Prediction of the propeller / ground interaction of an unmanned aerial vehicle in hover flight with a Lattice Boltzmann flow solver

摘要

Micro air vehicle (MAVs) should be able to operate through highly confined environments, for example for civil rescue missions or archaeology investigations. In these confined environments, the distance between the propeller and the ground is reduced, resulting in a ground effect that largely affect the propeller performance [1]. Such ground effects are known to modify the lift, induce undesirable flow unsteadiness and can be responsible for maneuverability problems, for example in the case of a helicopter in hover flight above a sandy landing area. The main difficulties to accurately predict the interaction between the propeller and the ground are related to the rotating movement of the blade, 3D flow effects and turbulence. Moreover, aerodynamic performance of conventional propellers drastically decreases in the case of MAVs due to the increased importance of flow viscous forces with respect to inertial forces. Basically, increased viscous effects tend to increase viscous drag and promote flow separation which leads to reduced efficiency and reduced maximum achievable lift respectively. Reduced efficiency and maximum achievable lift result in low endurance of MAVs (typically between 5 to 15 minutes for hovering capable micro-air vehicles) and limited payloads.