Algebraic multigrid preconditioned Krylov subspace methods for fluid flow and heat transfer on unstructured meshes

A numerical tool, Thermoflow, is developed for simulating the three-dimensional incompressible viscous flow and heat transfer on unstructured meshes. It is based on a cell-centered, collocated finite-volume method. The velocity-pressure coupling is treated using the SIMPLE/C algorithm. An agglomerated multigrid method (AgMG) and the AgMG preconditioned Krylov subspace methods are implemented to solve the linearized partial differential equations. Their performances are evaluated against the public code, AMG1R5. It has been found that all hybrid solvers are superior to the standalone AgMG when a stringent convergence criterion is imposed, but the superiority is weakened with the convergence criterion coarsening. Due to its expensive setup cost, A MG1R5 is not appropriate for the segregated solver.