Rotorcraft in-ground effect models in axial and forward flight

This paper presents in-ground effect (IGE) models that incorporate the rotor advance ratio and vehicle's climbing velocity to predict the IGE thrust variation in axial (vertical) and forward flight for rotor-based aerial vehicles, such as quadcopter uncrewed aerial vehicles (UAVs). Extensive experiments were conducted to validate each and every component of the new IGE models. Discrepancies between the analytical and experimental results in forward flight were found to be consistent with the two characteristic flow regimes of recirculation and ground vortex. Specifically, an additional increase in thrust was observed at a low advance ratio (μ<0.04) in the extreme ground-effect regime (z/R<0.5). The results of this study can be leveraged to develop new vehicle motion control and path planning algorithms for flying near obstacles.