ACR No. L^08 1 NATIONAL ADVISORy COMMITTEE FOR AERONAUTICS WARTIME REPORT ORIGINALLY ISSUED April 191^5 as Advance Confidential Beport L5CO8 WIND-TUHHEL ISVESTIGATION OF EFFECTS OF A PDSHEB PROPELLEK ON LIFT, PROFIU; DRAG, FBESSDRE DISTRIBUTION, AND BOUNDARY-LA"XER TRANSITION OF A FLAPPED WING By Carl A. Sandahl Langley Memorial Aeronautical laboratory Langley Field, Va. NACA WASHINGTON NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of ^ f^^ 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 - 1J*8 DOCUMENTS DEPARTMENTJ 7^^ DiOHH • I FACA ACR Mo. L^COS i NAITONAL ADVISORY GOmiTTES FOR AERONAUTICS I ADVANCE CONFIDENTIAL REPORT V.T]\!D- TUNNEL IN^/EETir-ATION OF EF::^CTS OF A PUSHER PROPELIER ON LIFT, PROFILE DRAG, PFiESSUIffi D^ 3TRI 3UTI ON , AND BOUNDARY- LAYER TRANSITION OF A FLAPPED ?TNG By Cai->1 A. Sendahl SUH^^ARY Sozne of th-e sffects of pusher-ppopell-sr operation on the aerodynamic characteristics of a flapped wing were measured in the Langley propeller-research tunnel. The effects of propeller operctlon on the lift and profile drag of the wing, on pxessixre distribution, and on the position of bovindary- layer transition vjere obtained. The results indicated that, at fixed angles of attack and with flaps deflected, the wing lift increased appreciably with increasing thrust coefficient. V'lth flaps retracted, no appreciable increase in lift with increases in thrust coef- ficient 7/as measured. Chordwise pressure distributions at several spanwise stations indicated that the effect of propeller operation was greatest in the region immediately aheadi of the propellei' and that the effect extended out- board from the propeller axis for about 2.5 propeller radii. Measurements of boundary-layer velocity on the forv/ard part of the upper surface of the \N\xig, showed no appreciable shift of transition in the range of thrust coefficients Investigated. :ntroduction As part of a study of the eff ' -iiency of a piAsher propeller behind a low-drag wing, some m.easurements relating to the effects of the proc 3ller inflow on the aerodynamic characteristics of the wing were made in the Langley propeller-research tunnel. The data, \vhich are presented herein, show the effects of propeller operation COIIFIDSNTIAL HAG A ACR No. L5C03 c:i the lift dT the v/jng v/j th flaps retracted ai'id deflected, on the oressure distribution, en the section orrfile drag, and on the oositlon of ooundsry-layer trsorisition on the uooer surffce. APPARATUS AT'D T3^TS The cenerr.l arrangement of the ii-.odel used in the present investipietion is shown in fif^ure 1 end the r.:odel configurations, in figure 2. The ^eoir^etric character- istics cf the model sre a." follows: Wing area vvith flao retracted, square feet .... 77-27 Wing scan, feet lo.Oo Wine; chord with flap retracted, feet i;.952 Aspect ratio i' T ' * ' 5'34- Airfoll iiectloii r- ac.^ 6 J ,U-U20 ( aporoz. ) Flap chord, feet "'"T ^'^ Propeller diarieter, faet '-i-'O The wing v;a£ coriStructed of wood covered v.'ith fiber- board. For the tests to determine boundary-layer transi- tion, the v/ing was carefally srnded and waxed; h-wever, for the other'tests, including the measurements of orofile drag, the wing v/ss considerably less smooth, partlculiLrly at the leaaine: edge.. Pull-soaii landing flaos of single- slotted, doubie-slotted, and sT:>lit tyoes were used with the wing. The nacelle was fair-.d into the wing and no rrovisicn v-as msde for air flov/ through the nacelle. The three-blade oroooller with a i|-foot diameter was a Hamilton-Standard blOl design of modified Twitch distribution and right-hand rotation. (See fig. ;.) Ihe rrooeller was driven by a variable-speed variable-f renuency induction m.otor rated at 70 horsepower at JCOO rom. The orooeller blades were set at 22.5° at the 0.75-rr.diu3 station. The maximuin 'orooeller rotational soeed^was 3000 romi, and the maximum, wind-tunnel speed was dO mAles per hour. Tunnel speeds lov/er than the m^axim.um were necessary in developing the higher values of thrust coefficient of these tests. The range of thrust coefficients used was extended to values considerably higP.er than tnose of normal flight in order to accentuate the effects of oropeller operation on the aerodynam.ic characteristics of the wing. CONFIDENTIAL NACA ACR No. L5C08 COKPIDEriTAL 5 Lj fts v.'ere measar'ed over a range of tiirust loadings at flap deflections oT 0", 20'"', and ii-O'-^ and at geometric angles of at"i:ac''<: cf 0'^, ^' , i^ , and 9'^« Pressure distri- bution, profile drag, and ocundary- layer transition were iTieasured only with the flap retracted. The section profile-drag; coefficient v/as ineasured at three spanwise stations in the vicinity of the propeller. (Lee fig. i.) The limited space between the v/ing and the propeller necessitated mounting the rake immediately behind the trailing ed,'.",e as shown in figure U-. Both static and total pressure ■'"ere measured. The pressure distribution over the wing v;a3 measured v'ith a pressure belt constructed of O.OL'-O-inch copper tubes soldered together as sho^n j.n figure ^. The excess solder was scraped frorr, the surface of the belt, and an orifice with a diarreter of 0.020 inch was drilled into the vvall of each tube at the desired chordwise locations. The belt was then formed to the wing section and mounted on the surface. Boundary -layer transition was determined from miaasure- ments In the boundary Ipyer over the forward 60 percent of the upper surface ol' the wing at seven spanwise sta- tions. (See fig. 1.) The total pressure in the boundary layer v^as m.eesured with O.0i;.0-inch stainless steel tubes flattened to an inside height of O.OOo inch. (See fig. 6.) The geom.etric centers of the tubes were set 0.011 inch above the wing surface. The velocity in the boundary layer v/as calculated by using the total pressure in the boundary layer and the local static pressure previously measured with the presrure belt. SYMBOLS Cr total lift coefficient of wing with propeller .rp , , /■Resultant vertical forceN operating i 1 V 0'-' ACt increment of lift coefficient due to propeller P thrust inclination / \^e rtlcal comp one nt of p ropelle r a:xia l for e e _ Tq sin a \ CCNFIDEFTTAL CONFIDENTIAL NACA ACR No. L5CO0 Ct r.et lift coefficient of wing /'Cj - LCj \ Cj cecticn profile-crag ccefficient ( fjG ction p roll 1 e drsg\ 0_G y Tp effective thrust dis'c-loading coefficrent based on propeller dis'^ si'ea I \ O / T„ effective thrust, pounds D propeller diameter, feet V_ free-rtrean velocity, feet oer second u velocity in surface direction inside boiuidary layer, feet per second S win 2 area, square feet c v;ing chord, feet p mass density of sir, slugs per cubic foot a angle of attack, degrees; r.^easured betv/een thrust line (coincident v;ith chord line) and relative wind; corrected for jet boundary 5..-, flap deflection, degrees X distance from leading edge of wing parallel to choi'd line y lateral distaace from plane of s;;,Tnrretry q^ free-stream dynamic pressure (~-r'^o ) p local static pressure on v.lng Pq f ree-st reaw static pressure CONFIDENTIAL MCA ACR No. L5G08 CONFIDEFTIAL 5 J , , . . . , -^ "-"Po ^ P averac<;e chcrav.'ise pre3sure rf.'cio ; RESULTS Ai^D DISCUSSION The rerults of thi ? investigation £>re nressnted in four sections siaovan;? the effects of propeller operation on (1) lift, (2) chordv.lse and spsnv/ise pressure distri- bution, (5) boundary-le^er transT ti on, and (k) profile drag. The d&ta are expressed in nondimensional coeffi- cients and have been corrected for jet-boundary effects. In a preliminary comparison, it was found that lift with oropeller operating at T^ =, would agree with lift for the propeller reinoved within erperinental accu- racy. The lift coefficients at T^ = in this report may therefore be considered cs propellei'-reir.oved vslues. Effect of nropel ler operatio n o n lift.- Lift with power on is considered to nave fo'ur components: ''1) the lift of the wing at T^ - 0, (2) the increment of lift of the wiiig caused by operation of the propeller, ( ^ ) the vertical component of propeller axial force, and (a.) the propeller normal force. The maxim.um propeller normal force developed in these tests 1? est^'mated to be within the scatter of experimental points, Com.ponent iZ), the increment of lift, is then obtained by deducting com.- ponents (1) and (5) from the mjeasured resultant vertical force. In evaluating component fj), the propeller axial force vifas assumed to be equal to the effective thrust and independent of sngle of attack at a given value of advance-diameter ratio. The variation of total lift coefficient Or with ^T thrust disk- loading coefficient T^, is given in figure 7 for several angles of attack and several flap deflections. In correcting the angles of attack for jet-boundary effects, the 'total lift coefficient Ct at T.^ = 1.0 Jrp was used. This simplification introduced Inaccuracies in angle of attac- of the order of tO.J'-' and corresponding changes in total lift coefficient of ±0.012, which is within the scatter of the experimental points. The vertical com.ponent of propeller axial force has been COLTIDSLTIAL COliFTDEFTIAL NACA ACR No. L5CO8 deduotec" from ths f si Ted curves of fi,q;ure 7j ^^nd the I'esultixig net lift coefficient i3 cross -plotted against tnele of attsck at three values of T- in figure 8. In this figure, the angle of attack has been ooi-rected ty ucing tbe totel lift coefficient at each value of T^ . The curves of figure 8 indicate thst the slope of the lift curve is approximately independent of T^ . With flaps retracted, propeller operatior. - even at high thrust coefficients - did not aoprecirbly affect the v.'ing lift (fig. 8fa)). Y'ith flrps deflected, however, the lift Increased v.lth Increasing Tp . The increment of vlng lift resulting from propeller operation is the difference in lift between the curves for Tq = and curves for the propeller operating in figure 8 and is attributed to only the prooeller inflov. It is noted that a British investigation (reference 1) shows larger increases in lift due to propeller operation th?n were ■measured in the present investigation. Less lift v.as obtained -at T^ = with ■t"he double than ■'"dth the single slotted I'lao. The difference may have been caused by incorrect design of the double slotted flap. Effect of oro-'eller cr^eration on TDressure distil- b uti oh. - The chordv/ise pressure distribution at several spanwise stations and several values of T-, is p'iven in figure 9' The maxiTrum observed decrease in local pres- sure associated with oropeller ooeratlon occuiTed near 1 'v ' ' I the trailing edge at '^ = O.c^O, the point of measure- ment nearest the thrust center line. The pressure decrease ' at 6^ = 0'^ was approximate I7Y' the same over the upper j and lower surfaces, an indication that there was no , aopreci '-ible change in Hft. This result is in agreement with the results of vhe force tests given in figure &(a), From figure 10, in v.'hich the average chordwlse pres- sure ratio is plotted against spanwise station, it may i be noted that the propeller effect extended outboard to j '— -1,3, or about 2.^ propeller rcidii from the propeller i I axi s . I coijpide:*tial NACA ACR No. L5C08 COKPIDEFTIAL 7 Effect of pro pelle r operation on bounde.i'y- lajrer trsnsition.- The ratio of the velocity st a constant height TO'.Oll in. ) in the boundary layer to free-strean velocity u./Vq is plotted as a function of the distance from the leading edge y./c an figure 11 for several thrust coefficients a^id test velocities. Wo appreciable shift in transition associated with propeller operation or with Feynolds n-urr'ber v-as ireasured. This result is in agreeiTient vath reference 2. Effe ct of pr opell er op era ti on o n s ec tion p rof il e d rag . - The section profile-di'ag coefficient was measured at three spanv/ise stations in the vicinity of the p*ro- peller. (Sec fig. 1.) The variation of section profile- drag coefficient with thrust disk-losding coefficient is given in figure 12 for three test velocities. The rather high orofile-drag coefficients measured at 7^=0 are attributed to surface roughness near the leading edge, which presurrcbly caused transition to occur much farther forward than with the highly polis}:ed surface en which the transition measurements of figure 11 were obtained. Larger increases of section profile-drag coefficient with increasing thiust coefficient occurred than c^n be accounted for as increased skin friction due to the increased velocity in the propeller inflow. These Increases in drag coefficient are probably due to the action of the low-pressure region in front of the pro- peller in drawing low-energy boundary-layer air froui other sections of the wing tov/ard the sections ahead of the survey rake . COFCLTJSIONS The foregoing analysis of measurements m.ade to determine the effects of pusher-propeller operation on som.e of the aerodynamic characteristics of a low-drag wing rndth flaps indicated that; 1. At fixed angles of attack snd with flaps deflected, the lift of the wing increased appreciably v.;ith increasing thrust coefficient. Z. Changes in pressure distribution over the wing caused by propeller operation v;ere largest imir:ediately ahead of the propeller and extended outboard to approxi- m.ately 2.5 prone Her radii fromi the propeller axis. COIvFlDENTIAL 8 CONFIDEFTIAL NACA ACR Nd. L^COS With flaps retracted, no appreciable change In vi.ng lift or span load distribution -.vas measured. 5. No appreciable shift of transition vd th vai-ia- tion of thrvist coefficient v;se measured. Langley T,"e^"norial Aeronautical Laboratory National Advisory Cormnittee for Aeronautics Langley Pi eld, Va. REFERENCES 1. Smelt, P., end Smith, F. : Tiote on Lift Change Due to an Airscrew !:ountcd behind a ?lng. Rep. No. 3. A. ISlk, British F.A.E., Dec. 19^8, and Addendur^, Rep. No. B.A. I51I+C, April 1959. 2. Hood, Manley J., e.nd Caydos, ^': . Ed'.vard: Effects of Propellers and of Vibration on the Extent of Laminar Flow on the N.A.C-A. 27-212 Airfoil. MACA ACR, Oct. 1939. GOIIFTDENTIAL NACA ACR No. L5C08 Fig. 1 •o o E o ■p C o B o> bO C CD ^ CO CD C <1> C5 0) NACA ACR No. L5C08 Fig. 2a < O 1 u 5 Q QJ t— I M fe. bo Z C o +J CO' u 3 bo •H NACA ACR NO. L5C08 Fig. 2b < I — I E-c Z Ed Q O < >— I Eh 2 . Q 1—1 Eb O o o- . 1X3 X3 .— 1 (D <^-i D C t:) •H 0) -fJ jj c iJ o o u ^ m 1 0) w • — 1
  • O U c o t3 ■-t U +J fc o o D. C 0) m x: «d &H S • 03 t^-l p. 03 NACA ACR No. L5C08 Fig. 3 CONFIDENTIAL B/ae/e p/ort form (deve/opecf) Spinner outli'nz D b AJO--*" .cff.ze \ ^ /o h/b^ \ / ^ ^ .ObM \ / X \, \ f V \ JOS.ZDSO / 1 \ .A / \ \ jOi.lk 40 / \ s*^ S \, \ V ^ \ .03.IZ30 \ ^ NATIONAL ADVIS (jQHiumrr ehd aed ORY JNAUTICS \ ^ 02. M 20 ^ "^ -^ CON FIDE^ TIAL ^^ ■— - -^ ni nd /r, .Xr .3 .5 .e r/R .6 AO Figure 5.- Plan-form and blade-form curves for the modified Hamilton Standard 6101 propeller. R, radlua to tip; D, diameter; b, section chord; h, section thickness; r, station radius; p, section blade angle. NACA ACR NO. L5C08 Fig. 4 CONFIDENTIAL Figure 4.- Wake-survey rake installed between wini trailing edge and propeller. CONFIDENTIAL NACA ACR NO. L5C08 Fig. CONFIDENTIAL Figure 5.- Pressure belt Installed on wing. CONFIDENTIAL NACA ACR No. L5C08 Fig. 6 ►J < I— I E-i •z, Q l-H Z O o bo C C O t3 CO 3 3 CO CO ^ y ^ ' .-;>. ^ ' ^ i> Split floD 1.0 2.0 / y' / 1.0 /' ^- ^ -^ y ^^'^ r-^ ;^ 5p/it f/oD — — 12 ^ ^ ^ /.^ ^ *^ r^ »^ A ^ ^ ^ Double jslolted floo \ 1.0 ^ -<5= B^ rt* ^ ■O' Sina/P' ^/oftpd flan 1 1.0 2.0- 1.0 — ^ ^ 8 ^^ ^'y- .^ .-' > ^ ^ j6 ^^ ^ ^ ^ ^ .4 .2 Double slnlled flan \ /^ 2,0 — ■^.' '^ y^ .^. >- — -< /> "^f- y. ^ ^ — CO ^FID ;Nri IL Sinole slotted floD \ 1 (a) cTf, 0° Angle of oltackj oc^ deg (b) d'f, SO' l.i 1.0 A'Z 1 ^ '" 0— ^ ^^ --^. ^ ^"^ ^ ^ ' -^ \ "-a z .4 6 ¥ ij ) i^ ^ \ ^ ' ^ \ ^ =^< J f jf If w_ f t f ( f % \ B^ "1 "vj O+x .^ ^^ O^l 1 P M > \ \ =-< r f ^ 1 ^ 1 ^ if is s 1 SI 1 \ *^ 5^ -c ^ o + 1 K^O§ 1 >; P ? , ) i ^ I z I a I s . f s 1 i N ^ I I I OO ^1 f I t I 55 I -I <3 1^ W> ■«< ?l -Sk l> NACA ACR No. L5C08 Fig. 9b -$ o + x 5j Q H w- Q V . . ^ ff 7 n ? f 5' ^5 \ \ N ~$ .?! Q '^^ 1 ^ ? m I M M !/*• j ) ) ) 1 ! V =_ -(^ f J f ¥ r r 1 \ \ ] N + ^ u" C.S ^ 1 ? I , j 1 1 I f 1 1 i 1 ; ■P \ ^ —if o f E i f si 1 - ^ r 1 1 f * > i \ *=" y "1 + > "> k" C^^ ■^ n; p i < i 8 j J 1 f /r fef j ! i I 1 1 ' } ? V _ fP— I «i I I I .1 ■(S ts tf- ■QN NACA ACR No. L5C08 Fig. 10 P-Po -/ o -/ ( ;ONFlpENTI \L (ypper ^Si^rfprce ■ — =. =^= -— ===» Tc r Prope//er tip radius 5^ /,// Lo\A/,^r surface 1 --^ :^^, - __^ o .2 .4 .6 .8 1.0 I.Z Spaniuise sfafion y/c (a J oc.^ e.o°. 1.4 P-Po P-Po -/ (Jpcer .jurface --- —■ , .__ a— o ' - ( \m\ )ENTI \L Tc / — Loiv'er surfaice .53- 1 1 1 I'll 1 -—— __ ■ — ■-- COM Ml TIONAL TEE fOI ADVISORl AERONA JTICS n o .z f4- .6 ,8 /-o /^ 1.4- Fiqure /o.- Variafion of average pressure over upper and /ou/er surfaces u/if/i thrust coefficient. Single slotted flap] p-f,^. NACA ACR No. L5C08 Fig. 11a u/K o 4 cor FIDE jri* y/c, ai 5/ // \ \ ^ \ 1 ■^si. ^>s / 1 s / \ J y/c ,0.71 I&' 1^ :^^ ■- — ■ . r "^ ~^ =§ 5^^. I ^N r \ } ■^ / .. O .1 .2 .3 .4 .J- -6 (VVo ^ y/<:, .t V A ^_ / ■ --> V, ~^^ ^^ ,^ / '1 ** \, // ' <^ ^ > '/ 1 y/^ -- V^ / ^ -^ en MMin ONU ADVIS Et FO 1 AER inv NAUT CS O ./ .^ .J /f' .-T .6 Disfame from leaa/ing edge , '^^c _ y/c z o / — Ji t> i \ C — , ^ u/K A ^ ^ i>. I ^ --^ / ,z co^ not ITIAl O ./ .2 ,3 ef -S .6 D/ifanne from /eadrng ec/grSj Vc re o w ('j) Vo , 33 mi/es per hour (approx.). Fiocire //.- Variation of bo(jnc/ciry-/Mer ire/ocif'j i^iYh af/ifan^e fivm leaa/lnq edge . Sirtgfe sfotfeif ^ f1api£f,o'joc,-o.B^. NACA ACR No. L5C08 Fig. lib '-//Vo 4- 1 1 , f~^N y/c, 0.3/ 1 /r"^ 11 P> /' ~^ CON 'IDEljlTIAL 1 1 ^ \. / ^ j>V / N n\ // \ ^v n - V J y/c 7/ /Y^ -^■i '// =—: ^ &> // '^i^ 1 ^ \ \ V / £ -S f4 S .6 O / £3 4 S .6 U/Vo '-- y/c. .6 / _^ ,<\ p=: :^ ^ / / N nN / \ N / \ s..^ 1 ^ y y/c^.5/ s^ I t \ :^ — i^ V ^ \ ^^ i\ ^: J O / .2 .3 4 S 6 O ./ .2 3 •? .5 6 UM . ^ ^J t (> =^ ^ If -<^ ^- V i ' N ^■^ J ^ y en lit UMIT lONAlJ EE f< AOVI R AEfi ORY INAUT CI j .5 / ,? J <» .J" .« D/s/once fn:>rn /eading edge^ x/c i^/V^ 1 _ _ y/c,.^o^ // > ■n-v - 1 =^ ""-v .. -1 - 1 1 -^:-^ //I ' ■ i H ^ 1 i M j i i^ i i ! coNlraENraL 1 , O / ^ -! ■« J" 6 O/i/a/icc fron/ /crjrM/icr edge . •%: O .50 /■OO (b) Vo, tl6 m//es per /:Our (appro x.). FiO'/re. //. - Continued. NACA ACR NO. L5C08 Fig. lie i.a "A 'o .4- - 1. 1 t 1 ;oNfii)ENri*L /n. f^ l^. y/c, o.ai / \ ^ k ' \^ ^ ^ \\N, ^\ '// \\ 1 K jj ■■ 1 1 ^t, 0.7/ ir N ^ - - ^ f \ ^> '*N i' \ 1 \ 1 /// k^d V \j O V z J .4- jT .6 U/Vo ,4. .2 Wr, .6 / r -~ ^ ^ ^ 1 ^ V , ^ % I S ^ ■ — 7 -- ■^ J -- / ,2 .5 J 1 \ Vt - u/V, Dii/c/tKC ferrn /cji.:/ing eji^ej Vr. c ^ y/c, .51 ( ~~~^ S \ / \ 2= S^ ^!s // J^^ '/ s V jj O ./ .£ J -4 .£' .6 ^. y/c,.t o If ■^ k < C1 N ■ 1 -> / ~s ^ j\ V 1 ■^ CO MMITT UNAL FE fO AtR( bur »«1IT CS O I £ 3 4 S C D/sfance from /eac/iny <^dge^ Vc O .15 .50 k) l/oj 60 /I i/e-i f(?r hour (Opprox.), hqure //■ - Condurjecl. NACA .014 ACR No L5C0e F ig . 12 .010 I .oce. .000 ,004- CON-IDEIjiriAl i- — J — Y S _ X — • — -X — +— -X— — -(-'■ Spanai/se sfcff/On) y/Cj O.FiO .O/d .0/6 .0/4 .o/d ■§.0/0 , ^. .00s- 1 .000 ■^ .004 . ^y Vo (mph) 33 46 + 66 X ^+x'' r ,)C-' +" -^ rx J i — -x" ^ ^ Propeller removed 5paHi8 + j ^ X ^ ^ '^ ^^ -^ ' V ^ ' ^ .^x ^ .o>z ^ ^sT :='-^- _^ ,x^ ■^ .0/0 ( 3 — s: ^^^^Propeller remoi/ed .003 .006 5paHi^/:se sfcff/'or?,y/Cj .S-O lOMM UIUN riEE LAb OR A ISURV RON* IIICS . .ooz CONf^lDENriAl _-j 1 o ,/ .z /.o I.I 12 .3 .4 .5 .& .7 .3 .9 rhru^st d/sk-loadlng coefflcienfj 72 Fiaure IZ -Va rial lor) of .^ec/lor) profile -drag coefficient u/lfh propeller ihrusf ^coefficient Sngle .-^lolfea flapicff, C° cC,-O.Z°,- 0^^,0.11. UNIVERSITY OF FLORIDA 3 1262 08104 975 UrjIVERSITY OF FLORIDA DOCUMENTS DEPARTMENT GAINESVILLE. FL 3261 1-7011 USA