涡破裂诱导的垂尾抖振数值模拟

Numerical Simulation of Vertical Tail Buffeting Induced by Vortex Breakdown

采用数值模拟方法研究了大后掠三角翼前缘涡破裂诱导的垂尾抖振问题,分析了大迎角条件下的垂尾抖振特性。采用Navier-Stokes方程求解非定常气动力、耦合结构动力学方程,建立了气动弹性方程,在时域内采用松耦合方式推进以得到垂尾结构响应。研究结果表明:涡破裂流的脉动频带覆盖了垂尾扭转模态的固有频率,诱发了垂尾抖振现象;与传统的颤振频域响应特性不同,垂尾抖振响应的各阶位移与加速度响应主频均位于各阶结构模态固有频率附近。此外,弯曲与扭转响应存在耦合效应,且耦合作用的频率与提取的垂尾表面气动载荷脉动频率一致。垂尾的位移响应由一阶弯曲模态主导,振幅不大;加速度响应主要由扭转模态产生,量级较大,使结构持续遭受严重的附加惯性载荷作用。

Numerical simulation of vertical tail buffeting under large angles of attack is accomplished using a delta wing/vertical tail configuration. The unsteady aerodynamic load upon the tail surface is calculated by employing a well-validated laminar Navier-Stokes equation solver. The structural dynamic equation is decoupled in the generalized coordinates and proceeds on the time-domain by four-stage Runge Kutta. The aeroelastic response of the flexible tail is predicted by coupling the two equations. The results show that the asymmetrical flow field formed by the interaction between the breakdown flow and the tail forces the structural deflection offsetting outboard. The bending and torsion responses of the tail structure are coupled and their frequency meets the pressure fluctuation upon the tail surface. Therefore, the interaction of bending and torsion responses governs the flow field surrounding the vertical tail. The slight amplitude vibrations are dominated by the first bending mode while accelerations with large quantitation are dominated by the torsion mode and subject the vertical tail to severe additional inertial load.