High-fidelity Simulation of the Volocopter-2X in Cruise Flight

Abstract

A comparison between high-fidelity simulations of a half and a full model approach of the Volocopter-2X (VC2X) in cruise flight is conducted. To ensure an identical flight condition for both cases a flight mechanics trim is performed. Therefore, the computational fluid dynamic (CFD) code FLOWer is loosely coupled to the flight mechanics tool VFAST. The half model simulation setup can save up to half of the cells and therefore also computational time. However, it is only valid for a center of gravity lying on the geometric symmetry plane and a coordinated flight with a zero sideslip angle and no roll rate. The comparison between the half and full model shows no visible difference in the mean rotor revolution speed and only small difference in the pitch attitude. The Volocopter flow is characterized by a high density of small-scale vortex structures. These result, on the one hand, from the rotor wake and rotor-rotor interactions and, on the other hand, from rotor-airframe interactions. A vortex tube developes near the symmetry plane above the rotor disc of the VC2X, which is more prominent in for the half model. The differences on the level of the individual rotors is for most rotors small, only the front outer rotors show bigger deviations.