Non-inertial multiblock Navier-Stokes calculation for hovering rotor flowfields using relative velocity approach

A three dimensional Navier-Stokes solver is presented for calculating the h overing rotor flowfield using Osher's approximate Riemann solver. The Navie r-Stokes equations are recast in the attached blade relative system using r elative flow velocities as variables. Multiblock techniques are used to obt ain a structured grid around the blade. A modified MUSCL scheme is proposed to alleviate the inaccuracy in the discretisation of the relative variable formulation. The calculations are performed for a two-bladed model rotor o n C-H, O-O and C-H cylindrical grid topologies respectively. Computational solutions show reasonably good agreement with the experimental data for dif ferent lifting cases. The difficulty and suitability of different grid topo logies for capturing the lip vortex is illustrated. The differences between Euler and Navier-Stokes solutions and between wake modelling and wake capt uring approaches are also revealed. The results indicate that the relative velocity approach can give reasonable results for hovering rotor flowfields if due care is taken in minimising possible numerical errors.