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在现代飞行器设计中,数值模拟方法以低成本、高效率和高灵活性等优点成为研究飞行器空气动力学的重要方法。在旋翼型无人机流场模拟中,由于旋翼与机身存在相互作用,为获得精确模拟结果需要对整个无人机的流场进行模拟,因此,有效地模拟旋翼与机身的相对运动是实现成功模拟的关键步骤,这使得此类模拟问题极具挑战性。文章设计了一套求解旋翼型无人机空气动力学数值模拟问题的基于非结构滑移网格技术的高可扩展并行计算方法。该方法对控制方程的离散,在空间方向采用非结构移动网格有限元方法,时间推进采用全隐式二阶向后差分格式,最后采用一种并行Newton-Krylov-Schwarz方法求解离散后的非线性方程组。作为应用,文章对一个真实旋翼型无人机模型在悬停状态下的外流场进行了数值模拟,获得了一些非常详细的流场信息。数值结果显示,算法在天河2号上使用4 096个处理器核时仍具有接近线性的并行加速比,这为下一步开展旋翼型无人机的高保真度快速模拟奠定了良好的基础。
In modern aircraft design, the numerical simulation method is an important method to study aircraft aerodynamics with the advantages of low cost, high efficiency and high flexibility. Due to the interaction between the rotor and the fuselage, in order to obtain accurate simulation results, it is necessary to simulate the flow field of the entire UAV. Therefore, the relative motion between the rotor and the fuselage is effectively simulated Achieving the key steps in successful simulation makes this type of simulation challenging. In this paper, a highly scalable parallel computing method based on unstructured slipping grid technique is designed to solve aerodynamic numerical simulation of rotorcraft. This method uses the non-structural finite element method of moving mesh in the spatial direction and the fully implicit second-order backward difference scheme in time. Finally, a parallel Newton-Krylov-Schwarz method is used to solve the discrete Linear equations. As an application, the numerical simulation of the outflow field in a hovering state of a true rotary-wing UAV model is given, and some very detailed flow field information is obtained. The numerical results show that the algorithm still has a parallel linear speedup when using 4 096 processor cores on Tianhe No.2, which lays a good foundation for the next high speed fidelity simulation of a rotary UAV.