  In this work, a new partition-collocation strategy for the parallel execution
of CFD--DEM couplings is investigated. Having a good parallel performance is a
key issue for an Eulerian-Lagrangian software that aims to be applied to solve
industrially significant problems, as the computational cost of these couplings
is one of their main drawback. The approach presented here consists in
co-locating the overlapping parts of the simulation domain of each software on
the same MPI process, in order to reduce the cost of the data exchanges. It is
shown how this strategy allows reducing memory consumption and inter-process
communication between CFD and DEM to a minimum and therefore to overcome an
important parallelization bottleneck identified in the literature. Three
benchmarks are proposed to assess the consistency and scalability of this
approach. A coupled execution on 280 cores shows that less than 0.1% of the
time is used to perform inter-physics data exchange.
