基于CFD方法的倾转旋翼机贴地飞行流场的数值分析

Focusing on the flowfield of a tiltrotor in ground effect (IGE), a computational fluid dynamics (CFD) method based on unstructured grid technique is established. In this method, the three-dimensional Euler equations have been taken as governing equations, the discretization of convective fluxes and the time marching are completNumerical Simulation of the Flowfield of Tiltrotors in Ground Effect Based on CFD Methoded by Jameson scheme and five-step Runge-Kutta iteration respectively. The influence of the tiltrotor on its flowfield is modeled as a distribution of momentum source. The ground is simulated as a wall boundary. The grids near the rotor planes and between the rotors and the ground is refined. Firstly, the method in this paper is validated by comparing the calculated results with the experimental results, which shows those match well. The V-22 tiltrotors are adopted to calculate the characteristics of flowfield at different altitude in hover and in low-speed forward flight in the IGE. In hover, because of the effect of ground on the downwash of rotors , the rotor wakes form spanwise flows along the ground which meet at the centerline of the two rotors and form a fountain flow in a similar fashion to what happens on the wing upper surface. The flowfield is simulated at different forward speed, at the same time the influence of velocity on the characteristics of flowfield has been analyzed.