Influence of the fluid-mediated particle-particle force on sedimentation in an Euler-Lagrange framework

In liquid-particle flows for which the density of the two phases is comparable, particle-particle interactions can become increasingly important in systems involving sedimentation dynamics. In particular, the fluid-mediated particle-particle (PFP) force arising from these interactions plays a key role in influencing the bulk behaviour of the particle phase, with phenomena such as the formation of kinematic waves being markedly affected. Such effects are observed in both experiments and particle resolved direct numerical simulations (PR-DNS), however conventional Eulerian-Lagrangian (EL) models do not resolve pseudoturbulence and are unable to account for this behaviour. The present work addresses this using a closure for the pseudoturbulence contribution to the PFP force which is extracted from PR-DNS. Simulation results are compared against PR-DNS data, and highlight that inclusion of the PFP force in the EL framework is able to retrieve the behaviour of the particle velocity fluctuations observed in sedimentation processes across a range of values for particle volume fraction and Galileo number. Furthermore, it is also possible to identify the kinematic waves that are inherent to the system, demonstrating the necessity of incorporating the PFP force within EL models.