A Novel Viscous Vortex Particle Method as Applied to Unsteady Rotor Wake Modeling and Simulation

摘要

This paper summarizes the development and validation of a novel viscous vortex particle method (VVPM) as applied to the challenging unsteady rotor wake problem. The viscous vortex particle model developed is based on first principles and solves for the rotor wake vorticity convection and diffusion in the velocity-vorticity form of the incompressible Navier-Stokes equation. Compared to conventional rotor wake solutions, such as the free wake model, the VVPM can accurately address the rotor wake distortion, the tip vortex roll-up, and the vorticity diffusion from the first principle solution without relying on any empirical estimation of the modeling parameters as is required for existing free wake codes. The current grid based Navier-Stokes CFD methods also encounter the serious hurdle of artificial numerical dissipation due to the numerical discretization and, hence, cannot accurately capture the rotor wake vorticity variation for accurate rotor performance prediction or for any meaningful analysis of aerodynamic interactional problems. The VVPM developed through this research adopts a grid-free Lagrangian simulation where there is no artificial numerical dissipation involved. This paper discusses the theoretical viscous vortex particle formulation and the corresponding numerical technique for the rotor wake solution. The simulation results obtained agreed well with measured data, which validates the new viscous vortex particle method.