Performance Predictions of Multirotor Vehicles Using A Higher-Order Potential Flow Method

摘要

A higher-order potential flow method is modified for aerodynamic performance predictions of small rotors. The rotor blades and their wakes are discretized using so-called distributed vorticity elements. Subsequently, the wake is represented by a continues vortex sheet, which is developed using a time-stepping procedure as either a fixed or relaxed wake. Viscous effects are captured using a strip method and an analytical high angle of attack stall model is applied. The aerodynamic load predictions of the higher-order potential flow method compare well with results from wind-tunnel experiments over a wide range of inflow conditions. In comparison to results based on blade element momentum theory, it also provides improved thrust and power predictions for descending flight and high advance ratios. The predicted radial loading during hover agree well with experimental observations. The rotor model is integrated into a two typical quadrotor configuration, with one leading rotor, or diamond configuration, and with two leading rotors, or square configuration, in order to explore effects specific to these configurations. A finding for the diamond configurations it that direction rotation of the leading rotor impacts the thrust and rolling moment of the mid-rotors. One finding for square configurations is that having the retreating blades of the lead rotors move along the vehicle centerline rather than the other way around results in slightly higher total thrust and tendency to pitch up. These tendencies increase with increasing edgewise flight and advance ratios.