1、.8?NATIONAL ADVISORY COMMITTEEJR AERONAUTICS -. . TECHNICAL NOTE.No. 1351JUL10 N47-.COMPARISON BETWEEN THE MEASURED AND THEORETICALSPAN LOADINGS ON A MODERATELY SWEPT-FORWARDAND A MODERATELY SWEPT-BACK SEMISPAN WINGBy Robert A. IvIendelsohn and Jack D. BrewerLangley Memorial Aeronautical LaboratoryL
2、angley Field, Va.a71WashingtonJuly 1947 ,Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.?yx:=Taper ratio . . . . . . . . . . 0.327Sweep of qm”rten-chord line, deg . ., -12Unifomn geometric twist (washout.),deg 0Root airfoil seotion . . . . . . . ,
3、, NACA blpTip airfoil section . . . ,.,; , . NACA 4412Installation and Tests. .wing Swept-back wing13 a71 5510,101.51 7.51“0:243 .2$NACA 44I.8NACA 4418.,.-. ,. Each model was mounted horizontally (with zero dihedral) on.the ,side support of the tunnel b,alenceframe, completely free from the .tunnel
4、wall except for a flexible sealused to prevent flow throughdthe gap between the tunnel wall and the wing support block. (See fig. 2.).In order to allow.movement ok the part of the wi”thatextended beyond the tunnel disk, the swept-forwardwing had a gap of approximately#inch left unmaledbetweenthe tun
5、nel wall and the rcot section,ehind,.the 67-percent.-chord-point. For the swept-backwing, slmil.argap wasleft unsealed forward of the 17-percent-ohd p?int. Check tests weremade on the swept-back wing to determine whether the fabricseal andopen gap affected the loading near the root section. For thes
6、e tests,plasteline was used to seal all gaps and to continue the wing contourto the tunnel wall.Because the wings were expeoted to deflect under load; a determina-tion of the wing twist was made. For the swept-forwardwing, the twistwas calculated by a method usi the measured spanloading and the know
7、nwing rigidity as determined from statfc tests. For the swept-back wing,the spanwise variation of twist.of the wfng under load was determinedby measuring the diplaoement of beamsof li q = 39.7”1/eqftU=+l.863C% -0.05; q=g8.3 lb/6gftcL = % . .CD = % t-0.01760%2.tCm. c% + 0.0013C %Provided by IHSNot fo
8、r ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN NO; 1351 7* Swe-back wing:u = + ld32Ck - 0002; q = 39.7 lb/sq fiwu = au + 0.923C%- 0.04; q = 98.3 lb/sq*,.,CL = C%CD = cm + 0.0173C%2 .cm=%where the subscript U denotes ticorrected values. The maxhnum%wist correctio
9、n near the tip at a dynamic,pressureof 98.3 pounds per squre foot and at an”angle of attack of 9 was0.54 for the swept-forwardwing and 0.77 for the swept-backwing,i-ATION OF RESULTS,Pressure distributions.-The measured section pressure distri-. butions are presented in figures 3 and 4. In order to o
10、btain a“%etterestimate of the pressure distributions corresponding to a rigid wingIn free air, cross plots of pressure coefficients at several chordwiselocations for each spanwlse station were madeagainst corrected angleof attack. From these plots, the parameters Pa and hence the local velocities ne
11、ar the rootregion were prpspmably changpd. Check tests on the swep-back winghaving plasteline to fair the wing contour to the tunnel wall indicatedthat, although the chdwise, pre,ssuredistribution was distorted bythe seal, the total load remained the same. The check tests alsoindicated that-very lit
12、tle loss in loading was caused by the chclearance gap between a part of the wing root and the tunnel wall and.that a distortion of the inboard load occurredwith a fabric seal regardless of whether it bulged into the air stream. ,v Span loading.- For the swept-fard wing, a comparison of the-measured
13、additional loading with the liftinhowever,a small basic loading was indicated by the measurements. This apparentbasic loading may be caused by construction irregularities,boundary-l.ayereffects, and errors in correcting for twist due to load.The results for the sweptAback wing show a loss in additio
14、nal loadnear the root similar to that found for the swept-forwa,rdwing. Thisloss was not shown by the full-span data of the tests described inthe appendix, even when the tunnel wall was simukted by B center platebut, since no measurements were made fortstations less than 0.10in that investigation, I
15、t is possible thatb.e loss in load occurred butwas not measured. For highly swept winge,semispan tests may give errorsin pitching mcznentabout the ae,rod-ic center because of distortionsin chordwise loading near the wing root and because,of changes in span. loading caused by tunnel-wall boundary-lay
16、er effects. Unpublished dataof the span loading over a twimensional wing completely spanning atunnel test section indicate that a loss in load of approximately5 percentmay have been caused a% section I by tunnel+alll boundary-wProvided by IHSNot for ResaleNo reproduction or networking permitted with
17、out license from IHS-,-,-10 NACA NO. 1351layer effects. The present swept-backlng tests indicate a higheroutbcanl loading than is shown by the tests described in the appendixor by liftinine or liftln,.i.Sncuded h fure 13(b) is a comparison between the”lift curvetaken from the data of the tests descr
18、ibed in the appendix and thepresent swept-back semispanwing tests. -d eent is sh”.Pressure integration for wing forces and momentsgave results which .compared very well with balance readings.yrofile-draa chara tec riatlc As shown in figure 14, the. measured.section profile4rag coeicients for the swe
19、pt-babk”wingare lowest near the center of the wing and increase as the dtstance “.from the center increases. If the variation in 10C gle of attackcausea by wing twist and the spanwise variation in Reynolmispen swept-wing models, one swept forward 12”and the other swept back 23 at the quarter-chord l
20、ine, in orderto detemine the spardoad distributions and to compare the experi-mental ana theoretical results. The full-span swept-back-w-model from which the semispan model was made was first testedin the Langley proyelleresearch tunnel in order to check thevalidity of the semispen tests.Provided by
21、 IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IWJATN No. 1371 .The results of these tests indioate the foULowi.ngccmclusims:1. Although the differences between span loadings determinedfrom tests in two wind tunnels weresma$l,they wereas great as the differeno
22、ee between span Jadings det.emuinedflxxaa lifting-line and lifting-surfacetheory, The theoretical curves approxi-mated the eerimental ones within the accurac required forengineering calculations2. A small loss ; “load,presuinablycaused by:the tunnel-wallboundary layer$ occurrednearthe root for both
23、semlspan wings.Becaqse.,$,t;s,loti,$?.ld apd because dietoti$na:M the chord-wise loadfhg”near the root, semispan tests of highly ewt wings maygive errorsIn pitching moment. *:.3. The aero the variation in jet-boundary induced angleacross the span was small enough to be neglected. A determinationof t
24、he section profile drag was made from wake profiles at a numberof spanwise stations 20 percent of the local wing chord behind thetrailing edge.The span loadings for the wing alone and for the wing equippedwith center plate and spoiler were determined for various anglesof attack. It was found that th
25、e spoiler extension which Mostclosely simulated the boundary layer for the semispan tests had verylittle effect on the basic or additional-load distribution. It isnoted that no pressure measurements were made on the inboard 10 percentof the span and that the load curve was extrapolated to zero slope
26、at the center of the wing.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.14 NAC!ATN NO. 1351REFERENCES *1. Swanson, Robert S., and Toll, Thomas A.: Jet-BoundaryCorrectionsfor Reflection-PlaneModels in Rectangul.qrWind Tunnele. ,NACAAX$R NO. 3E22, 1
27、943.2. Pearson, Henry A., and Jones, Robert T.: Theoretical Stabilityand Control Characteristics of Wings with Various Amounts ofTaper and Twist. NACA Rep. NO, .635, 1938.3. Anderson, Rtiond F.: Determination of the Characteristics ofTapered Wings. NACA Rep. No. 72, 1936.k. Cohen, Doris:, A Method f
28、or Determining the Cber and Twistof a Surface to Support a Given Distribution of Lift. NACA”TN No. 855, 1942.r. . . .,”Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. . 4 .IJUppof+ Lvk471a-lbs-xl6-M6-MUfw(+h Wd,uspd mlm, 6.10 ; fupefru?%,0.132z/6.7
29、2 J$?uvrefigure - De+od. of +he wtp+-mw nzdiif.L.K, Md. :2Lam.;.79-2*-3.27-3.71-3s-W9-3.s-3.75-s.-NATIM ADVISORYCmlm-m m MOuuTK.siRI$Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.- .-J2ctw 44!Ofi?c.? /ocd/or?$LA. DA. : 3.%SwM*4h) $wqof-buck W19; u
30、reammpb% W19), /3.55Jymre fief;Ospecffaflo,z5/ ; fuyw ridlo 0.243. NATIUW- ADV150RVmm-m R4 bJmwMn-q, 98.3 pounds per square foot.Figure 3.- Measured chordwise pressure distributions over a swept-forward-wing model.IProvided by IHS Not for ResaleNo reproduction or networking permitted without license
31、 from IHS-,-,-.- .0 .20 .40 .60 ,80 100Chordwue /bcaf/onlJ/c(a) Concluded.Figure 3.- Continued. b.II I.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. . , . .0 .20 .40 .60 .8o LOOchordwm kxalon,ltila, 0.5; q, 98.3 pounds per OquareFigure 3,- Contin
32、ued.foot.NA-mxlu A8n50RYculmnmmr.sm$.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.Sec+ion_D c 1?/ i /.1I;III0 0 00 .20 .40 .60 .80 Loo MTIONM. ADWSORYammnu Fm AEMnMmcsChordw/.se/ocahon,x/c(b) Concluded.Figure 3.- Continued.,!. * .IProvided by IHS
33、Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-. .r . , .-L?.80 .20 .40 .60 .80 00 MTlOWl MWSUWwmnl-mf m mmw-naChordwm /oca/on #(c) a, 4.0; q, 98.3 pounds per square foot.Figure 3.- Continued. %fi8Provided by IHSNot for ResaleNo reproduction or networking permitte
34、d without license from IHS-,-,-.80 .20 .40 .60 .80 /00 N4Tw ADVISORYCnnmll-m m AmmumcsChordw/. /OCQ+/Q?71 ,yic(c) Concluded.Figure 3.- Continued. . . . .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. . . .-20-/6.4.80 0 0 00 .20 .40 .60 ,80 KUChomk
35、.n? hcahw? , X/cd a, 10,9: q, 39.7 pounds per Bquare foot.Figure 3.- Continued.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. .- .-20“m%.4.8(d) Concluded.Figure 3.- Continued.,1 I “ -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
