Abstract
A Gurney flap is a simple passive flow control device that, when employed on wings, can significantly augment its lift with minor changes in drag and stall angle. In this work, a Gurney flap of height 0.02c was employed on low-AR flat plate wings (AR ≤ 1.5) of different planforms (rectangular, Zimmerman and inverse Zimmerman). Measurements were carried out at a low Reynolds number (1 × 105) to understand the flap's influence on the flow field over the wings. Time-averaged 2D particle image velocimetry (PIV) measurements on the wings' mid-span plane revealed a leading-edge separation bubble. The early reattachment of the leading edge separated flow is consistent with the results obtained from surface oil flow visualization. Stereoscopic-PIV measurements carried out at different cross-flow planes showed an increase in the strength of wingtip vortices and higher downwash for the Gurney flapped configuration. The collective information from these measurements suggests that the Gurney flap increases the strength of wingtip vortices via enhanced pressure difference between the upper and lower surface of the wing. The strong wing tip vortices promote higher downwash between them that reattaches the separated shear layer leaving a leading-edge separation bubble in between. The increased downwash delays complete flow separation to higher angles of attack. The strong tip vortices retain the lift-generating vortical flow closer to the wing. Hence, the maximum lift coefficient and stall angle were significantly increased.
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Data and material are available on request to the corresponding author.
Abbreviations
- AR:
-
Aspect ratio
- b :
-
Wing span, m
- c :
-
Wing root chord, m
- C D :
-
Drag coefficient
- C L :
-
Lift coefficient
- D :
-
Drag, N
- h :
-
Height/size of Gurney flap, m
- L:
-
Lift, N
- Re:
-
Reynolds number
- U α :
-
Freestream velocity, m∕s
- u :
-
Streamwise velocity, m∕s
- v :
-
Vertical velocity, m∕s
- α :
-
Angle of attack, deg
- ω x :
-
Streamwise vorticity, 1∕s
- ω z :
-
Spanwise vorticity, 1∕s
References
Albertani R (2008) Wind-tunnel study of gurney flaps applied to micro aerial vehicle wing. AIAA J. https://doi.org/10.2514/1.35110
Anyoji M, Nonomura T, Aono H, Oyama A, Fujii K, Nagai H, Asai K (2014) Computational and experimental analysis of a high-performance airfoil under low-Reynolds-number flow condition. J Aircr. https://doi.org/10.2514/1.C032553
Baker JP, Standish KJ, van Dam CP (2007) Two-dimensional wind tunnel and computational investigation of a microtab modified airfoil. J Aircr. https://doi.org/10.2514/1.24502
Bragg MB, Heinrich DC, Balow FA (1996) Flow oscillation over an airfoil near Stall. AIAA J 34(1):199–201. https://doi.org/10.2514/3.13045
Broeren AR, Bragg MB (1998) Low-frequency unsteadiness during airfoil stall and the influence of stall type. In: 16th AIAA applied aerodynamics conference, Albuquerque, NM, U.S.A. AIAA-98–2517 https://doi.org/10.2514/6.1998-2517
Broeren AR, Bragg MB (2001) Spanwise variation in the unsteady stalling flowfields of two-dimensional airfoil models. AIAA J. https://doi.org/10.2514/2.1501
Buchholz MD, Tso J (2000) Lift augmentation on delta wing with leading-edge fences and gurney flap. J Aircr. https://doi.org/10.2514/2.2710
Chen H, Chen B (2022) Lift enhancement of tiltrotor wing using a gurney flap. Int J Aerosp Eng 2022:1245484. https://doi.org/10.1155/2022/1245484
Chen H, Qin N (2017) Trailing-edge flow control devices for wind turbine1performance and load control. Renew Energy 105:419–435. https://doi.org/10.1016/j.renene.2016.12.073
Chen ZJ, Qin N, Nowakowski AF (2013) Three-dimensional laminar-separation bubble on a cambered thin wing at low Reynolds numbers. J Aircr 50(1):152–163. https://doi.org/10.2514/1.C031829
Choudhry A, Arjomandi M, Kelso RM (2015) A study of long separation bubble on thick airfoils and its consequent effects. Int J Heat Fluid Flow 52:84–96. https://doi.org/10.1016/j.ijheatfluidflow.2014.12.001
Cole JA, Vieira BAO, Coder JG, Premi A, Maughmer MD (2013) Experimental investigation into the effect of gurney flaps on various airfoils. J Aircr 50(4):1287–1294. https://doi.org/10.2514/1.C032203
Coton FN, Galbraith RA (1999) An experimental study of dynamic stall on finite wings. Aeronaut J 103(1023):229–236. https://doi.org/10.1017/S0001924000027895
Crompton B (2000) Investigation of the separation bubble formed behind the sharp leading edge of a flat plate at incidence. Proc Inst Mech Eng, Part G: J Aerosp Eng. https://doi.org/10.1243/0954410001531980
Daniel L, Traub LW (2013) Effect of aspect ratio on gurney-flap performance. J Aircr. https://doi.org/10.2514/1.C032140
DeVoria AC, Mohseni K (2017) On the mechanism of high-incidence lift generation for steadily translating low-aspect-ratio wings. J Fluid Mech. https://doi.org/10.1017/jfm.2016.849
Giguere P, Dumas G, Lemay J (1997) Gurney flap scaling for optimum lift-to-drag ratio. AIAA J 35(12):1888–1890. https://doi.org/10.2514/2.49
Gordnier RE, Attar PJ (2014) Impact of flexibility on the aerodynamics of an aspect ratio two membrane wing. J Fluids Struct. https://doi.org/10.1016/j.jfluidstructs.2013.10.004
Graham M, Muradian A, Traub LW (2018) Experimental study on the effect of gurney flap thickness on airfoil performance. J Aircr. https://doi.org/10.2514/1.C034547
Greenwell DI (2010) Gurney flaps on slender and nonslender delta wings. J Aircr. https://doi.org/10.2514/1.46610
Hansen KL, Kelso RM, Choudhry A, Arjomandi M (2014) Laminar separation bubble effect on the lift curve slope of an airfoil. 19th Australasian Fluid Mechanics Conference, Australasian Fluid Mechanics Soc, Melbourne, Australia, pp 1151–1154. https://hdl.handle.net/2440/92003
He X, Wang J, Yang M, Ma D, Yan C, Liu P (2016) Numerical simulation of Gurney flap on SFYT15 thick airfoil. Theor Appl Mech Lett 6:286–292. https://doi.org/10.1016/j.taml.2016.09.002
Hoerner SF (1965) Fluid-Dynamic Drag.
Jang CS, Ross JC, Cummings RM (1998) Numerical investigation of an airfoil with a Gurney flap. Aircr Des 1(1998):75–88. https://doi.org/10.1016/S1369-8869(98)00010-X
Jeffrey D, Zhang X, Hurst DW (2000) Aerodynamics of gurney flaps on a single-element high-lift wing. J Aircr 37(2):295–301. https://doi.org/10.2514/2.2593
Jeffrey DRM, Hurst DW (1996) Aerodynamics of the Gurney flap. AIAA-96–2418-CP. https://doi.org/10.2514/6.1996-2418
Kline SJ, McClintok FA (1953) Describing uncertainties for single sample experiments. Mech Eng 75(1):3–8
Lee T (2009) Aerodynamic characteristics of airfoil with perforated gurney-type flaps. J Aircr 46(2):542–548. https://doi.org/10.2514/1.38474
Lee M, Ho C (1990) Lift force on delta wing. Appl Mech Rev 43:9. https://doi.org/10.1115/1.3119169
Li Y, Wang JJ (2003) Experimental studies on the drag reduction and lift enhancement of a delta wing. J Aircr 40:2. https://doi.org/10.2514/2.3120
Li YC, Wang JJ, Tan GK, Zhang PF (2002) Effects of Gurney flaps on the lift enhancement of a cropped non slender delta wing. Exp Fluids. https://doi.org/10.1007/s003480200010
Li Y, Wang JJ, Zhang P (2003) Influences of mounting angles and locations on the effects of gurney flaps. J Aircr 40(3):494–498. https://doi.org/10.2514/2.3144
Liebeck RH (1978) Design of subsonic airfoils for high lift. J Aircr 15(9):547–561. https://doi.org/10.2514/3.58406
Lin JCM, Pauley LL (1996) Low-Reynolds-number separation on an airfoil. AIAA J. https://doi.org/10.2514/3.13273
Linehan T, Mohseni K (2019) Investigation of sliding alula for control augmentation of lifting surfaces at high angles of attack. Aerosp Sci Technol 87:73–88. https://doi.org/10.1016/j.ast.2019.02.008
Maughmer MD, Bramesfeld G (2008) Experimental investigation of gurney flaps. J Aircr 45(6):2062–2067. https://doi.org/10.2514/1.37050
McGranahan BD, Selig MS (2003) Surface Oil Flow Measurements on Several Airfoils at Low Reynolds Numbers. 21st AIAA Applied Aerodynamics Conference, Orlando, Florida. AIAA 2003–4067. https://doi.org/10.2514/6.2003-4067
Meena MG, Taira K (2018) Airfoil-wake modification with gurney flap at low Reynolds number. AIAA J 56:4. https://doi.org/10.2514/1.J056260
Meyer R, Hage W, Bechert DW (2006) Drag reduction on gurney flaps by three-dimensional modifications. J Aircr. https://doi.org/10.2514/1.14294
Mueller TJ (1985) The influence of laminar separation and transition on low Reynolds number airfoil hysteresis. J Aircr. https://doi.org/10.2514/3.45199
Mueller TJ (2001) Unsteady stalling characteristics of thin airfoils at low Reynolds number. Fixed Flapping Wing Aerodyn Micro Air Vehicle Appl. https://doi.org/10.2514/5.9781600866654.0191.0213
Mueller TJ, Batill SM (1982) Experimental studies of separation on a two-dimensional airfoil at low Reynolds numbers. AIAA J. https://doi.org/10.2514/3.51095
Myose R, Papadakis M, Heron I (1998) Gurney flap experiments on airfoils, wings, and reflection plane model. J Aircr. https://doi.org/10.2514/2.2309
Pauley LL, Moin P, Reynolds WC (1990) The structure of two-dimensional separation. J Fluid Mech. https://doi.org/10.1017/S0022112090003317
Pohlen LJ, Mueller TJ (1984) Boundary layer characteristics of the Miley airfoil at low Reynolds numbers. J Aircr. https://doi.org/10.2514/3.45011
Ripley MD, Pauley LL (1993) The unsteady structure of two-dimensional steady laminar separation. Phys Fluids a: Fluid Dyn. https://doi.org/10.1063/1.858719
Selig MS, Guglielmo JJ, Broern AP, Giguere P (1996), Experiments on airfoils at low reynolds numbers, 34th aerospace sciences meeting and exhibit, AIAA Paper, 1996–0062. https://doi.org/10.2514/6.1996-62
Smith JA, Pisetta G, Viola IM (2021) The scales of the leading-edge separation bubble. Phys Fluids 33:045101. https://doi.org/10.1063/5.0045204
Solovitz S, Eaton J (2004) Dynamic flow response due to motion of partial-span gurney-type flaps. AIAA J. https://doi.org/10.2514/1.1200
Souppez JRG, Bot P, Viola IM (2021) On the Effect of the Leading-Edge Separation Bubble on the Aerodynamics of Spinnakers. 7th High-Performance Yacht Design Conference, Auckland. https://hal.archives-ouvertes.fr/hal-03661052
Standish KJ, van Dam CP (2005) Computational analysis of a microtab-based aerodynamic load control system for rotor blades. J Am Helicopter Soc 50:249–258. https://doi.org/10.4050/1.3092861
Swanson T, Isaac KM (2010) Planform and camber effects on the aerodynamics of low-Reynolds-number wings. J Aircr 47(2):613–621. https://doi.org/10.2514/1.45921
Taira K, Colonius T (2009) Three-dimensional flows around low-aspect-ratio flat-plate wings at low Reynolds numbers. J Fluid Mech. https://doi.org/10.1017/S0022112008005314
Torres GE, Mueller TJ (2004) Low-aspect-ratio wing aerodynamics at low Reynolds numbers. AIAA J. https://doi.org/10.2514/1.439
Traub LW (2009) Effects of Gurney flaps on an annular wing. J Aircr 46(3):1085–1088. https://doi.org/10.2514/1.43096
Traub LW (2017) Examination of gurney flap pressure and shedding characteristics. J Aircr 36(4):1990–1995. https://doi.org/10.2514/1.C034279
Traub LW (2019) Effect of plain and gurney flaps on a nonslender delta wing. J f Aircr 56:2. https://doi.org/10.2514/1.C034929
Traub LW, Agarwal G (2007) Exploratory investigation of geometry effects on gurney flap performance. J Aircr 44(1):351–353. https://doi.org/10.2514/1.28385
Traub LW, Freienmuth EO (2011) Effect of streamwise attachment gap on aerodynamic characteristics of gurney flaps. J Aircr 48:1. https://doi.org/10.2514/1.C031226
Traub LW, Galls SF (1999) Effects of leading- and trailing-edge gurney flaps on a delta wing. J Aircr 36:4. https://doi.org/10.2514/2.2507
Troolin DR, Longmire EK, Lai TW (2006) Time-resolved PIV analysis of flow over a NACA 0015 airfoil with gurney flap. Exp Fluids. https://doi.org/10.1007/s00348-006-0143-8
Van Dam CP, Yen DT, Vijgen PMHW (1999) gurney flap experiments on airfoil and wings. J Aircr 1999:484–486. https://doi.org/10.2514/2.2461
Visbal M, Garman DJ (2019) Dynamic stall of a finite-aspect-ratio wing. AIAA J. https://doi.org/10.2514/1.J057457
Visbal M, Yilmaz TO, Rockwell D (2013) Three-dimensional vortex formation on a heaving low-aspect-ratio wing: computations and experiments. J Fluids Struct 38:58–76. https://doi.org/10.1016/j.jfluidstructs.2012.12.005
Wang Z, Gursul I (2017) Lift enhancement of a flat-plate airfoil by steady suction. AIAA J 55(4):1355–1372. https://doi.org/10.2514/1.J055382
Wang JJ, Zhan JX, Zhang W, Wu Z (2006) Application of a Gurney flap on a simplified forward-swept aircraft model. J Aircr 43(5):1561–1564. https://doi.org/10.2514/1.20283
Wang JJ, Li JC, Choi KS (2008) Gurney flap—lift enhancement, mechanisms and applications. Prog Aerosp Sci 44:22–47. https://doi.org/10.1016/j.paerosci.2007.10.001
Yilmaz TO, Rockwell D (2010) Three-dimensional flow structure on a maneuvering wing. Exp Fluids 48:539–544. https://doi.org/10.1007/s00348-009-0772-9
Yilmaz TO, Rockwell D (2012) Flow structure on finite-span wings due to pitch-up motion. J Fluid Mech 691:518–545. https://doi.org/10.1017/jfm.2011.490
Zhan JX, Wang JJ (2004) Experimental study on gurney flap and apex flap on a delta wing. J Aircr. https://doi.org/10.2514/1.4044
Zhang K, Hayostek AM, He W, Theofilis V, Taira K (2020) On the formation of three-dimensional flows over finite-aspect-ratio wings under tip effects. J Fluid Mech 895:2020. https://doi.org/10.1017/jfm.2020.248
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This work was carried out purely on academic interest without funding from external sources. The authors are very grateful to the head of the division, Dr. L. Venkatakrishnan, for supporting such efforts in the lab.
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Arivoli, D., Singh, I. Effect of Gurney flap on the vortex-dominated flow over low-AR wings. Exp Fluids 64, 68 (2023). https://doi.org/10.1007/s00348-023-03605-y
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DOI: https://doi.org/10.1007/s00348-023-03605-y