共轴刚性旋翼悬停状态气动干扰机理
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摘要
建立了一个基于Navier-Stokes(N-S)方程的共轴刚性旋翼气动干扰数值模拟方法。应用运动嵌套网格技术模拟双旋翼反转运动。通过与试验值对比,验证了方法的有效性。分析了共轴刚性旋翼悬停状态的气动性能和流场特征,结果表明,双旋翼气动干扰主要来自4个方面:双旋翼尾迹涡相互诱导引起"涡诱导效应",使上旋翼气动性能优于下旋翼;双旋翼周期性相遇-离开过程中桨叶附着涡干扰引起"载荷效应",对应拉力周期性升降波动;双旋翼相遇时"厚度效应"使双旋翼拉力产生相反的脉冲波动;上旋翼尾迹涡与下旋翼桨叶碰撞引起垂直"桨-涡干扰效应",使下旋翼桨叶展向拉力分布受到干扰。
A numerical method based on Navier-Stokes(N-S) equations is developed to simulate the aerodynamic interaction of rigid coaxial rotor. Moving overset grid is employed to account for contrary rotations of two rotors. The validity of the method is verified by comparing with the experimental data. The aerodynamic performance and flow field characteristics of a coaxial rigid rotor in hovering condition are analyzed. Results indicate that the aerodynamic interaction can be divided into four aspects. The vortex induced effect is produced by the wake vortex of the coaxial rotor,which makes the aerodynamic performance of the upper rotor superior to the lower one. Periodic meeting of the double rotor leads to the blade loading effect,which produces periodic thrust fluctuations of the upper and lower rotors. The thickness effect makes opposite pulse fluctuations of the upper and lower rotor at meeting azimuths. The vertical blade - vortex interaction effect is caused by the collision between blade tip vortex from the upper rotor and the lower rotor blade,which affects the spanwise thrust distribution of the blade.
A numerical method based on Navier-Stokes(N-S) equations is developed to simulate the aerodynamic interaction of rigid coaxial rotor. Moving overset grid is employed to account for contrary rotations of two rotors. The validity of the method is verified by comparing with the experimental data. The aerodynamic performance and flow field characteristics of a coaxial rigid rotor in hovering condition are analyzed. Results indicate that the aerodynamic interaction can be divided into four aspects. The vortex induced effect is produced by the wake vortex of the coaxial rotor,which makes the aerodynamic performance of the upper rotor superior to the lower one. Periodic meeting of the double rotor leads to the blade loading effect,which produces periodic thrust fluctuations of the upper and lower rotors. The thickness effect makes opposite pulse fluctuations of the upper and lower rotor at meeting azimuths. The vertical blade - vortex interaction effect is caused by the collision between blade tip vortex from the upper rotor and the lower rotor blade,which affects the spanwise thrust distribution of the blade.
引文
[1]LEISHMAN J G,ANANTHAN S.Aerodynamic optimization of a coaxial proprotor[C]//Proceeding of the 62nd Annual Forum of the American Helicopter Society.Arizona:American Helicopter Society,2006:64-85.
[2]LEISHMAN J G,ANANTHAN S.An optimum coaxial rotor system for axial flight[J].Journal of the American Helicopter Society,2008,53(4):366-381.
[3]COLEMAN C P.A survey of theoretical and experimental coaxial rotor aerodynamic research[R].NASA TP-3675 Technical Paper,1997.
[4]LEISHMAN J G,BHAGWAT M J,BAGAI A.Free-vortex filament methods for the analysis of helicopter rotor wakes[J].Journal of Aircraft,2002,39(5):759-775.
[5]GRIFFITHS D A,LEISHMAN J G.A study of dual-rotor interference and ground effect using a free-vortex wake model[C]//Proceedings of the 58th Annual Fo-rum and Technology Display of the American Helicopter Society International.[S.l.]:AHS,2002.
[6]黄水林,徐国华,李春华.基于自由尾迹方法的共轴式双旋翼流场分析[J].南京航空航天大学学报,2008,40(6):721-726.HUANG Shuilin,XU Guohua,LI Chunhua.Flow field analysis of coaxial twin rotors based on free wake[J].Journal of Nanjing University of Aeronautics&Astronautics,2008,40(6):721-726.
[7]童自力,孙茂.共轴双旋翼气动力特性的计算研究[J].航空学报,1999,20(4):348-350.TONG Zili,SUN Mao.Navier-Stokes analysis of the aerodynamic properties of coaxial rotors[J].Acta Ae-ronautica et Astronautica Sinica,1999,20(4):348-350.
[8]许和勇,叶正寅.悬停共轴双旋翼干扰流动数值模拟[J].航空动力学报,2011,26(2):453-457.XU Heyong,YE Zhengyin.Numerical simulation of interaction unsteady flows around coaxial rotors in hover[J].Journal of Aerospace Power,2011,26(2):453-457.
[9]叶靓,徐国华.共轴式双旋翼悬停流场和气动力的CFD计算[J].空气动力学学报,2012,30(4):437-442.YE Liang,XU Guohua.Calculation on flow field and aerodynamic force of coaxial rotors in hover with CFDmethod[J].Acta Aerondynamica Sinica,2012,30(4):437-442.
[10]LAKSHMINARAYAN V K,BADER J D.Computational investigation of small scale coaxial rotor aerodynamics in hover[R].AIAA 2009-1069,2009.
[11]朱正,招启军,李鹏.悬停状态共轴刚性双旋翼非定常流动干扰机理[J].航空学报,2016,37(2):568-578.ZHU Zheng,ZHAO Qijun,LI Peng.Unsteady flow interaction mechanism of coaxial rigid rotors in hover[J].Acta Aeronautica et Astronautica Sinica,2016,37(2):568-578.
[12]HARRINGTON R D.Full-scale-tunnel investigation of the static-thrust performance of a coaxial helicopter rotor[R].NACA TN-2318,1951.
[13]马杨超,于世美,邓彦敏.共轴式双旋翼悬停诱导速度场的PIV实验研究[J].实验流体力学,2012,26(1):16-20.MA Yangchao,YU Shimei,DENG Yanmin.PIVexperimental investigation of coaxial rotors’induced velocity field in hover[J].Journal of Experiments in Fluid Mechanics,2012,26(1):16-20.
[14]雷瑶,纪玉霞,汪长炜.微型共轴双旋翼气动性能数值模拟与试验分析[J].实验流体力学,2017,31(5):67-73.LEI Yao,JI Yuxia,WANG Changwei.Numerical simulation and experimental study on aerodynamics of the micro coaxial rotors[J].Journal of Experiments in Fluid Mechanics,2017,31(5):67-73.
[15]樊枫,徐国华,史勇杰.基于N-S方程的剪刀式尾桨前飞状态气动力计算研究[J].空气动力学学报,2014,32(4):527-533.FAN Feng,XU Guohua,SHI Yongjie.Computation research on aerodynamic forces of scissors tail-rotor in forward flight based on the N-S equations[J].Acta Aerondynamica Sinica,2014,32(4):527-533.
[16]ROE P L.Approximate riemann solvers,parameter vectors,and difference schemes[J].Journal of Com-putational Physics,1981,43(2):357-372.
[17]LUO H,BAUM J D.A fast,matrix-free implicit method for computing low mach number flows on unstructured grids[R].AIAA 99-3315,1999.
[18]SPALART P R,ALLMARAS S R.A one-equation turbulence model for aerodynamic flows[R].AIAA92-0439,1992.
[2]LEISHMAN J G,ANANTHAN S.An optimum coaxial rotor system for axial flight[J].Journal of the American Helicopter Society,2008,53(4):366-381.
[3]COLEMAN C P.A survey of theoretical and experimental coaxial rotor aerodynamic research[R].NASA TP-3675 Technical Paper,1997.
[4]LEISHMAN J G,BHAGWAT M J,BAGAI A.Free-vortex filament methods for the analysis of helicopter rotor wakes[J].Journal of Aircraft,2002,39(5):759-775.
[5]GRIFFITHS D A,LEISHMAN J G.A study of dual-rotor interference and ground effect using a free-vortex wake model[C]//Proceedings of the 58th Annual Fo-rum and Technology Display of the American Helicopter Society International.[S.l.]:AHS,2002.
[6]黄水林,徐国华,李春华.基于自由尾迹方法的共轴式双旋翼流场分析[J].南京航空航天大学学报,2008,40(6):721-726.HUANG Shuilin,XU Guohua,LI Chunhua.Flow field analysis of coaxial twin rotors based on free wake[J].Journal of Nanjing University of Aeronautics&Astronautics,2008,40(6):721-726.
[7]童自力,孙茂.共轴双旋翼气动力特性的计算研究[J].航空学报,1999,20(4):348-350.TONG Zili,SUN Mao.Navier-Stokes analysis of the aerodynamic properties of coaxial rotors[J].Acta Ae-ronautica et Astronautica Sinica,1999,20(4):348-350.
[8]许和勇,叶正寅.悬停共轴双旋翼干扰流动数值模拟[J].航空动力学报,2011,26(2):453-457.XU Heyong,YE Zhengyin.Numerical simulation of interaction unsteady flows around coaxial rotors in hover[J].Journal of Aerospace Power,2011,26(2):453-457.
[9]叶靓,徐国华.共轴式双旋翼悬停流场和气动力的CFD计算[J].空气动力学学报,2012,30(4):437-442.YE Liang,XU Guohua.Calculation on flow field and aerodynamic force of coaxial rotors in hover with CFDmethod[J].Acta Aerondynamica Sinica,2012,30(4):437-442.
[10]LAKSHMINARAYAN V K,BADER J D.Computational investigation of small scale coaxial rotor aerodynamics in hover[R].AIAA 2009-1069,2009.
[11]朱正,招启军,李鹏.悬停状态共轴刚性双旋翼非定常流动干扰机理[J].航空学报,2016,37(2):568-578.ZHU Zheng,ZHAO Qijun,LI Peng.Unsteady flow interaction mechanism of coaxial rigid rotors in hover[J].Acta Aeronautica et Astronautica Sinica,2016,37(2):568-578.
[12]HARRINGTON R D.Full-scale-tunnel investigation of the static-thrust performance of a coaxial helicopter rotor[R].NACA TN-2318,1951.
[13]马杨超,于世美,邓彦敏.共轴式双旋翼悬停诱导速度场的PIV实验研究[J].实验流体力学,2012,26(1):16-20.MA Yangchao,YU Shimei,DENG Yanmin.PIVexperimental investigation of coaxial rotors’induced velocity field in hover[J].Journal of Experiments in Fluid Mechanics,2012,26(1):16-20.
[14]雷瑶,纪玉霞,汪长炜.微型共轴双旋翼气动性能数值模拟与试验分析[J].实验流体力学,2017,31(5):67-73.LEI Yao,JI Yuxia,WANG Changwei.Numerical simulation and experimental study on aerodynamics of the micro coaxial rotors[J].Journal of Experiments in Fluid Mechanics,2017,31(5):67-73.
[15]樊枫,徐国华,史勇杰.基于N-S方程的剪刀式尾桨前飞状态气动力计算研究[J].空气动力学学报,2014,32(4):527-533.FAN Feng,XU Guohua,SHI Yongjie.Computation research on aerodynamic forces of scissors tail-rotor in forward flight based on the N-S equations[J].Acta Aerondynamica Sinica,2014,32(4):527-533.
[16]ROE P L.Approximate riemann solvers,parameter vectors,and difference schemes[J].Journal of Com-putational Physics,1981,43(2):357-372.
[17]LUO H,BAUM J D.A fast,matrix-free implicit method for computing low mach number flows on unstructured grids[R].AIAA 99-3315,1999.
[18]SPALART P R,ALLMARAS S R.A one-equation turbulence model for aerodynamic flows[R].AIAA92-0439,1992.
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