**2. Materials and Methods**

Two methods of Lagrangian tracking of particles in fluid flow, available as part of ANSYS Fluent, a commercial computational fluid dynamics (CFD) software, were used in this work. The first is the discrete phase model (DPM) [23], in which the particles are assumed to be point masses, and their volume is not accounted for in the equations of fluid flow. The second is the dense discrete phase model (DDPM) [23], in which the volume of particles are accounted for in the governing equations of fluid flow via their volume fraction. Within the DDPM framework, particle–particle interaction can be included. Multiple approaches are available to describe particle–particle interaction; in this work, this interaction is investigated via the discrete element method (DEM). To this end, an additional DEM software is used, Altair EDEM, and connected to ANSYS Fluent to exchange information about particles.
