A numerical investigation of ground effect on rotorcraft in the presence of side wall

Abstract

Rotorcraft flying in close proximity to ground are known to generate a larger thrust due to the shed wake being obstructed by the ground. The effect has been well researched and empirical corrections are available in literature. However, studies on the influence of side walls on ground effect is still lacking. Such studies may be applied to full scale rotorcraft hovering near walls, skyscrapers and similar structures, rotor-based UAVs flying in a constrained space and in corrections for wall interference in wind tunnel testing. This work aims to study the influence of a side wall in the presence of ground effect on a lifting rotor using a CFD tool, RotCFD. Rotor thrust and torques were found to be largely unaffected by side wall interference. However, pitching and rolling moments of considerable magnitudes were observed. These appear to be a result of the asymmetry in the flowfield developed from wake recirculation and interference when the rotor is close to the wall and the ground.