Aerodynamic characteristics of tilt-rotor UAVs are usually simulated by computational fluid dynamics (CFD) only, and the fuselage/wing is fixed in simulations. It is difficult for this method to consider drastic changes of the aerodynamic forces and flowfield originating from conversion of flight modes. And during flight-mode conversions, the rapid changes of postures of tilt-rotors will unavoidably bring great influence on aerodynamic characteristics. In addition, the simulation of the control system for flight-mode conversions cannot be realised by CFD only. In this paper, considering the motion of the fuselage/wing and the dynamic tilting process of tilt-rotors, a new computational method by coupling CFD and multi-body dynamics (MBD) is presented for flight-mode conversions of a tilt tri-rotor UAV with the large-space computational domain. The numerical results validate the feasibility of the coupling method and also show effects of the fuselage/wing motion and flight-mode conversions to aerodynamic characteristics of the tilt tri-rotor UAV.

中文翻译：

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倾转三旋翼无人机飞行模式转换的CFD/MBD耦合方法

倾转旋翼无人机的气动特性通常仅通过计算流体动力学（CFD）进行模拟，机身/机翼在模拟中是固定的。该方法难以考虑由飞行模式转换引起的气动力和流场的剧烈变化。而在飞行模式转换过程中，倾转旋翼姿态的快速变化不可避免地会对气动特性产生很大的影响。此外，飞行模式转换控制系统的仿真不能仅通过CFD来实现。在本文中，考虑机身/机翼的运动和倾转旋翼的动态倾斜过程，提出了一种结合 CFD 和多体动力学 (MBD) 的新的计算方法，用于倾转三旋翼的飞行模式转换。具有大空间计算域的无人机。