| A multigrid algorithm to accelerate the convergence of the computation of compressible aerodynamic flows on multi-block grids is presented. The diagonal form of an approximately-factored time-marching method is employed in each block to advance the solution to steady state. Block interfaces are treated by overlapping the blocks by one column of points and using halo points. In the multigrid cycle, there is communication between blocks at all levels. Turbulent viscosity is calculated using the Spalart-Allmaras turbulence model. A wide variety of tests are studied, including viscid flows around single airfoils for C-mesh and H-mesh topologies. Two multi-element test cases are investigated, the NLR-7301 airfoil and flap, and case A-2 from the AGARD Advisory Report No. 303. Good performance is shown in all test cases. Compared to the single-grid solver, multigrid converges to steady state in one-third to one-sixth the time. |
