Aerodynamics and dynamics coupled modelling method for variable RPM multi-rotors

This article introduces a coupled aerodynamic and dynamic modelling method for variable RPM (VRPM) multi-rotor simulations, utilising an improved gimballed rotor dynamics model and the free vortex wake (FVW) method. Additional degrees of freedom in the gimballed rotor hub, as well as the shaft rotation and lead-lag motion, are modelled. The influence of VRPM on the rotor wake is incorporated into the FVW method. Thus, this simulation model allows the rotor to begin from a stationary state, accelerate to its operating RPM, and decelerate back to rest, covering a wide range of operating conditions relevant to VTOL vehicles. The simulation model is validated against wind tunnel test data, and multiple case studies are presented and analysed to showcase the VRPM multi-rotor simulation and the flight characteristics of the VRPM multi-rotors.