基于后缘小翼的旋翼翼型动态失速控制分析

针对后缘小翼(TEF)的典型运动参数对旋翼翼型动态失速特性的控制进行了研究。发展了一套适用于带有后缘小翼控制的旋翼翼型非定常流动特性模拟的高效、高精度CFD方法。通过求解Poisson方程生成围绕旋翼翼型的黏性贴体和正交网格,为保证后缘小翼附近的网格生成质量,建立了基于翼型点重构的方法来描述后缘小翼的偏转运动;为克服变形网格方法可能导致网格畸变的不足,发展了一套适用于带有后缘小翼控制的旋翼翼型运动嵌套网格方法。基于非定常雷诺平均Navier-Stokes(URANS)方程、双时间法、Spalart-Allmaras(S-A)湍流模型和Roe-Monotone Upwind-centered Scheme for Conservation Laws(Roe-MUSCL)插值格式,发展了旋翼翼型非定常气动特性分析的高精度数值方法,并采用Lower-Upper Symmetric Gauss-Seidel(LU-SGS)隐式时间推进方法及并行技术提高计算效率。以有试验结果验证的HH-02翼型和SC1095翼型为算例,精确捕捉了动态失速状态下的气动力迟滞效应,验证了本文方法的有效性。着重针对SC1095旋翼翼型的动态失速状态开展后缘小翼的控制分析,提出了可以体现翼型升力、阻力及力矩综合特性的关系式Po和Pc,揭示了后缘小翼振荡频率、相位差和偏转幅值对动态失速特性影响的规律。研究结果表明:当后缘小翼偏转的相对运动频率为1.0,且小翼运动规律与翼型振荡规律之间的相位差为0°时,后缘小翼能够更好地抑制翼型动态失速现象;在此状态下,当偏转幅值为10°时,SC1095翼型最大阻力系数和最大力矩系数可以分别降低19%和27%。

Dynamic stall control of rotor airfoil via trailing-edge flap

Control effects of typical motion parameters of trailing-edge flap (TEF) on the dynamic stall characteristics of rotor airfoil are investigated.A high-efficiency and high-precision CFD method for predicting the unsteady flow characteristics of rotor airfoil with TEF control is developed.The viscous and orthogonal body-fitted grids around the oscillatory rotor airfoil are regenerated by solving Poisson equations.To ensure the quality of the grids around TEF,a reconstruction of grid points on airfoil is conducted to describe the motion of TEF.Aiming at overcoming the shortcoming of deformable grid approach,which may result in the distortion of grid,a moving-embedded grid method is developed to predict the flowfield of the oscillatory airfoil with TEF control.Based on unsteady Reynolds averaged Navier-Stokes (URANS) equations,dual-time method,Spalart-Allmaras (S-A) turbulence model,and Roe-Monotone Upwind-centered Scheme for Conservation Laws (RoeMUSCL) scheme,a high-precision CFD method for predicting the flowfield around airfoil is developed,and implicit LowerUpper Symmetric Gauss-Seidel (LU-SGS) scheme and parallel techniques are adopted to improve computational efficiency.The dynamic stall cases of HH-02 and SC1095 rotor airfoils are calculated using the proposed method.It is demonstrated that the hysteresis effects are well captured,verifying the effectiveness of numerical simulation method.Focusing on the dynamic stall cases of SC1095 rotor airfoil,analyses on dynamic stall control via TEF are carried out.The function Pc and Pc which can reflect the lift,drag and moment characteristics of airfoil are proposed.The effects of the non-dimensional frequency,the phase difference and the angular amplitude of the trailing-edge flap are revealed.The results indicate that dynamic stall phenomenon of an oscillatory airfoil could be significantly suppressed when relative motion frequency of the trailing-edge flap is 1.0 and the phase difference is about 0°.At this state,the maximum drag and negative moment coefficients of SC1095 airfoil can be reduced by about 19％ and 27％ respectively via TEF control when the angular amplitude is 10°.