Parallel Computation for Radiative Heat Transfer Using the DOM in Combustion Applications: Direction, Frequency, Subdomain Decompositions, and Hybrid Methods

Abstract

In the framework of coupled large-eddy/discrete ordinates method (LES/DOM) computations of turbulent combustion problems, various decompositions for parallel calculations of the radiative heat transfer based on the DOM are investigated. The methods analyzed are: (A) a task decomposition on the discrete directions and frequencies with two numeric strategies: Message Passing Interface (MPI) with distributed memory and OpenMP with shared memory for the direction decomposition; (B) a new algorithm for a DOM subdomain decomposition, which is proposed and tested using MPI; and (C) hybrid methods combining an OpenMP strategy for direction and MPI for tasks and subdomain decomposition. It is shown for the case of coupled simulations that the convergence and the parallel efficiency of the domain decomposition (B) are optimal. This method is limited in this work to 25 sub-domains, at which point the efficiency stagnates. Combining the directions with frequency and/or domain decompositions in a hybrid method (C) results in very good efficiency up to 1,200 processors. This hybrid strategy is also very efficient in terms of memory usage. This work shows that the best way to perform massively parallel computation for radiative heat transfer with the DOM is to combine different decomposition levels. The analysis performed in this work shows the best parallel strategy to be used in coupled simulations between radiation and LES on massively parallel architectures.

Acknowledgments

The work was supported by the Fondation de Recherche en Aeronautique et Espace (FRAE) in the project STRASS: http://strass.cerfacs.fr, project coordinator E. Riber. We acknowledge Isabelle d'Ast from CERFACS for her help on the use of the cluster. Thanks to F. Andre from CETHIL for spectrum illustration.

Notes

¹PRISSMA: Parallel Radiation Solver with Spectral integration on Multicomponent mediA www.cerfacs.fr/prissma.

² www.cerfacs.fr/cfd/avbp.html.