v e n i n p e r c e n t chord] --...
- -- Lower surface Up;?cr surf z c e -- S t z t i o n O r d i n e t e S t a t i o n O r d i n a t e 0 0 0 0 1.132 3.448 1.368 -3.340 2.364 4.762 2.636 -4.576 4 . 8 5 1 6.528 5.149 -6.212 7.348 7 .,a251 7.652 -7.407 9.850 8.849 10.150 -8.333 14.862 10.327 15.138 -9.655 - .+r : 19.880 11.314 20.120 -10.518 ii ' 12.531 30.081 -11.559 , 29.919 59.960 12.906 40.040 -11.834 50.000 12.440 50.000 -11.336 60.033 10.760 53.957 -9.688 70.052 8 , 2 2 3 69.948 -7 - 2 5 1 80.053 5.165 7 9 . 9 7 90,052 2.076 89.968 -1.560
-;;."
9 5 , 0 1 5 .a19 94.985 100,000 0 100.000 -----
--. - --
- - 1i.E. raOius : 4.69 S l o p e of r a d i u s t h r o u g h end of chord: 1 / 2 0 F i g . 1 N.A.C.A.
a d) d).
a Fig. 2 M.A.C.A.
Figure 2.- Pressure distribution on the N.A.C.A. 45-125 airfo il.
c,, 0 . 1 .
N . A . C . A . .
A IT speed, m. p. h. (59 " F.)
Figure 3.- Effect of compressibility on the pressure coefficient.
C l , 0.1.
" A ?
a + q e " - 8 ~ 0 01 Fir4 0 1 - 4 8 gg g m o .
' & + 0 ,-I 5!+?
z ! d i .A
E ! : s
rl h * e s 3 g - 5," h m a
" 2
a d ' s P 0 .rl Pld 0
I. 2
d m " Ii 27 .-I ;f t!
Figure 6.- EXfecB of Reynolds Number on transition-point Transition -point /ocufion, z/c location. c2,O.l.
Figure 8 . - Variation of the section profiledrag coefficient with transition-point location, c2,o.l.
": 6 I+.
a , N.A.C.A. Fig. 7
Reynolds Number, R, mi//ions
Figure 7.- Section profile-drag coefficient of the N.A.C.A.
45-125 airfoil for various surface conditions.