Analyzing the Performance of a Hovering Ducted Rotor in Ground/Wall Effects to Improve the Controlling Aspects of VTOL Vehicles in Confined Spaces

This paper examines ground/wall effects on a ducted fan, with the aim to improve the handling quality of an unmanned aerial vehicle targeted for operations in confined spaces. In order to do this, flow field at different configurations of the fan-ground-wall is visualized computationally in Fluent. Herein the standard k-ε model and the non-equilibrium wall function are used to model the turbulence while the fan is modeled using the Virtual Blade Model (VBM). It is shown that in ground effects thrust is larger at distances relatively close to the ground. Adding a wall introduces an asymmetry to the flow which produces a considerable amount of horizontal force attracting the fan towards the wall. Moreover, in presence of the wall, the total thrust reduces slightly. The paper also describes the observation that at sufficiently close distances between the fan and the wall/ground, a large portion of the downwash re-enters to the fan which causes significant performance loss.