Nonlinear Unsteady Vortex-Lattice Vortex-Particle Method with Adaptive Wake Conversion for Rotorcraft Aerodynamics

Abstract

Nonlinear unsteady vortex lattice-vortex particle methods (NL-UVLM-VPM) provide medium-fidelity predictions of rotorcraft aerodynamics with explicit three-dimensional wake representations at a moderate computational cost. This study presents an NL-UVLM-VPM approach with a scale-consistent adaptive wake panel-particle conversion strategy that mitigates the inherent temporal-spatial resolution coupling of conventional wake treatments in rotorcraft aerodynamic simulations. Numerical assessment shows that this strategy preserves the near third-order temporal convergence of the underlying time-integration scheme while improving robustness under coarsened temporal resolution. For a representative hover case, computational time is reduced by 29% relative to the conventional conversion strategy at identical temporal resolution and by nearly 70% compared with a fine-resolution reference simulation over 20 rotor revolutions, while maintaining thrust and torque predictions within 1% of the reference solution. Based on these analyzes, practical recommendations for particle conversion parameters and wake resolution are provided. The methodology is further validated for increasingly complex scenarios, including hover, forward flight with blade-vortex interaction, and multirotor interaction. Predictions show good agreement with experimental data and dedicated unsteady Reynolds-averaged Navier-Stokes simulations (URANS), while computational speedups exceeding two orders of magnitude relative to URANS are achieved.