Parametric Validation Study for a Hovering Rotor using UT-GENCAS

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 order to bring the simulation to a more practical state for industry, a modified hybrid Navier-Stokes/Free-wake method has been introduced, which successfully reduced grid count and simulation time by one order of magnitude compared to full Navier-Stokes simulations. 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. The impacts of tip design and tip-speed variations were captured well. Furthermore, solution sensitivity to grid density, sub-iteration convergence, and turbulence model were investigated. The physical mechanisms of tip-design impact on hover performance were also studied.