PRECONDITIONED MULTIGRID METHODS FOR 2-DIMENSIONAL COMBUSTION CALCULATIONS AT ALL SPEEDS

The development of an effective implicit integration strategy for two- dimensional (axisymmetric) combustion calculations at all speeds is pr esented. A time-derivative preconditioning technique is first combined with an implicit line relaxation algorithm to yield an approach capab le of removing the acoustic time step restriction at low flow speeds w hile handling stiff chemical kinetics in a fully implicit fashion, Num erical performance is further improved through the addition of a full multigrid/full approximation storage (FMG-FAS) convergence acceleratio n strategy. Numerical simulations of a subsonic reacting shear layer ( finite rate hydrogen-air chemistry), a subsonic bluff-body stabilized flame (mixing-limited methane-air chemistry), and a supersonic jet dif fusion flame (finite rate hydrogen-air chemistry) are presented to tes t the basic attributes of the algorithm, Comparisons with experimental data are presented for all cases, and a detailed examination of the c omputational efficiency of the new procedure is conducted, The strengt hs and weaknesses of multigrid ideas for fully coupled combustion calc ulations are particularly highlighted.