Open Access

ARTICLE

An Evaluation of Multigrid Acceleration for the Simulation of an Edge FLame in a Mixing Layer

M. Wasserman^1,2, Y. Mor-Yossef^1,2, J.B. Greenberg¹

1 Faculty of Aerospace Engineering, Technion – Israel Institute of Technology., Haifa, Israel 32000.
2 Israeli CFD Center, Caesarea Industrial Park, Israel 38900.

Computer Modeling in Engineering & Sciences 2015, 106(3), 203-228. https://doi.org/10.3970/cmes.2015.106.203

Abstract

A test problem of a laminar edge flame formed in the mixing layer of two initially separated streams of fuel and oxidant is employed to evaluate the performance of multigrid acceleration of the iterative solution of the central difference finite difference scheme approximating the governing energy and species mass fraction conservation equations. The multigrid method was found to be extremely efficient and significantly improved the iterative convergence relative to that of a single grid method. For low to moderate chemical Damkohler numbers, acceleration factors of up to six (6!) times were recorded in the computational time required to obtain iterative convergence with the multigrid method, over that required with the single-grid method to obtain the same level of convergence. Moreover, monotonic convergence was obtained with the multigrid method in cases where the convergence of the single-grid method stalled. However, for large chemical Damkohler numbers of more than a thousand (i.e. very small characteristic chemical reaction times) and three levels of grid refinement the advantage of application of the multigrid method was seriously degraded due to the necessity to dampen errors stemming from the highly nonlinear chemical source terms on coarse grid levels of the multigrid hierarchy.

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Keywords

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