基于非结构重叠网格的螺旋桨滑流非定常数值模拟

基于各向异性非结构混合网格及多套网格重叠技术,通过求解非定常雷诺平均Navier-Stokes(URANS)方程,分别研究了螺旋桨动力特性和螺旋桨滑流对涡桨飞机气动特性影响。运用物面相交准则实现多套网格间的挖洞,采用距离权和三线性插值技术传递重叠区变量信息,并针对定轴旋转优化了网格重叠边界。采用双时间步求解控制方程,内迭代计算采用LU-SGS(lower-upper symmetric Gauss-Seidel)方法。模拟了单独螺旋桨旋转的非定常流动,计算的拉力系数和扭矩系数与试验结果一致,表明采用的数值方法和网格技术能有效模拟螺旋桨滑流效应。数值模拟了某涡桨飞机,对比了有无滑流下飞机的气动特性,给出了滑流对飞机影响。结果表明:滑流导致其后部气流加速和旋转,改变飞机气动特性,增大飞机的阻力和俯仰力矩,导致气流下洗,影响机翼及平尾压力分布。 

Unsteady numerical simulation of propeller slipstream based on unstructured chimera grid

Numerical simulations of unsteady Reynolds averaged Navier-Stokes (URANS) equations were conducted for isolated-propeller and turboprops configurations based on anisotropic unstructured chimera grids. Walls criterion was used in the automatic hole-cutting procedure. Distance weight interpolation and tri-linear interpolation were developed to transmit variable value. The computation grids contained rotational subzone of propeller and stationary subzone of aircraft. The boundaries of chimera grids were optimized for fixed axis rotation. The equations were solved by dual-time method and lower upper-symmetric Gauss-Seidel (LU-SGS). The method and grid technology were validated by isolated-propeller and the computation results were compared with experimental data, showing good agreement with each other. Then turboprops configuration was simulated and the aerodynamic characteristics of aircraft with or without slipstream were compared. The effect of slipstream was analyzed by surface pressure and pressure distribution of sections. The results indicated that the slipstream increased drag and pitching moment coefficient. Slipstream affected the pressure distributions of wing and flat-tail, causing the airflow downwash.