NASA-TM-X-3166-1975 Low-speed wind-tunnel investigation of forward-located spoilers and trailing splines as trailing-vortex hazard-alleviation devices on an aspect-ratio-8 wing mod.pdf

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1、ANDNASA TECHNICAL NASA TM X-3166MEMORANDUMI(NASA-TM-X-3166) LOW-SPEED WIND-TUNNEL N75-15608INVESTIGATION OF FORWARD-LOCATED SPOILERSAND TRAILING SPLINES AS TRAILING-VORTEXSHAZARD-ALLEVIATION DEVICES ON AN UnclasASPECT-RATIO-8 WING MODEL (NASA) 26 p HC H1/01 09157LOW-SPEED WIND-TUNNEL INVESTIGATIONOF

2、 FORWARD-LOCATED SPOILERS ANDTRAILING SPLINES AS TRAILING-VORTEXHAZARD-ALLEVIATION DEVICESON AN ASPECT-RATIO-8 WING MODELDelwin R. CroomLangley Research Center 0OWT0Hampton, Va. 23665NATIONAL AERONAUTICS AND SPACE ADMINISTRATION * WASHINGTON, D. C. * FEBRUARY 1975Provided by IHSNot for ResaleNo repr

3、oduction or networking permitted without license from IHS-,-,-1. Report No. 2. Government Accession No. 3. Recipients Catalog No.NASA TM X-31664. Title and Subtitle 5. Report DateLOW-SPEED WIND-TUNNEL INVESTIGATION OF FORWARD- February 1975LOCATED SPOILERS AND TRAILING SPLINES AS TRAILING-VORTEX HAZ

4、ARD-ALLEVIATION DEVICES ON AN ASPECT-RATIO-8 WING MODEL7. Author(s) 8. Performing Organization Report No.Delwin R. Croom L-989210. Work Unit No.9. Performing Organization Name and Address 505-06-22-01NASA Langley Research Center 11. Contract or Grant No.Hampton, Va. 2366513. Type of Report and Perio

5、d Covered12. Sponsoring Agency Name and Address Technical NoteNational Aeronautics and Space Administration14. Sponsoring Agency CodeWashington, D.C. 2054615. Supplementary Notes16. AbstractAn investigation was made in the Langley V/STOL tunnel in order to determine, bythe trailing-wing sensor techn

6、ique, the effectiveness of either a forward-mounted spoileror a tip-mounted spline as trailing-vortex attenuation devices on an unswept aspect-ratio-8wing model.The trailing-wing rolling-moment data taken in the tunnel diffuser section show goodagreement with the data taken in the tunnel test sectio

7、n. This agreement indicates thatreasonable results may be obtained in the Langley V/STOL tunnel in experimental investi-gations of the trailing-vortex hazard at relatively great distances behind aircraft models.17. Key Words (Suggested by Author(s) 18. Distribution StatementVortex alleviation Unclas

8、sified - UnlimitedTrailing-vortex hazardSTAR Category 0119. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price*Unclassified Unclassified 26 $3.75For sale by the National Technical Information Service, Springfield, Virginia 22151Provided by IHSNot for R

9、esaleNo reproduction or networking permitted without license from IHS-,-,-LOW-SPEED WIND-TUNNEL INVESTIGATION OFFORWARD-LOCATED SPOILERS AND TRAILING SPLINES ASTRAILING-VORTEX HAZARD-ALLEVIATION DEVICES ON ANASPECT-RATIO-8 WING MODELDelwin R. CroomLangley Research CenterSUMMARYAn investigation was m

10、ade in the Langley V/STOL tunnel in order to determine, bythe trailing-wing sensor technique, the effectiveness of either a forward-mounted spoileror a tip-mounted spline as trailing-vortex attenuation devices on an unswept aspect-ratio-8 wing model.The trailing-wing rolling-moment data taken in the

11、 tunnel diffuser section show goodagreement with the data taken in the tunnel test section. This agreement indicates thatreasonable results may be obtained in the Langley V/STOL tunnel in experimental inves-tigations of the trailing-vortex hazard at relatively great distances behind aircraft models.

12、At distances up to 100 wing-chord lengths downstream of the model without flaps (ata lift coefficient of 0.5), the trailing-wing rolling-moment coefficients were reduced byabout 25 percent when either the forward-located outboard spoiler or the trailing splinewas used as a vortex-alleviation device.

13、 Beyond 100 chords downstream the effective-ness decreased and at about 160 chords downstream there was no effect of either device.For the model with a single-slotted flap (at a lift coefficient of 1.25), the forward-located midspan spoiler produced about a constant 25-percent reduction of the trail

14、ing-wing rolling-moment coefficient at downstream distances up to 180 chords, which was thelimit of the investigation. In contrast, the spline reduced the trailing-wing rolling momentvery little in the near field, but it did become more effective with increasing downstreamdistances. At 180 chords do

15、wnstream, about a 20-percent reduction in the trailing-wingrolling-moment coefficient was obtained.INTRODUCTIONThe strong vortex wakes generated by large transport aircraft are a potential haz-ard to smaller aircraft. The National Aeronautics and Space Administration has beenrequested by the Federal

16、 Aviation Administration to determine the feasibility of reducingthis hazard by aerodynamic means.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Previous work (ref. 1) has shown that the magnitude of the vortex-wake hazard isgreatly influenced by th

17、e direction of the flight of the aircraft which is penetrating thetrailed vortices. As discussed in reference 1, a cross-track penetration at right anglesto the trailing vortices tends to cause pitching and vertical motion and to produce verticalloads on the penetrating airplane in a manner similar

18、to that of a gust encounter. Also,an along-track penetration, parallel to and between the wing-tip vortices, can occur inboth the take-off climbout and the landing approach and may cause settling or, at least,may reduce the rate of climb of the penetrating aircraft. However, an along-track pene-trat

19、ion through the vortex center is considered to be the most hazardous encounter sincesuch penetration would induce a rolling motion to the penetrating aircraft that couldresult in an upset.One approach in assessing the trailing-vortex hazard is to determine the velocityprofile of the vortex and, by i

20、ntegrating the velocity profile over the span of the penetrat-ing aircraft, the induced rolling moment can be inferred. Detailed measurements of thevelocity profile through the trailing vortex have been obtained by the use of attitude sensorvanes and total-pressure probes (ref. 2), yawheads (ref. 3)

21、, tuft grids (ref. 4), vortexmeters (ref. 5), and hot-wire anemometers (ref. 6).Another approach in assessing the trailing-vortex hazard is to simulate an airplaneflying in the trailing vortex and to make direct measurements of the individual rollingmoments. Therefore, a sensor technique which allow

22、s direct measurements of the rollingmoment induced by the trailing vortices from a lifting airplane model on a model mounteddownstream at various distances was developed in the Langley V/STOL tunnel.The purpose of this investigation was to use the direct measurement technique in theLangley V/STOL tu

23、nnel in order to determine the induced rolling moment on a trailingmodel in the near and far field caused by the trailing vortex generated by an aspect-ratio-8wing model, and also to determine the effectiveness of either a forward-located spoiler ora trailing drag device (hereafter referred to as a

24、spline) as a vortex hazard-alleviationdevice.SYMBOLSAll data are presented with respect to the wind axes. The pitching-moment coeffi-cients are referred to the quarter chord of the wing mean aerodynamic chord.b wing span, mCD drag coefficient, DragqSM2Provided by IHSNot for ResaleNo reproduction or

25、networking permitted without license from IHS-,-,-CL lift coefficient, LiftqSMTrailing-wing rolling momentCl1 trailing-wing rolling-moment coefficient,TW qSTwbTwCm pitching-moment coefficient, Pitching momentqSMCMc wing chord, mwing mean aerodynamic chord, mq dynamic pressure, N/m2S wing area, m2Y,Z

26、 lateral and vertical dimensionsa angle of attack, degSubscripts:M aspect-ratio-8 modelTW trailing wingMODEL AND APPARATUSSketches of the aspect-ratio-8 vortex-generating models are shown in figure 1.Two sizes of vortex-generating models were used during this investigation. One had aspan of 2.438 m

27、and was tested in the rear and forward bays of the V/STOL tunnel. (Seefigs. 2 to 4.) The other had a span of 1.219 m and was tested in the forward bay of theV/STOL tunnel. (See figs. 4 and 5.) Each of the vortex-generating model wings wasunswept and had an aspect ratio of 8, a taper ratio of 1, and

28、an NACA 0012 airfoil section.For some of the tests, a 30-percent-chord, three-quarter-span, single-slotted flap, whichhad an NACA 0012 airfoil section, was installed as shown in figures 1 and 5. Details of thespoilers and the trailing drag device (spline) are given in figure 1.The trailing-wing mode

29、ls had a span equal to one-quarter of the span of thegenerating-model wings, a chord equal to 30 percent of the chord of the generating-modelwing, and an NACA 0012 airfoil section.3Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The Langley V/STOL tu

30、nnel has a test-section height of 4.42 m, a width of 6.63 m,and a length of 15.24 m. The vortex-generating models were sting supported on a six-component, strain-gage balance system which measured their forces and moments. Theangle of attack was determined from an electrical inclinometer mounted in

31、the fuselage.The trailing models were mounted on a single-component, strain-gage roll balance, whichwas attached to a traverse mechanism capable of moving the model both laterally andvertically. (See fig. 6.) The lateral and vertical positions of the trailing model weremeasured by electrical potenti

32、ometers. This entire traverse mechanism could be mountedto the tunnel floor at various tunnel longitudinal positions downstream of the vortex-generating model, as shown in figure 4.TESTS AND CORRECTIONSVortex-Generating ModelsAll tests were run at a free-stream dynamic pressure in the tunnel test se

33、ction of430.90 N/m2 which corresponds to a velocity of 27.4 m/sec. The Reynolds numbers forthese tests were approximately 5.74 x 105 and 2.87 x 105, based on the chord of the largerwing and the smaller wing, respectively. The basic longitudinal aerodynamic charac-teristics were obtained through an a

34、ngle-of-attack range of approximately -40 to 130.Blockage corrections were applied to the data by the method of reference 7. Jet-boundary corrections to the angle of attack and to the drag were applied in accordance withreference 8.Trailing-Wing ModelThe trailing-wing model and its associated roll-b

35、alance system were used as a sen-sor to measure the induced rolling moment caused by the vortex flow downstream of thegenerating model. The trailing model was positioned at a given distance downstream ofthe generating model and the vortex-generating model was set at an angle of attack neces-sary to

36、provide the desired lift coefficient. With the tunnel operating at a low speed(q 5 200 N/m2), the trailing vortex was made visible by smoke which was ejected near thewing tip. (See fig. 2.) The traverse mechanism was positioned laterally and verticallyso that the trailing vortex was near the center

37、of the mechanism. The tunnel was thenbrought up to the test dynamic pressu-e and the trailing vortex was probed with the trail-ing model. A large number of trailing-wing rolling-moment data points (usually from 50to 100) was obtained from the lateral traverses at several vertical locations. From the

38、sedata, contour plots of constant rolling-moment coefficients were constructed as shown infigure 7. From contour plots such as these, the maximum rolling-moment coefficient andthe location of the vortex core relative to the generating wing were determined.4Provided by IHSNot for ResaleNo reproductio

39、n or networking permitted without license from IHS-,-,-Trailing-wing rolling-moment measurements were made at downstream distancesfrom 5 to 180 chord lengths behind the generating models. (See fig. 4.) A large portionof the trailing-wing rolling-moment data was obtained with the trailing model posit

40、ionedin the diffuser section of the V/STOL tunnel. These data were reduced to coefficient formbased on the local dynamic pressure at the trailing-model location. The vortex-core loca-tion relative to the wing tip of the generating model has been corrected in order to accountfor the progressively lar

41、ger tunnel cross-sectional area in the diffuser section.RESULTS AND DISCUSSIONVortex-Generating ModelThe longitudinal aerodynamic characteristics of the 2.438-m span model withoutflaps and with the three-quarter-span, single-slotted flaps installed are presented in fig-ures 8 and 9, respectively. Th

42、ese results indicate that the splines did not appreciablyalter the lift characteristics of the model. They act essentially as a pure drag deviceadding a constant increment of drag throughout the angle-of-attack range.These results also indicate that the forward-located spoilers act not only to produ

43、cedrag, but also to modify the lift characteristics of the model. The lift-curve slope wasreduced and the span-load distribution apparently was altered because of the forward-located spoiler.Trailing-Wing ModelThe position of the trailing vortex and the induced rolling-moment coefficient on thetrail

44、ing-wing model at various downstream distances behind the vortex-generating wingare presented in figures 10 and 11 for the wing without flaps and the wing with flaps,respectively. Each data point in figures 10 and 11 was obtained from contour plots suchas figure 7. These data were obtained from four

45、 different tests in the V/STOL tunnel.Two of the tests were for the 2.438-m-span vortex-generating model mounted in the rearbay. (See figs. 2 and 4.) The other two tests were for the 2.438-m-span and the 1.219-m-span vortex-generating models mounted in the forward bay. (See figs. 3 and 4.) Thesymbol

46、s at the bottom of these data figures (figs. 10 and 11) indicate the location of theaft end of the tunnel test section for each of these sets of data. The data at downstreamdistances greater than indicated by the bottom symbols are data obtained with the trailingmodel in the diffuser section of the

47、tunnel.By using the two sizes of models and testing them at the various tunnel locationsindicated in figure 4, a direct comparison of trailing-wing rolling-moment data obtainedin the tunnel test section can be made with trailing-wing rolling-moment data obtained inthe tunnel diffuser section.5Provid

48、ed by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-It can be seen in figures 10 and 11 that the values of the trailing-wing rolling-moment coefficients measured downstream of the vortex-generating model are generallylower when the large vortex-generating mode

49、l was mounted in the rear bay of the tunnelas compared with when the large vortex-generating model was mounted in the forward bayof the tunnel. These differences may be due to the two different model support systemsused during these investigations. (See figs. 2, 3, and 4.) The relatively small differencesnoted in the values of the trailing-wing rolling-moment coefficients measured downstream