Abstract
Porting of the legacy code MFIX to a high performance computer (HPC) and the use
of high resolution simulations for the design of a coal gasifier are described here. MFIX is
based on a continuum multiphase flow model that considers gas and solids to form
interpenetrating continua. Low resolution simulations of a commercial scale gasifier with a
validated MFIX model revealed interesting physical phenomena with implications on the
gasifier design, which prompted the study reported here. To be predictive, the simulations need
to model the spatiotemporal variations in gas and solids volume fractions, velocities,
temperatures with any associated phase change and chemical reactions. These processes occur
at various time- and length-scales requiring very high spatial resolution and large number of
iterations with small time-steps. We were able to perform perhaps the largest known
simulations of gas-solids reacting flows, providing detailed information about the gas-solids
flow structure and the pressure, temperature and species distribution in the gasifier. One key
finding is the new features of the coal jet trajectory revealed with the high spatial resolution,
which provides information on the accuracy of the lower resolution simulations.
Methodologies for effectively combining high and low resolution simulations for design
studies must be developed. From a computational science perspective, we found that global
communication has to be reduced to achieve scalability to 1000s of cores, hybrid
parallelization is required to effectively utilize the multicore chips, and the wait time in the
batch queue significantly increases the actual time-to-solution. From our experience,
development is required in the following areas: efficient solvers for heterogeneous, massively
parallel systems; data analysis tools to extract information from large data sets; and
programming environments for easily porting legacy codes to HPC.