1、=my IhJFOR copy 24,- - - “-gz2Em!DEmi_xc=rRM A51J11;-= . - -.-=:=”c-”F !3.-.-.-.-=.-:, _*-+- . _- . LlsRESEARCH MEMORANDUMTHE EFFECTS AT TRANSONIC SPEEDS OF THICKENING THETRAILING EDGE OF A WING WITII A 4-PERCENT-THICK CIRCULAR-ARC AIRFOILBy Joseph W. Cleary and George L. StevensAmes Aeronautical La
2、boratoryMoffettField, Calif, -?Nassificationcane.ld(IXchanudtof.4)ByAutho:i #A TsGhL!.b.A,.!:.:.w:.:cQ:.!A?!.!t1. d (q. ,“yFflzfw. BY- . *r. -m:., .(-A K GRADE OF OFFICLii “hIAit “ANGE). . .M.4. .w CMSSEZ6DDwuMcwr-Em%!?iizs:e=zwNATIONAL ADVISORY COMMITTEEFOR AERONAUTICSWASHINGTONDecember 11, 1951.-
3、_ -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY KAFB, NM. llllllll!llllltllllllllllllllllll=“”:-“3IUCAFMA51JZl !EEzEzEE owqi15 - .:NATIO ADVIEX2RYCOMZMEE TOR AERONAUTICSRESEARCH MEMORANDUM-1.EEEEECTSAT TRANSONIC SPEEDS CD?THICKENING T
4、HETRKILIRGEX+EOFAWWA- THICK C3RCUIAR=KBC AIRFOILBy Joseph W. C!learyand George L. StevensSUMMARY.The effects of a systematicvariation of trailingdge thicknessof a symmetrical circ c airfoil on the aer nmbe of some practical value at.both subsonic _. .and supersonicMach nrmbers. .The present investig
5、ationwas undertaken to evaluate the effect , .ofan increase in trailing+dge thickness on the aerodynamic character-istics of a thin three-dimensionalwing in the transonic Ich numberrange. For this investigationthe thick trailing+dge airfoils wereformed by building up the trailhg edge to the desired
6、thickness andthen fairing to the origtil afoil by straight lines. The forwardportion of the ctrculararc section remained intact and the resulting -airfoil was not one of the optimum sections.derived in reference 1.-drag c.oeffickntlift coefficientNOTATION(twtbe semisnan aqs whereas tlat of the wedge
7、 airfoil of thesame thickness continued to increase. In the present case, a comparisonof the Mft-curve sopes of an NACA 63A.004airfoil of the same phn form .and aspect ratio (reference) with those of the 0.3 arid0,6 blunt-trailindge airfoils of circular-arc origin shows similar values oflift-curve s
8、lope in the transonfcMach number range. Thus it appears wthat while increases in lift-curve slope can be expected by increasingthe trailing-edge thickness of circular+rc airfoils, the markedimprovement in lift+urve slope of blunt-trailing-edgeairfoils overconventionalairfoils indicatedby references
9、2 and 4 would not occurin the transonic range for airfoil thicknesses of the order of 4 percent.The effect of increasing the trailing-edge thickness of conventionalairfoils was not considered in the present Investigationbut the resultsof reference 6 show tkt for a 10-percentAhick conventionalairfoil
10、,increasing the trailing-edge thickness increases the live slope. ,Althougha sufficientlyhigh angle of attack was not reached at.=the higher Mach numbers to show the effect of trailing+dge thicknesson maximum lift coefficient,the data do indicate progressively higher maximum lift coefficientsas the
11、trailingAge thictiesswas increasedat 0.60,Mach number. The effect of surface rouglmess on the lift char-.acteristics appeared”practically negligible except for slightly lowermaximum lift coefficients for the various airfoils at 0.60 Mach number, Aw1Provided by IHSNot for ResaleNo reproduction or net
12、working permitted without license from IHS-,-,-. (NACA RM A51Jll 7PitChin hence, the pressure drags of the blunt airfoilswould be expected to be higher than the pressure drag of the circular-arc airfoil. .As the fre=tream Mach nzmiberand also the Reynolds nuuiberwasincreased through the transonic rm
13、ge, a decrease in base=pressurecoefficient occurred at speeds approximately corresponding to the drag-divergenceMach nwiber. This trend is shown in figure 14 for the inner-most base=pressure measuring station. This decrease prohbly resultswhen a supersonic ension occurs around the sharp corner of th
14、s %lunttrailing edge. The magnitude of this expansion is detemninedby theshape of the wake and Is sufficient to result in a low pressure whichwas about perc”mt of the free-stream static pressure for the blunttrailing edge with a thiclmess ratio of 1.0. With increasingMachnuniber,the lwse-pressure co
15、efficients increased and the base pressurewas approxitely 40 percent of the free+ tream static pressure up tothe highest speeds of the test for this airfoil.A spanwise gradient of base pressure was found to exist asindicated in figure 15. This gradient,with increasingpressure fromroot to tip, could
16、be partially due to the velocity gradient over thebump normal to the bump surface; however, this variation was not aslarge as the snwise gradient of base pressure. . The variation of base-pressure coefficientwith angle of attack forthe smooth airfoils with various.trailing-edgethiclmessesand at thed
17、ifferent spanwise stations is shown in,figure 13(a). At low subsonicspeeds the minimum base-pressure coefficient occurred at zero angle ofattack. At transonic speeds the trendsbaseressure coefficientwith changingThe effect of surface roughness oncomparison of figures is(a) and 13(bj.face roughness c
18、aused the base-pressureindicated essentially a constantangl.e.ofattack.the base pressme is shown by aIn general, the addition of sur-trends to be more consistent.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-C-ring the rough condition with the smoo
19、th condition indicates that . roughness increased the base yressure and delayed the negative peak ofbasepressure coefficientsat transonic speeds to a higher Mach nmiber.These trends are shown in figure 14. The minimum drag was higher forthe airfoils with surface roughness, indicating that any decrea
20、se ofbase dragby the additicm of surface roughness was more tti canceledby increased friction and (2) insufficientdata were obtained to make a statisticalanalysis o? the variation ofwake fluctuationwith angle of attack.At hw SdS (M= 0.60)thewake total-pressure fluctuationsincreased markedly with inc
21、reasing trailing-edge thickness. The dis-turbeaces set w in the wake were probably sufficiently strong to causean teady circulation to be eskblished around the airfoil, resultingin unsteady forces and, hence, some buffeting.lnvestition of figure 19 shaws that the wake fluctuationsbehindthe airfoils
22、having O and 0.3 trailing-edge thiclmesseswere relativelysmll at luw speeds, increased gradually to a peak of 0.25q at a Mechnu?iberofl0.90, and then decreased slightly. The wake fluctuationsbehind the airfoil with 0.6 trailingdge thickness renmined.practicallyconstant up to 0.90 Mach nuniberand the
23、n increased sharply. The airfoilhavinga trailingdge thickness of 1.0 hd a wake fluctuation of 0.69qat 0.60 Mach ?nmiber,decreased to a minimum of 0.31q at 0.92 Machnumber, and then increased sharply again as the speed was furtherincreased.In general, t“heblunt=trailing-edgeairfoils had larger wake f
24、luc-tuations tkn the basic circular-e.rcairfoil and it also appears fromthis test (see fig. 20) that increasing the trailing-edge thictiessabove O.0 of the maximum thickness results in relatively large wake totil=pressure fluctuations even at low speeds and hence increases thepossibility of buffetin
25、g.The effectof boattailing the blunt tmiling edge was to decreasethe amplitude of the wake total=pressure fluctuationas comparedwiththe amplitude behind the 1.0 blunt-trailing-edgeairfoil at most speedsand also indicated lower amplitudes at Mach nunbers greater than 0.90as compared with the 0.6 blun
26、t-trailing+dge airfoil. Boattailingappears to offer a practical means of reducing the total-pressure fluc-tuations in the wake and hence the possibility of buffeting of blunt-trailing-edge airfoils.L. . .=-. .-+. .b - - - .Provided by IHSNot for ResaleNo reproduction or networking permitted without
27、license from IHS-,-,-NACA RM A51Jll.11CONCLUDING KWARICS.T 5667, I?eb. 9, 1948. a71.-.- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA RM AUll._J, : -mNmEmpL4flF-13Figure l.- Typical model mounted on the transonic bump.Provided by IHSNot for Re
28、saleNo reproduction or networking permitted without license from IHS-,-,-14 . -1-, FenceNACA RM A51Jll.Figure 2.-Dimensionsof theredungukvwings.“, -.5.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA RM A51%U -a 15.“,Leudingedge f, 0.04cforoUy h,
29、 0.3 tI ,#po.5oc-4 =Bodtoiled airfoil-4cJF”Figure 3.- Airfoil profiles.0.6/.ot0.6mm?iz?i-”Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2.2#2./.ffl/.8/.7/.6.5 .6 .7 .8 .9 /.0 /./ 1.2Mach number, M “vFigure 4.- Variation of Reynold% number with Mach
30、 numbe.,1“”: I i,bProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACARM A51%U.20./0./0o17.70 80 90 /00 /0 /20Bump station, inch es =29=Figure 5.- Typical Mach number contours of the Ames16-foot wino-tupn el fransonic bump.+!oti :.Provided by IHSNot
31、for ResaleNo reproduction or networking permitted without license from IHS-,-,-PCn1.0.8.6-.4-.6I A I d III-4 0 4 8 12 16 for M, 0.60Angle of attack, a, dega) c b% u.Figure 6. Aerodynamic characteristics at various MOCh numbers. CkUfO$-OrC Pro fife, # O.Provided by IHSNot for ResaleNo reproduction or
32、 networking permitted without license from IHS-,-,-#1.0.8.6-.4-,6I tI 1 II 1-1 Iw=i Ihl I I 1. I I I II Io .04 .08 ,12 .16 .20 .24 for M, 0.60Drag coefficient. co(b) CL VS CDFigure 6,- Continued1 ,“ IProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-It
33、)o1.0.8.6so4.2-.4-.6t-H o Without surface roughnessA With surface roughnessI I. tll El.04 0 .04 -.08 for M, 0.60Pitching-moment coefficient,(c) GLVS CmFigure 6. Concluded.,* !, , f: 1c.J,Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ic!i0fEl1;!ji.1
34、.0.6-.2-.4-.6-4 0 4 8 12 16 for M, 0.60Angie of attack, a, dog(0) CL w aFigure Z Aerodynamic characteristics at various Mach numbers. Biunt -trai/ing-edge profiie, n 0.30.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1.0.Provided by IHSNot for Resa
35、leNo reproduction or networking permitted without license from IHS-,-,-. , 6,1.0.8.6Qj .4-.2-.40 .04 .08 .f2 .16 .20 .24 .28 for M, 0,60Drag Coefficient CDb) c W coFigure 8.-Continued., ,Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.08 -.12 -.16 f
36、or A4,0.60Pitching-moment coeff/cien C(C C VScmFigure 8.-Concluded.: ,. .,-r.!:, .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-J1.0.8.6Q“-.2-,4,-404 8 12 16 for M, 0.60Angle ofatfack, a, deg(a) CL vs uFigure 9.- Aerodynamic characteristics of vari
37、ous Mach numbers. Blunt-trailing-edge profile, S 1.00.3Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-n)(n1.0.8,1,1“Ii.6-.2-.40 Without surface roughness., a With surface roughness.6o 4II I I I I I I I I I lb IProvided by IHSNot for ResaleNo reprodu
38、ction or networking permitted without license from IHS-,-,-, . ,1.0.8.6u“-.2w v M i I IP.4 I I I I I I I 7 I AI I I 1/ Ir =5=.04 0 ,-.04 :08 -. ;2 for M, 0.60Pitching-moment coefficient, Cm(c) CL Vs cmFigure 9.-Conciuded.Ii. ,.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
