飞翼无人机低速着陆状态抖振响应研究

基于RANS方程和SST湍流模型,采用飞翼无人机升力系数判据、俯仰力矩判据和表面极限流判据等对抖振始发迎角度进行了预测估计。基于较为详细的结构模型和气动模型,构造了结构与气动的耦合求解技术,同时采用弹簧近似光滑和局部重构组合方法对气动的动网格技术进行更新;然后分别在时频域内分析了飞翼无人机的抖振载荷响应。研究结果表明:基于CFD的RANS方程、SST湍流模型及各类判据预计刚性飞翼无人机在低速大迎角状态下的抖振始发迎角可以得到较为合理的结果;采用升力系数判据、俯仰力矩系数判据预测的抖振始发迎角与表面极限流判据预测的始发迎角相比要保守一些;而表面极限流判据方法能给出翼面气流流动的细节,采用此判据可以分析对比不同迎角下的翼面气流流动变化情况;与气动弹性及嗡鸣响应相比,抖振是一种强迫振动,其响应频率并不单一。

Buffeting Response of Flying-Wing UAV in Low-Speed Landing Condition

The buffeting onset angle is estimated based on the Reynolds averaged Navier-Stokes(RANS) equation and the shear stress transport (SST) turbulence model, which is according to the lift coefficient criterion, pitching moment criterion and surface limit flow criterion of flying-wing unmanned aerialvehicle (UAV). Based on the detailed structure model and aerodynamic model, the structural aerodynamic coupling solving technology is built. The aerodynamic dynamic meshes adopt the combination of the spring-based and local remeshing methods. The buffeting load responses of flying-wing UAV are calculated in the time and frequency domains, respectively. The results show that based on the CFD RANS equations, the SST turbulence model and different kinds of criterions, the rigid flying-wing UAV in low-speed high-angle condition can get reasonable buffeting onset angles. The angles predicted by the lift coefficient criterion and the pitching moment coefficient criterion are more conservative than ones predicted by the surface limit flow criterion; the surface limit flow criterion method can give the detailed wing flow and the wing flow characteristics at different angles. Compared with other aeroelastic responses, buffeting is the forced vibrations, and the response frequency is not single.