旋翼地面效应的气动建模与特性
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摘要
地面对旋翼气动特性影响明显,且导致旋翼流场更加复杂。为分析地面效应下的旋翼桨尖涡和流场变化特性,基于涡面和无滑移边界条件,求解第2类Fredholm方程获得地面涡面矢量分布,且将涡面矢量按涡扩散方程扩散到流体中,建立考虑黏性效应的地面气动模型,并耦合非定常面元/黏性涡粒子混合法以体现旋翼桨叶气动特性和旋翼尾迹的非定常效应,构建旋翼地面效应气动分析方法。通过计算Lynx尾桨地面效应下的性能和桨尖涡轨迹,并计算Maryland大学模型旋翼和NASA缩比旋翼地面效应下的垂向、径向速度分布,且与试验和CFD计算结果对比,验证了本文方法能较好捕捉地面效应下的旋翼尾迹变化特性和复杂速度场特性,且结果表明本文方法能较好模拟地面效应下旋翼桨尖涡的收缩、扩散、井喷、地面射流等物理现象。
The presence of a ground plane significantly alters the rotor aerodynamics and generates a more complex flowfield.To analyze the characteristics of the rotor tip vortices and flow-field in ground effect,aground aerodynamic model is then proposed based on the vorticity concept and no-slip boundary condition.In this model,the distribution of vorticity vector is solved through the second kind equation of Fredholm,and is diffused to the flow based on the diffusion equations,accounting for the viscous effects of the ground plane.An aerodynamic method of the rotor in ground effect is then established by coupling the ground aerodynamic model with an unsteady panel/viscous vortex particle hybrid method in which the unsteady aerodynamics of rotor and unsteady behavior of the rotor wake are taken into account.After then,the performance and geometry of tip vortex of Lynx tail rotor,vertical and radial velocities of a Maryland scaled rotor and NASA scaled rotor in ground effect are computed by the present method.Compared with the experiments and CFD results,the computed results show that the present method can capture the unsteady behavior of rotor wake and the complex flow-field of rotors in ground effect with high accuracy.Furthermore,the physical phenomena including the radial contraction and expansion of tip vortex,fountain flow,and wall jet of rotors in ground effect are captured by the present method.
The presence of a ground plane significantly alters the rotor aerodynamics and generates a more complex flowfield.To analyze the characteristics of the rotor tip vortices and flow-field in ground effect,aground aerodynamic model is then proposed based on the vorticity concept and no-slip boundary condition.In this model,the distribution of vorticity vector is solved through the second kind equation of Fredholm,and is diffused to the flow based on the diffusion equations,accounting for the viscous effects of the ground plane.An aerodynamic method of the rotor in ground effect is then established by coupling the ground aerodynamic model with an unsteady panel/viscous vortex particle hybrid method in which the unsteady aerodynamics of rotor and unsteady behavior of the rotor wake are taken into account.After then,the performance and geometry of tip vortex of Lynx tail rotor,vertical and radial velocities of a Maryland scaled rotor and NASA scaled rotor in ground effect are computed by the present method.Compared with the experiments and CFD results,the computed results show that the present method can capture the unsteady behavior of rotor wake and the complex flow-field of rotors in ground effect with high accuracy.Furthermore,the physical phenomena including the radial contraction and expansion of tip vortex,fountain flow,and wall jet of rotors in ground effect are captured by the present method.
引文
[1] MILLUZZO J I,LEISHMAN J G.Vortical sheet behavior in the wake of a rotor in ground effect[J].AIAA Journal,2017,55(1):24-35.
[2] SUGIURA M,TANABE Y,SUGAWARA H,et al.Numerical simulations and measurements of the helicopter wake in ground effect[J].Journal of Aircraft,2017,54(1):209-218.
[3] WADCOCK A J,EWING L A,SOLIS E,et al.Rotorcraft downwash flow field study to understand the aerodynamics of helicopter brownout[C]∥Proceedings of the American Helicopter Society Southwest Region Technical Specialists Meeting.Alexandria,VA:AHS,2008:1-27.
[4] PHILLIPS C,KIM H W,BROWN R E.The flow physics of helicopter brownout[C]∥Presented at the American Helicopter Society 66th Annual Forum.Alexandria,VA:AHS,2010:1273-1291.
[5] BETZ A.The ground effect on lifting propellers:NACATM-836[R].Washington,D.C.:NACA,1937.
[6] CHEESEMAN I C,BENNETT W E.The effect of the ground on a helicopter rotor in forward flight:R&M-3021[R].London:ARC,1955.
[7] ROSSOW V J.Effect of ground and/or ceiling planes on thrust of rotors in hover:NASA-TM-86754[R].Washington,D.C.:NASA,1985.
[8]何承健,高正.贴地飞行的旋翼尾迹研究[J].航空学报,1986,7(4):325-331.HE C J,GAO Z.A study of the rotor wake in nap of the earth[J].Acta Aeronautica et Astronautica Sinica,1986,7(4):325-331(in Chinese).
[9] DUWALDT F A.Wakes of lifting propellers(rotors)inground-effect:CAL BB-1665-S-3[R].Washington,D.C.:Cornell Aeronautical Laboratory,1966.
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[11] PRESTON J R,TROUTMAN S,KEEN E,et al.Rotorwash operational footprint modeling:RDMRAF-14-02[R].Middlesex:U.S.Army RDECOM,2014.
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[13] WACHSPRESS D A,WHITEHOUSE G R,KELLER J D,et al.A high fidelity brownout model for real-time flight simulations and tranners[C]∥American Helicopter Society 65th Annual Forum.Alexandria,VA:AHS,2009:1281-1304.
[14] SYAL M,LEISHMAN J G.Modeling of bombardment ejections in the rotorcraft brownout problem[J].AIAA Journal,2013,51(4):849-866.
[15] PHILLIPS C,BROWN R E.Eulerian simulation of the fluid dynamics of helicopter brownout[J].Journal of Aircraft,2009,46(4):1416-1429.
[16] ZHAO J G,HE C J.Physics-based modeling of viscous ground effect for rotorcraft applications[J].Journal of the American Helicopter Society,2015,60(3):1-13.
[17] GRIFFITHS D A,ANANTHAN S,LEISHMAN J G.Predictions of rotor performance in ground effect using a free-vortex wake model[J].Journal of the American Helicopter Society,2005,50(4):302-314.
[18]辛冀,李攀,陈仁良.地面效应中悬停旋翼的自由尾迹计算[J].航空学报,2012,33(12):2161-2170.XIN J,LI P,CHEN R L.Free-wake analysis of hovering rotor in ground effect[J].Acta Aeronautica et Astronautica Sinica,2012,33(12):2161-2170(in Chinese).
[19] LAKSHMINARAYAN V K,KALRA T S,BAEDER J D.Detailed computational investigation of a hovering microscale rotor in ground effect[J].AIAA Journal,2013,51(4):893-909.
[20] CROZON C,STEIJL R,BARAKOS G N.Numerical study of helicopter rotors in a ship airwake[J].Journal of Aircraft,2014,51(6):1813-11832.
[21]朱明勇,招启军,王博.基于CFD和混合配平算法的直升机旋翼地面效应模拟[J].航空学报,2016,37(8):2539-2551.ZHU M Y,ZHAO Q J,WANG B.Simulation of helicopter rotor in ground effect based on CFD method and hybrid trim algorithm[J].Acta Aeronautica et Astronautica Sinica,2016,37(8):2539-2551(in Chinese).
[22] TAN J F,WANG H W.Simulating unsteady aerodynamics of helicopter rotor with panel/viscous vortex particle method[J].Aerospace Science and Technology,2013,30(1):255-268.
[23]谭剑锋,王浩文,吴超,等.基于非定常面元/黏性涡粒子混合法的旋翼/平尾非定常气动干扰研究[J].航空学报,2014,35(3):643-656.TAN J F,WANG H W,WU C,et al.Rotor/empennage unsteady aerodynamic interaction with unsteady panel/viscous vortex particle hybrid method[J].Acta Aeronautica et Astronautica Sinica,2014,35(3):643-656(in Chinese).
[24]谭剑锋.直升机旋翼对尾桨非定常气动载荷的影响[J].航空学报,2015,36(10):3228-3240.TAN J F.Influence of helicopter rotor on tail rotor unsteady aerodynamic loads[J].Acta Aeronautica et Astronautica Sinica,2015,36(10):3228-3240(in Chinese).
[25] GREENGARD L,ROKHLIN V.A fast algorithm for particle simulations[J].Journal of Computational Physics,1997,135(2):280-292.
[26] KOUMOUTSAKOS P,LEONARD A,PEPIN F.Boundary conditions for viscous vortex method[J].Journal of Computational Physics,1994,113:52-61.
[27] PLOUMHANS P,DAENINCK G,WINCKELMANS G.Simulation of three-dimensional bluff-body flows using the vortex particle and boundary element methods[J].Flow,Turbulence and Combustion,2004,73:117-131.
[28] PONCET P.Topological aspects of three-dimensional wakes behind rotary oscillating cylinders[J].Journal of Fluid Mechanics,2014,517:27-53.
[29] COLAGROSSI A,GRAZIANI G,PULVIRENTI M.Particles for fluids:SPH versus vortex methods[J].Mathematics and Mechanics of Complex Systems,2014,2(1):45-70.
[30] PLOUMHANS P,WINCKELMANS G S.Vortex methods for high-resolution simulations of viscous flow past bluff bodies of general geometry[J].Journal of Computational Physics,2000,165:354-406.
[31] PLOUMHANS P,WINCKELMANS G S,SALMON J K,et al.Vortex methods for direct numerical simulation of three-dimensional bluff body flow:Application to the sphere at Re=300,500,and 1000[J].Journal of Computational Physics,2002,178:427-463.
[32] LIGHT J S.Tip vortex geometry of a hovering helicopter rotor in ground effect[J].Journal of the American Helicopter Society,1993,38(2):34-42.
[33] FILIPPONE A,BAKKER R,BASSET P M,et al.Rotor wake modelling in ground effect conditions[C]∥Presented at the 37th European Rotorcraft Forum,2011:29-40.
[34] LEE T E,LEISHMAN J G,RAMASAMY M.Fluid dynamics of interacting blade tip vortices with a ground plane[J].Journal of the American Helicopter Society,2010,55(2):22005-22116.
[35] RAMASAY M,YAMAUCHI G K.Using model-scale tandem-rotor measurements in ground effect to understand full-scale CH-47Doutwash[J].Journal of the American Helicopter Society,2017,62(1):1-14.
[2] SUGIURA M,TANABE Y,SUGAWARA H,et al.Numerical simulations and measurements of the helicopter wake in ground effect[J].Journal of Aircraft,2017,54(1):209-218.
[3] WADCOCK A J,EWING L A,SOLIS E,et al.Rotorcraft downwash flow field study to understand the aerodynamics of helicopter brownout[C]∥Proceedings of the American Helicopter Society Southwest Region Technical Specialists Meeting.Alexandria,VA:AHS,2008:1-27.
[4] PHILLIPS C,KIM H W,BROWN R E.The flow physics of helicopter brownout[C]∥Presented at the American Helicopter Society 66th Annual Forum.Alexandria,VA:AHS,2010:1273-1291.
[5] BETZ A.The ground effect on lifting propellers:NACATM-836[R].Washington,D.C.:NACA,1937.
[6] CHEESEMAN I C,BENNETT W E.The effect of the ground on a helicopter rotor in forward flight:R&M-3021[R].London:ARC,1955.
[7] ROSSOW V J.Effect of ground and/or ceiling planes on thrust of rotors in hover:NASA-TM-86754[R].Washington,D.C.:NASA,1985.
[8]何承健,高正.贴地飞行的旋翼尾迹研究[J].航空学报,1986,7(4):325-331.HE C J,GAO Z.A study of the rotor wake in nap of the earth[J].Acta Aeronautica et Astronautica Sinica,1986,7(4):325-331(in Chinese).
[9] DUWALDT F A.Wakes of lifting propellers(rotors)inground-effect:CAL BB-1665-S-3[R].Washington,D.C.:Cornell Aeronautical Laboratory,1966.
[10] FERGUSON S W.Rotorwash analysis handbook,volume I development and analysis:DOT/FAA/RD-93/31[R].Washington,D.C.:Federal Aviation Administration,1994.
[11] PRESTON J R,TROUTMAN S,KEEN E,et al.Rotorwash operational footprint modeling:RDMRAF-14-02[R].Middlesex:U.S.Army RDECOM,2014.
[12] QUACKENBUSH T R,WACHSPRESS D A.Enhancements to a new free wake hover analysis:NASA-CR-177523[R].Washington,D.C.:NASA,1989.
[13] WACHSPRESS D A,WHITEHOUSE G R,KELLER J D,et al.A high fidelity brownout model for real-time flight simulations and tranners[C]∥American Helicopter Society 65th Annual Forum.Alexandria,VA:AHS,2009:1281-1304.
[14] SYAL M,LEISHMAN J G.Modeling of bombardment ejections in the rotorcraft brownout problem[J].AIAA Journal,2013,51(4):849-866.
[15] PHILLIPS C,BROWN R E.Eulerian simulation of the fluid dynamics of helicopter brownout[J].Journal of Aircraft,2009,46(4):1416-1429.
[16] ZHAO J G,HE C J.Physics-based modeling of viscous ground effect for rotorcraft applications[J].Journal of the American Helicopter Society,2015,60(3):1-13.
[17] GRIFFITHS D A,ANANTHAN S,LEISHMAN J G.Predictions of rotor performance in ground effect using a free-vortex wake model[J].Journal of the American Helicopter Society,2005,50(4):302-314.
[18]辛冀,李攀,陈仁良.地面效应中悬停旋翼的自由尾迹计算[J].航空学报,2012,33(12):2161-2170.XIN J,LI P,CHEN R L.Free-wake analysis of hovering rotor in ground effect[J].Acta Aeronautica et Astronautica Sinica,2012,33(12):2161-2170(in Chinese).
[19] LAKSHMINARAYAN V K,KALRA T S,BAEDER J D.Detailed computational investigation of a hovering microscale rotor in ground effect[J].AIAA Journal,2013,51(4):893-909.
[20] CROZON C,STEIJL R,BARAKOS G N.Numerical study of helicopter rotors in a ship airwake[J].Journal of Aircraft,2014,51(6):1813-11832.
[21]朱明勇,招启军,王博.基于CFD和混合配平算法的直升机旋翼地面效应模拟[J].航空学报,2016,37(8):2539-2551.ZHU M Y,ZHAO Q J,WANG B.Simulation of helicopter rotor in ground effect based on CFD method and hybrid trim algorithm[J].Acta Aeronautica et Astronautica Sinica,2016,37(8):2539-2551(in Chinese).
[22] TAN J F,WANG H W.Simulating unsteady aerodynamics of helicopter rotor with panel/viscous vortex particle method[J].Aerospace Science and Technology,2013,30(1):255-268.
[23]谭剑锋,王浩文,吴超,等.基于非定常面元/黏性涡粒子混合法的旋翼/平尾非定常气动干扰研究[J].航空学报,2014,35(3):643-656.TAN J F,WANG H W,WU C,et al.Rotor/empennage unsteady aerodynamic interaction with unsteady panel/viscous vortex particle hybrid method[J].Acta Aeronautica et Astronautica Sinica,2014,35(3):643-656(in Chinese).
[24]谭剑锋.直升机旋翼对尾桨非定常气动载荷的影响[J].航空学报,2015,36(10):3228-3240.TAN J F.Influence of helicopter rotor on tail rotor unsteady aerodynamic loads[J].Acta Aeronautica et Astronautica Sinica,2015,36(10):3228-3240(in Chinese).
[25] GREENGARD L,ROKHLIN V.A fast algorithm for particle simulations[J].Journal of Computational Physics,1997,135(2):280-292.
[26] KOUMOUTSAKOS P,LEONARD A,PEPIN F.Boundary conditions for viscous vortex method[J].Journal of Computational Physics,1994,113:52-61.
[27] PLOUMHANS P,DAENINCK G,WINCKELMANS G.Simulation of three-dimensional bluff-body flows using the vortex particle and boundary element methods[J].Flow,Turbulence and Combustion,2004,73:117-131.
[28] PONCET P.Topological aspects of three-dimensional wakes behind rotary oscillating cylinders[J].Journal of Fluid Mechanics,2014,517:27-53.
[29] COLAGROSSI A,GRAZIANI G,PULVIRENTI M.Particles for fluids:SPH versus vortex methods[J].Mathematics and Mechanics of Complex Systems,2014,2(1):45-70.
[30] PLOUMHANS P,WINCKELMANS G S.Vortex methods for high-resolution simulations of viscous flow past bluff bodies of general geometry[J].Journal of Computational Physics,2000,165:354-406.
[31] PLOUMHANS P,WINCKELMANS G S,SALMON J K,et al.Vortex methods for direct numerical simulation of three-dimensional bluff body flow:Application to the sphere at Re=300,500,and 1000[J].Journal of Computational Physics,2002,178:427-463.
[32] LIGHT J S.Tip vortex geometry of a hovering helicopter rotor in ground effect[J].Journal of the American Helicopter Society,1993,38(2):34-42.
[33] FILIPPONE A,BAKKER R,BASSET P M,et al.Rotor wake modelling in ground effect conditions[C]∥Presented at the 37th European Rotorcraft Forum,2011:29-40.
[34] LEE T E,LEISHMAN J G,RAMASAMY M.Fluid dynamics of interacting blade tip vortices with a ground plane[J].Journal of the American Helicopter Society,2010,55(2):22005-22116.
[35] RAMASAY M,YAMAUCHI G K.Using model-scale tandem-rotor measurements in ground effect to understand full-scale CH-47Doutwash[J].Journal of the American Helicopter Society,2017,62(1):1-14.