Free-wake Analysis of Hovering Rotor in Ground Effect

A free-wake based model with fine convergence is developed to predict the wake geometry of a hovering rotor operating in ground effect(IGE).The vortex line is discretized into straight-line filaments,and the influence of the ground is modeled using a surface panel method.Since earlier studies show it is hard for the free-wake to converge when the rotor is hovering at a low height,the work of this study incorporates several modification measures to improve the convergence of the model,such as rectifying the wake vortices below the ground plane proportionally and distributing the ground panels circularly,which reduced the calculation amount of the model at the same time.The model is validated with prediction instances in which the rotor is placed at different heights.A comparison of the determined wake geometries with experimental data shows good agreement and proves the proposed model possesses good accuracy.