Efficient Numerical Techniques for Simulating a Rotorcraft Flow Field with Overlapping Grids

We propose efficient and accurate techniques for simulating a time-periodic, unsteady rotorcraft flow. The Reynolds-averaged Navier–Stokes equations are solved on overlapping grids using a multigrid method and time spectral method. A new implementation of the multigrid algorithm for overlapping grids is proposed to accelerate hovering and forward-flight computations. Using the time-lagged periodic boundary condition, the time spectral method is combined with the multigrid scheme to significantly improve the simulation efficiency of a helicopter rotor in forward flight. The resulting equations are solved by the implicit lower-upper symmetric-Gauss–Seidel scheme. Some hovering and forward-flight cases are simulated, and the results are compared with experimental data, demonstrating the high efficiency and accuracy of the proposed method.