Flight investigation at high speeds of flow conditions over an airplane wing as indicated by surface tufts

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Material Information

Title:
Flight investigation at high speeds of flow conditions over an airplane wing as indicated by surface tufts
Alternate Title:
NACA wartime reports
Physical Description:
6, 13 p. : ill. ; 28 cm.
Language:
English
Creator:
Wood, Clotaire
Zalovcik, John A
Langley Aeronautical Laboratory
United States -- National Advisory Committee for Aeronautics
Publisher:
Langley Memorial Aeronautical Laboratory
Place of Publication:
Langley Field, VA
Publication Date:

Subjects

Subjects / Keywords:
Bombers   ( lcsh )
Lift (Aerodynamics)   ( lcsh )
Genre:
federal government publication   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Summary: Flight tests were made at high speeds with a P-47D airplane to determine the flow characteristics, as indicated by wool tufts, on a section of the upper surface of the wing. The behavior of the tufts, which were distributed over a section of the wing from 39.5 to 52.5 percent semispan, was determined from motion pictures. The tests were made in straight flight and in turns under conditions in which airplane lift coefficients from 0.10 to 0.54 and airplane Mach numbers from 0.58 to 0.78 were obtained. The results of the tests indicated that the flow remained smooth over the test panel until the critical Mach number of the panel was exceeded by 0.08 at a lift coefficient of 0.10 and by 0.05 at a lift coefficient of 0.50. Beyond these Mach numbers, the tufts indicated unsteadiness of flow and, finally, local separation when the Mach number exceeded the critical value by 0.13 at a lift coefficient of 0.10 and by 0.10 at a lift coefficient of 0.50. The region of separated flow originated in the neighborhood of 30 percent chord at high lift coefficients and 45 percent chord at low lift coefficients. Separation appeared to extend over not more than 15 percent chord.
Statement of Responsibility:
Clotaire Wood and John A. Zalovcik.
General Note:
"Report no. L-91."
General Note:
"Originally issued June 1945 as Confidential Bulletin L5E22."
General Note:
"Report date June 1945."
General Note:
"NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were previously held under a security status but are now unclassified. Some of these reports were not technically edited. All have been reproduced without change in order to expedite general distribution."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 003613488
oclc - 71211444
sobekcm - AA00006281_00001
System ID:
AA00006281:00001

Full Text

[A*


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS





WARTIMlE RE PORT
ORIGINALLY ISSUED
June 1945 as
Confidential Bulletin L5E22

FLIGHT INVESTIGATION AT HIGH SPEEDS OF FLOW CONDITIONS
OVER AN AIRPLANE WING AS INDICATED BY SURFACE TUFTS
By Clotaire Wood and John A. Zalovcik

Langley Memorial Aeronautical Laboratory
Langley Field, Va.


WASHINGTON
NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of
advance research results to an authorized group requiring them for the war effort. They were pre-
viously held under a security status but are now unclassified. Some of these reports were not tech-
nically edited. All have been reproduced without change in order to expedite general distribution.


L 91


DOCUMENTS DEPARTMENT


Z CB No. LE2 :






































Digitized by the Internet Archive
in 2011 with funding from
University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation


http://www.archive.org/details/flightinvestig001ang





71/2 '*~


N ICA CR No. L5E22 CCNII DENT I L

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COI [c.E-TIAL z

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vi. A .I MrT'PLAJUE .F'r A3 I.EICATTD LY 3T [... A '"

3.. Cliteire? 1.'o d -rid Johr. A. Zal.'.vci





7lic'ht tests ,ecre r-s:'- at hi h s' >e- s jith a
P-47D ri'rpl,:'.e to det-i'rin? t'ie ,.-:' v :-aratcristics,
as indicated ty w. cl tufts, cn a rectior, o0 Lh.t up;-er
surface of the vwl.E. T-.e c-r.avic.r "- t.e .:.its, which
were distributed c1,er- a o or. f. t.:- vir. from ; .'
to 52.LH percent scmi.s'pan, i,:s deterr:,;i.- fr.m. i .:n
pictures. Th-e ezsts war'e .,'de in :traig-.t rli.fht ani
in turns un.er co-.,n it:oi s 'i ';hic:h Eir- i lPne 'ift co-'-
ficients fr.-m J.lu to .5 .arnd a.irpilane r'sl. r.luenb-rs
from 0.5.l to U.'_ .er3 c .btair.ed.

The resu:.lts f t-... t s3ts indicat-'.. tr`. t t flr.
remained smnothi over- ttie ts--.t panel ,.Hitil : ; c. it icalL
Mach nLum er cf the pan'.-. was ex-eedee.d : -.'.'. S t a
lift coefficitnt :f :3.1 an b- C.u5 at 1 i .it co-f fi-
le'nt ..f 0'.50. Pnrycr i the 3 n,, t rc n tuts
indicated .t!n teadlIne of 'lc.' e ind, finill:, lo,'al
se3 arat-crn 'rihen t:,e Wach niu:,.b: r xcee :ed t'.e critical1
v le by 0.1C at a lii t icse;' Tici:rnt c'f .10 .nn. o:. C .1
at a lilt c:effiF -int of 0.5'07. rF; :.e"Icn o-' se.t-rat 'd
flew originatE d In t. ;heir:e ir hborn od of 'C --rc.-.t chrd'
at Lith lift coefficients an;d .5 .,.rc'--t chor-6 at low
lift coo fi' 1c ir, ts Se srat 'olr a:,.,E.:ar-.-d to : c.Lend o'.ver
not rmor; t:;an 13 percent chjrd.





In the course of fll -t tests rsde tc d -tcrmin tihe
profile-drag chiard.teristics o.f th, vwin. cf a F-47D' air-
plane, a fecw \ocl tufts vwie fst'ieci to tt. wi.in c'urfaco
to permit visual obsc'rvctlon of t.'- oi .,cti n of ficw In
tne boundary iSvyer. Ti'vr behavLor- of t. tuf t;i at iig.h


C.'1 i.FIDELiTI AL








2 CON O'lirTIAL iTACA CB No. L5E22


speeds indicated disturbances in ube flow over the wing,
apparently associated with compressibility effects, and
suggested that tuft observations mrght provide interesting
information on flow o'-L-nc.i-n~l. at high speeds. A more
complete tuft installation was therefore made over a
section of the wing surface between 59.5 and 52.5 percent
semispan from the plane of symmetry. The tufts were photo-
graphed during flight at high speeds. The tests were
made in strai",.t flight and in turns under conditions in
which airplane lift coefficients from 0.10 to 0.54 and
airplane ach numbers from 0.58 to 0.78 were obtained.
The flow conditions indicated by the behavior of the
tufts are presented graphically herein for a few typical
flight conditions and are correlated with the flight
conditions.


APPARATUrS DT TESTS


Tufts were located on the upner surface of the
right wing of a P-47D airplane (fig. 1) at four nirmn-
wise stations: 39.5, 43.5, .8, and 52.5 percent semi-
span from the plane of symmetry (fie. 2). The tufts
consisted of strands of white wool yarn arrrj-i-?ed in
chordwise rows with each row attached to the surface
by a continuous strip of black "Scotch" cellulose tape.
Spanwise chalk lines were drawn on the surface of the
wing at intervals of 10 percent chord, and each line
was identified by a number beginning with 1 at the
l0-nercent-chord station and continuing thr'i.h 7 at
the 70-percent-chord station (fig. 3).

The wing of the P-.!7D airplane incorporates
--nublic S-3 airfoil sections, which have pressure
distributions similar to those of the NACA 250-series
sections. T'e aver:,.' chord of the test panel was
about q6 inches and the average thickness was about
12.6 percent chord.

The behavior of the tufts during the tests was
photograp!-. d with a 16-millineter motion-picture camera
operating at a seed of anproximately 32 fra-es per
second. M easurements of normal acceleration ind free-
stream i,,Bct pressure were recorded by means of
NACA recording instruments. The altitude of the tests,
indicated by an altimeter in the cockpit, was noted by
the pilot.
CO ITiD i' ['TAL








UAC LE. ilo. L3E22


T Th tests were ade in str-ai : !; fli-t and in turns
11- to L g) et ,i alti-tude of 2 ''C feet :.r. at
indicaced airspeed: fr:om 515 o 150 miles pnr h-cur.
The irnli' ne ..nch r..bvrs r'I. i from .1 to ''.73, -nd
the ir :-.ne lift cce ff.;le it :i.. : ed fro 03.10U to ') 4-.


FP??7S~iT'* j~ T iCT t" .7*JTJ'3
Fr TS---n T".c --," --. of. t`3


A.n enl.. r *ne cf ie r:'.. f t .l-.e *lot i -ni c 'i re
fil-1 t k'..en : n .-'i!t s s' or.Ti s fi ure The
q'I':-.Jlit t 7 1- r-o o r._r s .'is, : n -'-l t1 -Co roo to
cer' r -s ti .rnfatt '?" ren :' ci i 3 n in fi r-
ures 5 to C, '- re e, .-et1 s b..e c -.n '..e ori -nal.1
rnhlto ra has :ie us3cd to i 'lust.ia' t, .or u few t'.-ical
fl ;... t cor -.t 'ons, e flr.w c,:_: c ors ir.:I' c ted b;, t-he
tu"ts. T-.e flcw o": t i tLons ior P .ii cus rC. r.: 1 -t
coefficiEnts at conrtas.t rinlr.3 cih n'-..bers of .J.t
and 0.71 are cIw.c w n f .I:r-ea c n. C, ir s t. ve 1r; the
flow conk'. t in.is Ir '.:r : o.s .,ir"-l.ne I.. n't. t rs .t
constant i: iI r.e '' ft c' cffic._e:-- cf 0.I. and i .;, are
shown in .''i7 .ues 7 :d 6, rs-,nectilvel 3na3:;i:ch is t he
i !..'1 o te "' .,-ere cov'.'cd orl" cl.e fo 'v. ri 7'-. t
3 nrerca:.t c'ord, te flow cot-'iti.: s 1c'.'nstre. of
this r ; or. :ar' not ;:no';n.

'rn? fiow cndt n'-a .'5. -te: t : t at
various 11 t cc fi c -.ntso a-id ach :orb are s-' -iar zed
in _Lir' .ie '. Th' intern:-etat-on of ti'.r- r-t\"..rc.r of tV-c
tufts is as follo.;s: Tu -ts li.,'n train t. ac: and
moticnle *s iniicate o,,, th f'lo-, tdU'ts cc;:cill: t'n..
latera.ll ..ndi carte ru-. t .C'r fl: tn_ tufts "'fiorning"
arou-rji le surely .o 1"inr. CurvYd on the .surface in tcate
flow seo:aato-r. (C,,-oa"e i? f is. 4 fn ci (d).)

The cr.i. t 'c:* ". h n---:r cr of -:'.n- sect tions
at 25 and 65 .-r-crcent semr' 3ran and t.-e L.-ach n-i-iber at
wh.c!- shock .as first Sv'cient _n ::e vwal:e at u7 rpern ent
se-niscan w.ere? Cet.r 'ed I'rOm tYe 'cults (uin-r'.lished)
of eottier tE sts of the P-liPr rp;.K1l n-i2 are corrsred
in i'.cure 10 -rit t1- ;"3c'' n'i.'rbers -t wi-'ct flov dis-
turbance and fl"ow seSarat'on w -re first ".rdic:tted in
the present tests. ('C'in- statiocns In i;s. 13 rnd 11
are desimr.ated 2y/b, ..'.here y 13 *-.-e .. .str 'e C. the
wirn station t'rr-m the rlne of 3,-yn-etry and D is the
win- span.) The deter.rcinA.tio. 0of ..;h critical Mach


0tnu 'TrT,;-ilm TT r,


C .. ;l"I D .I T I.AL








CO],'iT. :I.TI AL


NACA CB No. L522


numbers involved extrapolation, by the von Ka'rma'n method,
of oressure-distribution data obtained at i.ach numbers
0.02 to 0.06 less than the critical value. T:.- airplane
lift coefficients were correspondingly modified _y, means
of the Pranatl-Glauert relation. Th'u pressure-
distribution measurements were obtained with static-
pressure tubes and therefore, according to the results
of reference 1, the critical "'.Tuh numbers ;.'; be as
much as 0.01 higher than would have been obtained
from pressure measurements with flush orifices. The
critical Mach number at 46 percent semispan, which is
the center line of the test panel, was obtained by
linear interpolation between the critical I>ch numbers
at 25 and 65 percent semispan.

A comparison is r-ade in figure 11 of the flow
behavior and the critical Iiach number obtained in
fli'.t and in the Ames 16-foot hi..h-speed tunnel on a
0.5-scale model of the P--47D airplane (reference 2).
The comparison of flow characteristics is made on the
asi"r.iption that tuft behavior is interprett'- in the same
way in the wind tunnel and in flight. The critical Mach
number shown for the wind-tunnel tests was determined
from pressure-distribution measurements made with flush
orifices at 41 percent sermispan.


DISCUSSION OF ..SULTS


The sketches of figures 5 to 8 show that, as Mach
number or lift coefficient increased, the flow first
became unsteady over a s.ii;.l chor"'ise rel:"-n; this
re -Lon then became more extensive, and finally local
separation occurrc-.. The re;'Lon of separated flow
originated in the nel:.borhood of 30 percent chr-.:-d at
1.1-, lift coefficients and .5 *-rcent chord at low lift
ccefficients. TP.e re ion of separation appeared to
extend over not cmre than 15 percent chord and .,3
followed by a region of unsteady flow beyond which the
flow again was steady.

T!-ree distinct re !.-.s of flow are evident in
figure 9. At a lift coefficient of 0.10, -,: flow
remained smooth up to a ..iach number of 0.75; to-'end
this li'ch number, the flow was unsteady and local flow
separation occurred at a .T.vh number of 0.'.. At. a


NFPIL'- '' ,AT








,ACA CO Ir. LSE22


lift cce.f .cient of' 0.5,0, ths low remaiind soth u
to n.aci! nu:nlDcr of U .2 and local! .ow separation
occurred s.t a s.ach nunitir cf '.6 '7 C omra: riso n of th,- e
res i.t3 il-h tj Ie tical I.ach i nru.,b r in fitu.re 1.'
1i c.-. c tes ths t the fl ow re r e '. sm.' ith n. til the
crit c:al i' ach n'iumb:r was evxccte --'. -" to '.',
Jeon:r- in.q on i-'-t c oeffi c ient. Lob dl se r ,rat.Lon r.f
flow occ'.- red. "-T.en the -critical i'.ac num-ne w-as e :eeded
by 0.10 to 0.13. T'e .'sc, n ;i!.l r. at which c.morres :itility
shock :wa's .irs evil.J nt in the v1.a':6e ;.t 6.3 percent -emi-
span was ar.parentl'r Excleeed 0--...-5 to 0.)3 ~ fore
local flo- seo:-rsatior cc'.urre].

The cor.3:-ison n figure 11. o' lijht a.n wini-
tun-nel results in. t.s l:-'-at -he .-:...eti c.l .ch nur.ier
was 30.0) co 0.31 ht'ber, e p? din o! 1ift coef ficie t,
in the flight test ta-n in the tlsts of cl-e 0.5-s ale
rmoi.1 o. the P-L7D .lrrpl.: lne in r t, 3s li-foot hi.h-
spaed9 tunnel 'el-e c ch num.b ,r jt iich local separation n
occurred L,.as 0.02 n.T .r 'ir flight chain n the tunnel.
The fli.hi a,-' tunnel re.2lts .qre t:,_.retfore in .-ood-
agreer n' t.





:li.;ht tests maie at li5h se.is vth a P-. 'D i r-
clane to 'e.te rine the flo'A charac terist ., is in..cated
by ,Vrnol cuts attachc.-d to a se action of :-e ,-'-er uLrf2':ce
of the wvin s ho..wd tkat the flo I, i~nine: ooLh until
the cri t:ical "ich n'Liter of t-e vwin-- section w:is xc.eeaed
b, 0.03 a a 1 ;'t coer-fi.cent of .10O anC b--y 0.u ac a
lif t cce "'I.ci nt cf 0.50. Fe ro:,d L't"-ioes. h n ,mbers,
+the tufts -nr,-1icated '.mutead inss of flow and, finall:,r,
local s. i.ar t.'t on vhen Lthe ch nuj,:b.,w ex ci e ;,ed thc cr-itical
value : b, ).15 at a 'i't cocffic i-nt c.' 0.1J and b-. 0.10
at a 1: t 'oef iccient of 0 0. The -:ejion cf 3eparatod
flow o iginatec in t'-e neii:hbori(ood of O -, crc.:-nt chord
at h ih 1. 't coe,:fic nts arnd '.5 percent chord at low
lift coefficients. The IreC-ion of seonration anneire.r
to e.tLend over not .:,ore t.,arn 15 ,.erc.nt ch-ord. Ccom-
parison of these results with' results obt_-ined in ths
Amires 16-foot high-sped tuni'el on a 0.-,-scale .oel of


CON? -IET. TIT L


CO'",) -7ID .-T T-IAL








NACA CB '-.. L5E22


the P-47D airplane indicated ,ood agreement between the
flit.t and tunnel results.


L-.:i;ley Memorial Aeronautical Laboratory
National Advisory Cormmittee for Aeronautics
Langley Field, Va.








1. Zalovcik, John A., and Daumn, Fr': L.: Flight
Investigation at High ::ach Numbers of Several
j.ethods of T.Ijasuring Static Pressure on an Air-
plane "Ti!.. NACA RB L'4. L10Ha, 1944.

2. Hamilton, William T., and -rd-y', Lee E.: High--peed
;1:-.-Tunnel Tests of a 0.5-Scsle ..odel of the
P-47D airplane. NACA A:', No. 5D20, 1945.


CO; 'IDE LTIAL


CC --IE -.i.IAL









NACA CB No. L5E22 Fig. 1









































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NACA CB No. L5E22


489.3


Span wie
location of tufts


NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS
CONFIDENTIAL




Figure 2. Plan view of Republic P-47D airplane showing
spanwise location of tufts.


CONFIDENTIAL


Fig. 2

















































I










II







NACA CB No. L5E22


Figure 3.- Test panel on right wing of Republic P-47D
airplane, showing rows of tufts at 39.5, 43.5, 48,
and 52.5 percent semispan. Numbers identify span-
wise lines at intervals of 10 percent chord.


CONFIDENTIAL


CONFIDENTIAL


Fig. 3



































yr


































































I4







NACA CB No. L5E22


Figure 4.- Photograph showing tuft behavior at
an airplane lift coefficient of 0.49 and at
an airplane Mach number of 0.71.


CONFIDENTIAL


Fig. 4


CONFIDENTIAL








NACA CB No. L5E22


CONFIDENTIAL


Steady flow
Undeady flow
Separated flow


NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


Figure 5- Flow conditions oit e t section
for an airplane Mach number of 0.69.


Fig. 5a-c





NACA CB No. L5E22


Steady flow
Unsteady flow
Separated flow


Figure 5-


NATIONAL ADVISORY
(f) COMMITTEE FOR AERONAUTICS
CONFIDENTIAL
Concluded.


Fig. 5d- f






NACA CB No. L5E22


Steady flow
Unsteady flow
separated flow


SI ELL-----^ NATIONAL ADVISORY
(C I) COMMITTEE FOR AERONAUTICS
CONFIDENTIAL
Figure 6.- Flow conditions oft test section
for an airp/ane Mach number of 0.7/.


Fig. 6a-c






NACA CB No. L5E22


CONFIDENTIAL


C (FL)
CONFIDENTIAL


/ NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS
Steady flow
Unsteady f/ow
Separated flow


Figure 6.-


Concluded.


Fig. 6d




NACA CB No. L5E22


K


Steady flow
Unsteady flow
separated flow


!-N- I NATIONAL ADVISORY
(C) C DE COMMITTEE FOR AERONAUTICS
CONFIDENTIAL
Figure 7- Flow conditions at test section for On
airp/one iff coefficient of 0.13.


Fig. 7a-c





NACA CB No. L5E22


H steady flow
/Untieady flow
Separated flow


S^ NATIONAL ADVISORY
YE _s COMMITTEE FOR AERONAUTICS
() CONFIDENTIAL
Figure 8.- ~F/ow conditions ai fe3t section for
an airp~lne /ift coefficiend of 0.43.


Fig. 8a-c






NACA CB No. L5E22


o Smooth //ow
+ Unsteady f/ow
CON-IDE IAL x eparated/flow
. +I.


+
1..* +4


Beginning of
unsr c+ floHw/ /'IrU


Beginning of separa ton


CONF DEN AL


.2 .4
Lift coefficient,


-Separated flow


-Unsteady flow


-Smooth flow/

NATIONAL AD)VISRY
COMMITTEE FOR AERONAUTICS


9. Flow conditions indicated by tuft behavior.


.7



.6


.51
OC


Fig. 9


(


Figure


x x
x






NACA CB No. L5E22


.8


.6
-.7


r 5
c *


NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS
RFIDENTIAL
eg inning o fsepara tion ,QJ95<
S'Beginning of unsteady f/ow,
SF 0.395<
First indication of shock
in wake at = 063


at = 063
interpolated, = 0.46
f% nb


cr at =025


0 .2 .4 .6
L/ift coeff/'cient, C1


Figure /0.-


Comparison of f/ow conditionsindicated by tuft
behavior with critical Mach number and with
Mach number at wh/ih compressibility shock
was first evident in wake. P-47D airplane.


Fig. 10





NACA CB No. L5E22


.6


0
.J



Figure //.-


CONFIDENTIAL
----Figh
Ames /6-ft high-speed funnel


7 Flow separation

Beginning of
unsteady flow

Mcr at =0.46


C NFIE ENTI L 0Mcr = a4/
.2 .4 .6
Lift coefficient, CL NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS
Comparison of resu//~ obtained
in flight on P-479 airplane and in
Arnes /6-foot hgh-speed' tunne/ on
3J- eca/e model of P-47D airplane.


Fig. 11








































































































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UNIVERSITY OF FLORIDA

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