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.

倾斜旋翼无人机的空气动力特性通常仅通过计算流体动力学（CFD）进行模拟，并且机身/机翼在模拟中是固定的。这种方法很难考虑源自飞行模式转换的空气动力和流场的急剧变化。在飞行模式转换期间，倾转旋翼姿态的快速变化将不可避免地对空气动力特性产生重大影响。此外，仅通过CFD不能实现用于飞行模式转换的控制系统的仿真。本文考虑了机身/机翼的运动以及俯仰旋翼的动态倾斜过程，提出了一种结合CFD和多体动力学（MBD）的新型计算方法，用于倾斜三旋翼的飞行模式转换。具有大空间计算域的无人机。