Wake Turbulence Analysis of Rotor-Rotor Configuration in Forward Flight Under Varying Separation Distances

초록

Tip vortices generated at the blade tips induce wake turbulence, which can significantly degrade the flight stability of following rotorcraft. For conventional fixed-wing operations, separation standards based on maximum takeoff weight (MTOW) have been established to mitigate wake interference. However, these regulations are not directly applicable to Urban Air Mobility (UAM) vehicles, which generally feature lower takeoff weights and higher disk loading. In particular, multi-rotor UAM platforms experience strong aerodynamic interactions among rotors, leading to increased wake instability and an accelerated transition to a turbulent wake state. It is essential to investigate wake characteristics specific to UAM configurations to develop appropriate separation criteria that ensure safe operations. As a preliminary study toward UAM wake analysis, this paper assesses how wake interference between two isolated rotors affects the aerodynamic performance of following rotor blades. Numerical simulations were conducted by coupling the Vortex Particle Method for capturing wake evolution, and the Nonlinear Vortex Lattice Method for predicting unsteady rotor aerodynamics with high computational efficiency. The effects of axial and lateral separation distances between two isolated rotors on variations in thrust, torque, and moments experienced by the following rotor due to wake interference.

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