Qualitative Benchmarking of a Developmental CFD-DEM Code*

\\MFiX-Exa is a new code being developed by the National Energy Technology Laboratory and Lawrence Berkeley National Laboratory as part of the U.S. Department of Energy's Exascale Computing Project. MFiX-Exa originated by combining the discrete element method (DEM) modules of the classic MFiX code (mfix.netl.doe.gov) with a modern low Mach number projection method for the continuous fluid phase. The new algorithm is implemented using the AMReX software framework for massively parallel block-structured applications (amrex-codes.github.io). This work utilizes a set of qualitative benchmarks which emphasize the phenomenology of a given problem rather than averaged statistical measures typically used in fluid-particle validation studies. The following cases are considered: 1) clustering of inelastic particles in the gas-solid homogeneous cooling system, 2) granular Rayleigh–Taylor instability of particles draining into a gas, 3) rapid injection of a single bubble into a particle bed at incipient fluidization, 4) ordered left-right bubbling pattern of a periodically fluidized bed, 5) segregation of "Brazil nuts" to the top of a small bed, 6) axial banding (segregation) of bi-disperse rotating tumbler. A range of agreement with the expected phenomena is observed and reported.