REG NASA-N69-14762-1968 Wind tunnel investigations of vortex breakdown on slender sharp-edged wings.pdf

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1、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Final Report NASA Research Grant PJGR-I. 7-002 -043 WIND TUNNEL INTJESTIGATiGNS GF VORTEXBRFX KD OWN ON s LE NDER SHARP - E DGE 13 IV ETGS William H . Wentz, Jr . and David L. Kohlman University of Kans

2、as Center for Research, Inc. Engineering Sciences Division Report FRL 68-013 November 27, 1968 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-AC KNQWLEDGEMENTS The authors wish to express their appreciation to those who assisted in making this work

3、possible: to the National Science Fcilndation and the National Aeronautics and Space Administration for their financial support; especially to Mr. Mark Kelly, MASA rlmes Research Center, and Mr. Edward C . Polhamus, NASA Langley Research Center whc. made available to the author results of recent res

4、earch condmted at their re- spective offices; and to their able research assistant, Mr. Eennis Carinori, for his persev:.: ance . ii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Chapter TABLE OF CONTENTS Page I. INTRODUCTION 1 I1 . VORTEX BREAKDOW

5、N 4 Prior Experimental Investigations 4 Theoretical Considerations 5 I11 . SLENDER WING THEORY AND VORTEX LIFT rn . m 7 Lift . 7 Pitching Moment . 10 Drag . 10 IV . THE EXPERIMENTAL INVESTIGATION . 12 Test Facility 12 Test CQnditions . 12 Model qeometry . Delta Wings. 13 Model Geometry . Modified De

6、lta Wings 16 Flow Visualization Technique . 18 Force Measurements 19 Corrections . 19 V . RESULTS OF THE EXPERIMENTAL INVESTIGATIONS . 22 Vortex Breakdown at the Trailing Edge Chordwise Progression of Vortex Breakdown . Chordwise Progression of Vortex Breakdown . for Delta Wings. . 22 Delta Wings 26

7、 Modified Delta Wings . 28 Cropped Delta Wing . 28 Diamond and Arrow Wings 29 Double-Delta Wings . 29 Ogee Wing . 31 iii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Chapter Page Discussion of Force Characteristics. . 32 Lift and Pitching Characte

8、ristics . Lift and Pitching Characteristics . Delta Wings . 32 Modified Delta Wings . 36 Cropped Delta Wing 36 Diamond and Arrow Wings 37 Double-Delta Wings 38 Ogee Wing . Wind Tunnel Results . . 39 Ogee Wing . Compgrisons with Flight Test 40 Drag Due to Lift . Delta and Modified Delta Wings . 41 VI

9、 . CONCLUDING REMARKS . 44 REFERENCES . 46 FIGURES. . 49 iV Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-LIST OF FIGURES Figure 1 2.1 2.2 2.3 2.4 2.5 2.6 2.7 3.1 3.2 3.3 4.1.1 4.1.2 4.1.3 4.2 4.3 4.4 4.5 Page Tabulated Model Geometry. . . . . . .

10、. . . . . 49 Model GeQmetry - Delta Wings. . . . . . . . . 50 Model Geometry - Cropped 60 Delta Wing . . . . 51 Model Geometry - 70 Arrow Wing . . . . . . . . 51 Model Geometry - 70 Diamond Wing . . . . . . 52 Model Geometry - 7So/65O Double-Delta Wing. . , 52 Model Geometry - 80/65 Double-Delta Win

11、g, . . 53 Modal Geometry - Ogee Wing. . . . . . . . . 53 Model Installation Photos . . . . . . . . . e 54 Effect of Roughness Qn Breakdown Characteristics - (72.5O Delta Wing) . . e . 55 Vortex Breakdown Photos - 75/65 Double-Delta Wing, . . . . . . . . . . . . , 57 Vortex Breakdown Position - Delta

12、 Wings . . . . 59 Comparison of Vortex Breakdown Results With Comparison of Vortex Breakdown Results With Effect of Edge Shape on Vorkex Breakdown - Previously Published Data - 70 Delta Wing . 60 Previously Published Data - 65 Delta Wing . 61 60 Delta Wing . . . . . . . . . . , . . . 62 Vortex Break

13、down Position - Cropped 60 Delta Wing . . . . . , . . . . . . . . . . . 63 Vortex-Breakdown Position - 70 Arrow? Delta, and Diamond Wings . . . . . . . . . 64 Vortex Breakdown Position - 75/65 Double-Delta Wing. . . . . . . . . . . . . . 65 V Provided by IHSNot for ResaleNo reproduction or networkin

14、g permitted without license from IHS-,-,-Figure 4.6 4.7 5.1.1 5.1.2 5.2.1 5.2.2 5.3.1 5.3.2 5.4.1 5.4.2 5.5.1 5.5.2 5.6.1 5.6.2 5.7.1 5.7.2 5.8.1 5.8.2 5.9.1 5.9.2 Page Vortex Breakdown Position . 80/65“ Double-DeJta Wing 66 Vortex Breakdown Position . Ogee Wing . . 67 Lift and Pitching Characterist

15、ics . 45“ Delta Wing 68 Drag Due tq Lift . 45“ Delta Wing . 69 Lift and Pitching Characteristics . 50“ Deltawing. 70 Drag Due to Lift . 50 Delta Wing . 71 Lift and Pitching Characteristics . 55“ Delta Wing . 72 Drag Due to Lift . $5“ Delta Wing . 73 Lift and Pipching Characteristics . 60“ Delta Wing

16、 . 74 Drag Due to Lift . 60“ Delta Wing . 75 Lift and Pitching characteristics . 65“ Delta Wing 76 Drag Due to Lift. . 65“ Delta Wing . . 77 Life and Pitching characteristics . 57.5“ Delta Wing . 78 Drag Due to Lift . 67.5“ Delta Wing 79 Lift and Pitching Characteristics . 70 Delta Wing . 80 Drag Du

17、e to Lift . 70“ Delta Wing . 81 Lift and Pitching Characteristics . 72.5O Delta Wing 82 Drag Due to Lift . 72.5“ Delta Wing 83 Lift and Pitching Characteristics . 75“ Deltawing . 84 Drag Due to Lift . 75“ Delta Wing . 85 5.10.1 Lift and Pitching Characteristics . 77.5. Delta Wing . 86 vi Provided by

18、 IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Page Figure 5.10.2 5.11.1 5.11.2 5.12.1 5.12.2 5.13.1 5.13.2 5.14.1 5.14.2 5.15.1 5-15.2 5.16.1 5.16.2 5.17.1 5.17.2 5.18.1 5.18.2 5.19.1 5.19.2 5.20.1 5.20.2 Drag Dye to Lift - 77.5O Delta Wing 87 Lift and Pitchi

19、ng Characteristics - 80 Delta Wing . 88 Drag Due to Lift - 80 Delta Wing . 89 Lift and Pitching Characteristics - 82.5O Delta Wing . 90 Drag Due to Lift - 82.5O Delta Wing 91 Lift and Pitching Characteristics - 85O Delta Wing . 92 Drag Due to Lift - 85 Delta Wing . 93 Lift and Pitching Characteristi

20、cs - Cropped 60 Delta Wing . 94 Drag Due to Lift . Cropped 60 Delta Wing . 95 Lift and Pitching Characteristics - 70 Arrowwing. 96 Drag Due to Lift - 70 Arrow Wing . 97 Lift and Pitching characteristics - 70 Diamond Wing 9 8 Drag Due to Lift - 70 Diamond Wing . e . . 99 Lift and Pitching Characteris

21、tics - 75O/65O Double-Delta Wing. .loo Drag Due to Lift - 75O/65O Double-Delta Wing. .lo1 Lift and Pitching Characteristics - 8Oo/65O Double-DeJta Wing. .lo2 Drag Due to Lift - 8Oo/65O Double-Delta Wing. ,103 Lift and Pitching Characteristics - Ogee Wing, -104 Drag Due to Lift - Ogee Wing. .lo5 Effe

22、ct of Edge Shape on Lift and Pitching Characteristics - 60 Delta Wing . .lo6 Effect of Edge Shape on Drag Due to Lift - 60 Deltawing .lo7 vii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Figure Page 5.21 Lift and Drag Comparisons With Flight Test

23、Data . Ogee Wing . -108 6 Effect of Sweep on Vortex Breakdown at Trailing Edge . Delta Wings . 109 7 Effect of Sweep on Vortex Breakdown Position . Delta Wings . 110 viii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-LIST OF SYMBOLS A BD b C - C cO

24、 cL cD i cD C DO cM cS q S TE c1 A aspect ratio, b2/S vortex core breakdown wingspan wing local chord wing mean geometric chord, IC dy/S wing reference chord (uqually cepterline) wing lift coefficient, and it has also been neglected in the attached flaw lifting Surface theories more applicable to lo

25、w aspect ratio wings, e.g., Multhopp (1). These attached flow theories are quite adequate even for slender wings at small angles of attack, but are not adequate for predicting the forces developed at higher angles of attack required for landing and takeoff. At the higher angles, leading edge separat

26、ion occurs, resulting in vortex sheets which roll up along the upper surface of the wing to form strong line vortices.streaming aft along each edge. The low pressure fields induced by these vortices act to provide additional lift, referred to as “vortex lift.“ The proportion of vortex lift to total

27、lift increases with angle of attack and sweep angle. For example, 1 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-vortex lift amounts t;a 50% of total lift for a 75“ delta wing at a total lift coefficient of 1.0. Various authors have undertaken the

28、oretical analyses to predict vortex lift. An inherent shortcoming of all the theoretical methods, however, is that they do not account for the “breakdown“ or “bursting“ of the leading edge vortex cores which occurs a+ high angles of attack. Thus, knowledge of the limitations of vortex flow (i.e., vo

29、rtex breakdown) is of great practical importance to the designer who uses the slender sharp-edged lifting surfaces which are required to obtain high performance at supersonic speeds. Analyses of the instabilities of a simple fluid vortex which lead to breakdown have been undertaken by various invest

30、igators (for example, References 2 and 3) using fluid dynamic theory. Such theoretical considerations have not yet reached a skate of sophistication which would permit their applicgtion to the general case of predicting breakdown of wing leading edge vortices. For the present it seems that one must

31、rely on experimental measurements for determining the onset of breakdown on wings. Several investigators have provided vortex breakdown information for particular wings, using dye in water or smoke in air to mark the vortex cores and, hence, to indicate the breakdown. of ipsight into the effects .of

32、 leading edge sweep, pressure gradients, etc., on the breakdown. Such investigations have provided a great deal Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3 Systematic investigations on a family of delta wings were conducted by Earnshaw and Lawf

33、ordl (4) for wings with leading-edge sweep angles ranging from 55 to 76O. In these tests vortex breakdown observations were conducted utilizing a small tuft on a probe. Tests reported by Werle (5, 6) show that a blockage in the flow field may influence vortex breakdown. Thus, there was some question

34、 as to whether the probe influenced the breakdown measurement6 of Earnshaw and Lawf ord . Poisson-Quinton avd his associates at ONERA (7) have correlated vortex breakdown observations from hydrodynamic flow visualization studies with measured vortex lift from wind tunnel tests. The published correla

35、tions are limited to a few configurations. In addition, they are based upon tests at differing Reynolds numbers with different models, different mounting systems, etc. The purpose of the present research was to provide a rather complete parametric investigation of vortex breakdown for sharp-edged de

36、lta Wings, and to obtain force measurements from these same, mogels in the same test facility in order to correlate force and flow field characteristics in the most direct manner possible. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CHAPTER I1 VO

37、RTEX BREAKDOWN Prior Experimental Observations The phenomenon of vortex core “breakdown,“ vortex “bursting“ or “explosion, has been observed by numerous investigators, and is indeed visible to the casual observer in certain instances. Vortex breakdown is an abrupt increase in the effective diameter

38、of the rotational core associated with the vortex. The high velocities and corresponding low pressures associated with the core of a real fluid vortex, prior to breakdown, frequently make it visible to the naked eye. In air this may occur under conditions of high relative humidity, leading to conden

39、sation of the water vapor within the vortex core. These condensation vortices are occasionally visible on delta wing aircraft. When this occurs, the break- down of the wing vortices appears as a flaring of the core into a trumpet-like shape at which point the vortex seems to disappear, due to turbul

40、ent mixing of the water vapor. Delta wing vortices may also become visible as cavitation regions in water at moderate pressures. Breakdown is dis- cernible as the termination of a cavitation filament in this case. This technique is simple and, to the authors knowledge 4 Provided by IHSNot for Resale

41、No reproduction or networking permitted without license from IHS-,-,-5 has not been used extensively for investigations of vortex breakdown. Investigators at ONERA in France (Poisson-Quinton, et al.) have developed a water tank facility to a high degree using colored dyes as tracers for vortex break

42、down studies. (See for example, Reference 7). Their investigations uti- lize models of small proportions (Reynolds numbers = 10 ). However, the results of these flow visualizations have been correlated with wind tunnel force tests conduc$ed at higher Reynolds numbers with impressive results (Referen

43、ce 8) . 4 Earnshaw (9) reported in 1964 on the use of a schlieren system in a subsonic wind tunnel to observe vortex breakdown. This work consisted of testing of 65 and 70 delta wings and some modified delta wings, and correlgtions of vortex breakdown results obtained from water tank tests. He pre-

44、sented data showing the progressive forward movement of the breakdown with angle of attack, and discussed the importance of using trip strips to stabilize the secondary separation at low Reynolds numbers. Theoretical Considerations Various investigators have attacked the problem of vortex breakdown

45、from a theoretical standpoint, utilizing viscous flow theory. These analyses have been restricted to the problem of a simple isolated line vortex of constant strength, and have not included the effects of a wing or a variable strength vortex (Such as is associated with a wing Provided by IHSNot for

46、ResaleNo reproduction or networking permitted without license from IHS-,-,-6 leading edge) . Kwan Lo So (10) has shown experimentally that as many as five different vortex flow regimes are possible in a simple conical diffuser, indicating the complexity of the vortex breakdown problem. Bossel and ot

47、hers (2) have shown theoretically that the maximum helix angle for stability of a vortex with an axial velocity is about 50. Unfoytunately, neither the core radius nor the vortex strength (circulation) is known in advance for wings. Thus, there is no method at present for applying this theoretical v

48、ortex stability criterion to a wing. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CHAPTER I11 SLENDER WING THEORY AND VORTEX LIFT Lift - Slender wing theory was developed in 1946 by R. T. Jones (ll), who adopted Munks slender body theory to the problem. For very slender wings (A 1) and small angles of attack, Jones theory predicts: More sophisticated attached flow 1 ftin