Numerical simulation of rotor-wing transient interaction for a tiltrotor in the transition mode

Tiltrotor aerodynamic interaction, especially in the transition mode, is a necessary consideration for tiltrotor aerodynamics, and structural design and optimization. Previous studies have paid much attention to the helicopter mode. However, due to the substantial complexity of the problem, only a small amount of work on the transition mode has been done so far. In this paper, the rotor-wing aerodynamic interaction of a scaled V-22 Osprey tiltrotor, both in the helicopter and transition modes, are studied by computational fluid dynamics (CFD) numerical simulation. The flow field is discretized via the chimera mesh technique and then solved with the Reynolds-averaged Navier-Stokes (RANS) equations. The rotational acceleration of the rotor is considered as a source term added on the right side of the momentum equation of the RANS equations. Both a quasi-steady and a fully transient method are employed to simulate the tilt motion of the rotor in the transition mode. Both qualitative and quantitative results are presented and discussed on the aerodynamic forces, flow physics, and mechanisms. The applicability of the extensively used quasi-steady method for rotor tilt simulation is revealed.