This paper investigates and compares the effect of a solid, spherical particle phase on surrounding carrier fluids (air and water) in a turbulent channel flow. The fluid phase properties are chosen to represent a flow typical of the nuclear waste industry, with the flow modelled using the direct numerical simulation (DNS) code, Nek5000, at a shear Reynolds number of 180. A Lagrangian particle tracker is developed and implemented to simulate the dispersed phase, capable of accommodating two-way coupling between the fluid and discrete phase and inter-particle collisions (four-way coupling). In order to investigate the effect that the four-way coupled particulate phase has on the turbulence field, mean fluid velocities and turbulence intensity statistics are recorded. The work demonstrates that the introduction of two-way coupling does indeed impact slightly on the turbulence field. Specifically, it reduces the mean velocity profile and increases the streamwise turbulence intensity in the near-wall region. Upon the introduction of inter-particle collisions, the flow statistics studied show a negligible response. Collision density distributions are studied and a temporal migration to the near-wall region is observed. Along-side this, to investigate particle density-ratio effects, water-based results are contrasted with simulations in air. The way in which the flow statistics are modified are shown to differ in air and water. Finally, a DLVO agglomeration model is demonstrated, whereby particles colliding with enough energy to overcome the potential barrier are considered bound. This is applied to the four-way coupled flow with temporal distributions of agglomerate counts presented
