1、m . -NATIONALADVISORYCOMMITTEEFOR AERONAUTICSTECHNICAL MEMORANDUMNo. 1095-?IND-rummLMOTIONINVESTIGATIONOF THE HORIZONTALOF A WING NEAR THE GROUND ,BY Y, M. Serebrisky and S. A. BiachuevCentral Aero-HydrodynemicalInstitute,.,WashingtonSeptember,l$346 (2A LIBRARYANtikWMEMoRIAL AmOhwn!xcmLM30RATORYLang
2、leyField,VA!k Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NATIONAL ADVISORY COXP!ITT3E FOR AERONAUTICS. , . TECHNICAL MEMORANDUM No. 1095WIND-TUNNl!lLINVESTIGATION 02?THE HORIZONTALMOTION OF A WING NEAR THE GROUND1By Y. M, Serebrisky and S. A. Bi
3、achuevBY the method of images the horizontal steady motion ofa wing at small heights above the ground was investigated inthe wind tunnel, A rectangular wing with Clark Y-H profilewas tested with and without flaps. The distance from thetrailing edge of the wing to the ground was varied withinthe limi
4、ts 0.75 ; -overAn.alycausewingaa.cbI.vPx(a-pHs,wing together with the nea.surement of lift, drag, andt of longitudinal stability the pressure distributionthe wing section near the ground also was found.“sis of the pressure distribution curves explains thes of the cha.nqe in aerodynamic characteristi
5、cs of theat horizontal steady flight near the ground.NOTATIONangle of attack of wingangle cf attack corresponding to zero liftwing chordwing spanratio Of K,aXiiliU1;thickness of profile to chordsspect rr.ti.oof wingaagle of deflection of flapvelocity of un+.isturbed flw in wind tunnel or flightveloc
6、ity of airnlanei;ass density of z,irdistance along chord from leaciing edgetangent of an:le of inclination of lift curve fora wing cf infinite spannonililensional pressure coefficientdistance froti the axis of bound vertex of wing to grounddistance from triling edge of wing to grounddistance from tr
7、ailing edge of flap to groundlocal ncrual fnrce coefficientlCJCP.1 1101m?lfOrCEj coefficient fOr 10Wer Surface fIfprofile3Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-c Zu local ncrnal force coefficient for upper surface ofprofileat w ngle of .tta
8、ckof lower winga,Uw angle of attack of upper wingTEST PROCEDUREIn the CAHI T-5 wind tunnel having an open-work sectionand a flirileterof the jet at the work section of 2.06 milli-meters ests were conducted by the method of images on aodel of-a-riectangul,ar wing. Two identical wing models1000 by 200
9、 millimeters were repared. A Cl(ark Y-H profilewith relative thickness h = 0.12 was chosen. One of thenodels (the lower one) was suspended on a six-componentbalance, the other (the upper) was not connected with thesuspension system. The upper wing was located with respectto the lower wing as require
10、d by the method of images, thatis, such that the upper and lower wings formed a symmetricalsystem witkl respect to n center plane passing between themcorresponding to the plane on the ground. For the test aspecial setup was used that had been previously applied inthe investi,tion of the case cf grea
11、t height abcve the ground.(See zeference 3.) The lower win 0.5 this chnge is very smalland may be essentially neglected. This shows that for thesedist.iices aoove the ground the effect of the profile thick-ness is S:iall. Furthermore, with decrease in the distance2s the displaceient cf the anle of z
12、ero lift beins toincrea._serapidly and for $ = C.125 for the given profile:ifiedi,atelypreceding the start of sepe.-a-ticn, there is a very considerable increase in the lift: “(C) At suall va,lue of CL ,ith decrease in s there isa,cnsiderz,ble incre.se in the deriv+.ve d% /da and, forexampl for CL =
13、 (3Cfor ; = 0.25, d-LE- = 7.96, while forthe isolated wing z = 3.73.(d) For = 4 - 12 the increase in the lift force coefficient ACL depends little on the angle of attack.Below is given the mean values of the increments in theabove-mentioned range of angles of attack:.-, = .-. .- -. .,-, .- _c 0.75 0
14、.175 there is a.smalldecrease in C1max. This drop at comparatively large distances has been confirr.edby a large number of other tests.(See references 5 and 3; ) During the flow of air be-tween. the wing and the grcund there is an increase of pres-sure at the lower surface of the profile, and for ve
15、ry smalldistances this incree.se in pressure is very large. Atmediufi angles f attack it leads directly to a gener(al increase in the lift. Simultaneously, however, with an in-crease in the pressure at the lower surface there is a.decrease in the pressure at the upper surface near the leadingedge an
16、d an increase in the unfavorable pressure gradientwhich leads to an earlier flow separation near the ground.At relatively large distances (: 5 0.175) the increasein pressure on the lower surface cannot entirely compensatefor the sharp increase in pressure at the upper surface due -to the early separ
17、ation and for this reason a sLall drp incLlax is obtained. If the distances are small, however,(: The coefficient 5 on the lowersurface a%taine lare negative vr,lues.0IJxauin,ntion of figures 16 and 17 (a = 6 nnd 10) permitsdrtawiil.:an irt,portantccnclusin. It is enera.lly assui!edthfit the effect
18、!,fnearness to the r,un is equivalent tr,achnqc in the true :ngle of stteck. This conclusion is.arriveclat f-!11,?,na.lyzing, by the iiethdofiii,ciges,the curves,ger and lower surfaces than on increasing the angleof attack. On the upper surface for these angles of attackthe pressure chgnges are insi
19、gnificant and consist mainly c!fa decrease in p nen,r the leading edge and an increase in near the trailing edge. Over the entire lower surface thereis a very considerable increzse ifipressure. Thus , it isseen thet the ground effect must not be cvnsiflered as equiva-lent to a chane in the true angl
20、e of attack. AKreement inthe value of the lift with the formulas taking account onlyof the effect of the vortex sheet of the upper wing (referent. esProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TM No. 10956 and 3) may be expected only for the
21、 case of large distances 1), where in general the changes in the aerodynamic,Char.Cteristl cs zre not large. Thus , even for the approximateconputatlon of the chanCT, the finiteness of the chordand!-the thickness of the profil= must be taken into account.The computations given in the appendix show i
22、hat this nay ledone with sufficient accuracy only for :3. As regardsthe change In the drag for nA it is necessary to take3into account only the induce: drag. For below-sthlling anglesof attack good qualitative agreement is obtained.I?igure 18 (a = 14) confirms what has been remarkedaboe with regard
23、to the change in CLma in horizontalsteady flight near the ground. It is seen on this figure thatpremature flow separation is obtained on the upper surfacew“hile on the lower surface there is a very sharp increase inpressure. YGr + o,175 this increase in the pressure canIIOt compensate ior th loss o-
24、fldue o T.5.0.5the agreement obtained is satisfactory. For a,o thevalues of H are greater than the corresponding values of s.24It may be shown that for the computation by formula (1)gives satisfactory results.On the same figures is given the coninutation according toWi.eselsberger in whi.c,haccount
25、was tkeri only of the c.rrec-tion ACLl (dobted. curve). Bad agreeaent wzs bt%ted. The formula ofWiese!.sberger may bs used only for 1.The correction on the tin+:for ground effect is ve difficult toobtain in the cafleof small le?Lts above the FYJLlrldat ne:tied s”llpositive anes (in thi car.e40.5 the
26、agreement of the computation byformula (5) withcex.periment for below-ste.lling angles issufficiently close.For the case of the wing with flap the derivation of thegenerl relations offers great difficulties. Here are givenempirical formulas obtained on the basis of the a;nalysis ofthe reslts of the
27、test described above. They are tnue forEf = 60 for angles of attack below stalling.0.145 -Q-%ACL = -.-0.275;+ 110.155 :-aoo = CD 1- -0.41 : + 1516f = 60(7)IIorthe test here described these formulas give good agreement.Trnslation by S. Reiss,National Advisory Committeefor Aeronautics.REFEREITCESXk Se
28、rebrisky, Y, M: The Effect on the Increase of the LiftCoefficient in the Rotational Motion of a Wing.Technika Vozdushnogo Flota No. 11, 1936.18., .,. -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TM 0. 10952. Serebrisky, Y. M: Experimental In
29、vestigation of theVertical Approach of a Plate and the Inclined Approachof a Wing to the Ground. CAHI Rep. No. 422, 1939.3* Serebrisky, Y. M; The Effect of the Hearness to theGround on the Aerodynamic Characteristics of an Air-plane. CAHI Rep. No. 26?, 1936.4. Silverstein, Abe, and White, James A.:
30、Wind-Tunnel Interferenee with Particular Reference to Off-Center Posi-tions of the Wing and to the Downwash at the Tail.NACA Rep. No. 547, 1935,5. Tani, Itiro, Taima, Masuo, an Simidu, iSodi:, The Effectof Ground on the Aerodynamic Characteristics of aMonoplane Wing. Rep. of the A.R,I., Tokyo Imperi
31、alUniversity, No. 156, (vol. 13, no. 2) 1937.6. Wieselsberger, C: Wing Resistance near the Ground. NACATM No, 77, 1922.7. Wenzinger, Carl J. : Pressure Distribution over a ClarkY-H Airfoil Section with a Split Flap. NACA T!i No.627, 1957.“TBIBLIOGR2.PEIYD5twyler, G.: Untersuchung iiber das Verhalten
32、. von trag-fli.igelprofilen sehr nahe am Boden. Mitteilungen ausdeni Institut fur Aerodynamic, Eidgendssiche TechnischeHochschule (Ziirich) 1934.Tomotika, Susumu, Nagamiya, Takeo, and Takenouti, Yositada:The Lift on a Flat Plate Placed near a Plane Wall$ withSpecial Reference to the Effect of the Gr
33、cund upon theLift of Monoplane Aerofoil. Rep. of the A.R.I., TokyoImperiel University, No. 97, (vol. 8, no. 1) 1933.IJshakov, B. A.: Effect of Nee,rness to the Ground on theAerodynamic Characteristics of the Wing. CAHI Tech,Note No. 47, 1935.19Provided by IHSNot for ResaleNo reproduction or networki
34、ng permitted without license from IHS-,-,-H-1-H+PtI Ij#IH I I I I I I I I Io z- I I a o#O#/,I44Fig.1Fig.245%;.Fig.3IProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-II. LL_-_-.- .-d “ - 9e?- -r -q5A,$,- nm.x“91009a71b-t 25.o Iil?ig.5 *“U1.Provided by
35、IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-INACA TM No. 1095 Figs. 6,7,8,9Fig.6,I , , 1 1 1 ! I 1 I I I I IFig.9Fig.7Fig.8Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.qI!izFig.11Provided by IHSNot for Re
36、saleNo reproduction or networking permitted without license from IHS-,-,-NACA TM No. 1095 Figs. 12,13,14,.,./0 d“Fig.12 Fig.13 (3J)a u.oFig.14Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NA(IATM NO. 1095*F-4-3-0?-1nu+.4xFig.1SFig.16Provided by IHS
37、Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-rly .1!II,J ml I I I I I I ! ! I I 1 I I I 1 1 1 III4 I r ,1 1 1OLsfo” L&so” I I,I I I I I 1,. I i ttttttll-x liiii NsL_il., ,L1 1 IXn.v. “o .zAm,Fig.17 Fig.18 ti.P-I“Provided by IHSNot for ResaleNo reproduction or ne
38、tworking permitted without license from IHS-,-,-twFig.20 .Fig.19Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. NACA TM No. 1095 Figs. 21,22,-,., ,.,9.Fig.21Fig.22Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-P-84-3-.240n*iFig.23rl-lmllll 111111z-9sml%”liiiilli IP! I I04d AA+.x:01a71 4Xx7-0 4Fig.24Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
