Parallel Computation of Turbulent Combustion Processes on Individually Discretized Domains

The aim of this work is the parallel solution of large 3D-CFD problems concerning the numerical description of turbulent combustion and pollutant formation processes in coal-fired utility boilers. The in-house developed multi-domain CFD code AIOLOS for quasi-stationary, weakly compressible, turbulent reacting flows is used. The code is based on a conservative finite-volume formulation with a collocated grid. Submodels for fluid flow, turbulence, combustion and radiative heat transfer are included. In order to achieve a high flexibility in the discretization of the physical space a domain decomposition technique is applied. It allows the completely individual design of the different domains concerning the choice of the applied physical models, numerical methods and grid resolution. Using the domain decomposition technique for parallelization would lead to a loss in flexibility since the domains must be discretized with regard to load balancing aspects in order to obtain an acceptable speed-up. Parallel execution is therefore performed by DO-loop parallelization using data-parallel programming languages like High Performance Fortran (HPF). Thus remarkable speed-up is obtained without sacrificing the high flexibility in the discretization of the physical space. The parallel performance is demonstrated for the numerical simulation of two industrial scale utility boilers with an electrical output of 600 MW and 750 MW, respectively. Performance results are given for a Cray C90 (4 CPUs / shared memory), Cray J90 (16 CPUs / shared memory) and a Cray T3D (32 CPUs / virtual shared memory).