Accelerating the Convergence of Multiphase Flow Simulations ‎when Employing Non-Uniform Structured Grids

Non-uniform grids inevitably arise in multiphase flow simulation scenarios due to the need to resolve near-wall phenomena and/or large L/D ratios associated with the reactor configuration. This in conjunction with large density ratios of the constituent phases can retard the convergence of the pressurecorrection equation that results from applying operatorsplitting methods to the incompressible NavierStokes equations. Various preconditioning strategies to this illconditioned pressurecorrection matrix are explored in this study for a class of bubbling bed simulations encompassing: different particle densities, bedheights and dimensions (2D/3D). The rightside Block Jacobi preconditioning option resulted in a 20 - 35% decrease in CPU time that correlated well with a decrease in the number of iterations to reach a specified tolerance.