共轴刚性旋翼悬停状态气动干扰机理

Research on Aerodynamic Interaction Mechanism of Rigid Coaxial Rotor in Hover

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.