非定常预处理方法在倾转旋翼飞行器悬停状态气动干扰模拟中的应用

针对倾转旋翼飞行器的多种速度尺度并存的复杂流动问题，发展了能够统一求解同时包含不可压缩流动和可压缩流动的非定常预处理方法和一种考虑了流场物理信息传播方向的预处理远场边界条件。结合适用于倾转旋翼飞行器的复杂外形及大位移问题的非结构混合网格技术和重叠插值技术，建立了倾转旋翼飞行器的数值模拟方法。在此基础上，首先通过悬停算例验证了数值方法的有效性，确定了选择预处理截断参数的原则。然后探究了倾转旋翼飞行器直升机模式悬停状态的尾迹涡结构演化过程，研究了“喷泉效应”和“地面效应”对倾转旋翼气动性能的影响。计算结果表明，旋翼尾迹涡的耗散在不同方位角存在较大差异。“地面效应”抑制了旋翼尾迹的发展，提高了旋翼整个方位角区域的升力系数，而不仅限于机翼上方方位角区域。 “地面效应”作用强于“喷泉效应”作用，使旋翼相对于孤立旋翼拉力系数略微增大了5.26%，但同时整个倾转旋翼飞行器的总的向上的力只有孤立旋翼拉力的82.46%。结论表明预处理方法和预处理远场边界条件能够较好地模拟倾转旋翼飞行器悬停状态的干扰流场，兼顾了数值计算的耗散性和稳定性。气动干扰对倾转旋翼飞行器整体气动性能有重大影响。 

Application of unsteady preconditioning to aerodynamic interaction simulation of tiltrotor aircraft in hover

To solve the tiltrotor aircrafts complicated flow problems of different speed scales, an unsteady pre-conditioning method and corresponding boundary conditions were developed for simultaneous solution of incompressible and compressible flows. Combined with the unstructured hybrid grid generation technique and the overlapping grid interpolation technique suitable for the complex configuration and large displacement of tiltrotor aircraft, a numerical simulation method for tiltrotor aircraft was presented. On this basis, the validity of the numerical method was verified by hovering case at first, and the principle of preconditioning parameter selection was determined. Then, the wake vortex structure evolution of the hovering configuration for the helicopter mode was investigated, and the effects of “fountain effect” and “ground effect” on the aerodynamic performance of tiltrotor were studied. The results showed that the dissipation of the wake vortex presented different scene in different azimuthal zones. And “ground effect”, coupled with “fountain effect”, suppressed the development of rotor wake. The “ground effect” affected the entire azimuthal zone instead of the zone above the wing, causing a slight increase of 5.26% in the thrust coefficient of the installed rotor relative to the isolated rotor, but the total thrust coefficient of the whole tiltrotor aircraft were only 82.46% of the isolated rotor. The conclusion shows that the preconditioning method is able to simulate the complicated flow field in the hovering configuration of the helicopter model well. Aerodynamic interaction has a significant impact on the overall aerodynamic performance of the tiltrotor aircraft.