Coupled Viscous Vortex Particle Method and Unstructured Computational Fluid Dynamics Solver for Rotorcraft Aerodynamic Interaction Analysis

This paper presents a hybrid fluid solver which couples a grid-free viscous vortex particle method with gridbased unstructured Computational Fluid Dynamics (CFD) solvers. The solver was developed to address the challenging rotor wake and aerodynamic interaction problem. The viscous vortex particle model is a state-of-the-art rotor wake modeling technology that can accurately solve for the complicated rotor wake variation while the unstructured Computational Fluid Dynamics (CFD) solvers can accurately predict the near-body flow. In this coupled solution, the vortex particle method is used to transport vorticity over the flow field while the Computational Fluid Dynamics (CFD) solvers are used to solve near-body flow and provide vorticity sources to the vortex particle method. The wake effect is fed back to the CFD solution to form a coupled solution. This paper discusses the fundamental aspects of the methodology and the associated algorithms that were used to couple the viscous vortex particle method and the unstructured CFD solvers. The developed hybrid tool was used to investigate the unsteady aerodynamic interactions between the helicopter rotor and body and excellent correlations between the simulation results and the measurements were achieved.