  MFiX-Exa is a new code being actively developed at Lawrence Berkeley National
Laboratory and the National Energy Technology Laboratory as part of the U.S.
Department of Energy's Exascale Computing Project. The starting point for the
MFiX-Exa code development was the extraction of basic computational fluid
dynamic (CFD) and discrete element method (DEM) capabilities from the existing
MFiX-DEM code which was refactored into an AMReX code architecture, herein
referred to as the preliminary MFiX-Exa code. Although drastic changes to the
codebase will be required to produce an exascale capable application,
benchmarking of the originating code helps to establish a valid start point for
future development. In this work, four benchmark cases are considered, each
corresponding to experimental data sets with history of CFD-DEM validation. We
find that the preliminary MFiX-Exa code compares favorably with classic
MFiX-DEM simulation predictions for three slugging/bubbling fluidized beds and
one spout-fluid bed. Comparison to experimental data is also acceptable (within
accuracy expected from previous CFD-DEM benchmarking and validation exercises)
which is comprised of several measurement techniques including particle
tracking velocimetry, positron emission particle tracking and magnetic
resonance imaging. The work concludes with an overview of planned developmental
work and potential benchmark cases to validate new MFiX-Exa capabilities.
