The effect of multigrid acceleration implemented within an upwind-biased Eu
ler method for hovering rotor flows is presented. The requirement to captur
e the vortical wake development over several turns means a long numerical i
ntegration time is required for hovering rotors, and the solution (wake) aw
ay from the blade is significant. Furthermore, the flow in the region near
the blade root is effectively incompressible. Hence, the solution evolution
and convergence is different to a fixed wing case where convergence depend
s primarily on propagating errors away from the surface as quickly as possi
ble, and multigrid acceleration is shown to be less effective for hovering
rotor flows. It is found that a simple V-cycle is the most effective, smoot
hing in the decreasing mesh density direction only, with a relaxed trilinea
r prolongation operator. Results are presented for multigrid computations w
ith 2, 3, 4, and 5 mesh levels, and a CPU reduction of approximately 80% is
demonstrated for five mesh levels.