Analysis of a Hovering Rotor using UT-GENCAS: A Modified Hybrid Navier-Stokes/Free-Wake Method

摘要

Analysis of rotors in hover has always been a significant challenge. The presence of strong vortices underneath the rotor requires a large amount of grid points to properly capture the vorticity and many time steps are required to reach a time-independent state. In this study, a hybrid Navier-Stokes/free-wake method is used to preserve trailing vortices with a lower grid count. In order to achieve fast steady performance solution, two wake modeling approaches are introduced. One is a free-wake model with relaxation, and the other is a constrained down-wash wake model based on Landgrebe model. In this hybrid method, Navier-Stokes and free-wake solvers are loosely coupled for fast convergence in hover. The S-76 model-scale blades with three tip designs were studied to assess current approaches. The proposed approaches showed reasonable to good correlation with measured Figure of Merit, thrust and torque data, and the impacts of tip design and tip speed variations were captured well.