(184g) A Re-Indexing Method for Performance Improvement of Gas-Solids Flow Simulations

A Cartesian cut-cell method was recently implemented into the open-source multiphase flow solver MFIX (Multiphase Flow with Interphase Exchange). In the Eulerian/Eulerian approach, both gas and solids phases are treated as interpenetrating phases, and mass and momentum balance equation are solved for each phase. Momentum transfer between the solids and gas phase is achieved through an empirical drag law. MFIX employs a three-dimensional structured, staggered grid, which needs to be intersected with the geometry to identify fluid cells, boundary cells (called cut-cells), and blocked cells. During time advancement of the flow solution, a special treatment is required only for the cut-cells. For complex geometries, a large number of blocked cells can be generated, leading to a loss in performance. A new re-indexing method has been implemented to rearrange the data and loop only over active computational cells. The re-indexing method shows performance gain in the computations, in terms of memory management, and CPU time to solution. For parallel execution of the code, the data transfer is minimized and grid partition is optimized in terms of load imbalance. The re-indexing method is minimally invasive and timing results will be shown for gas-solids flow systems.