Simulation of Turbulent Particulate Flows for Nuclear Waste Management: Agglomeration in Vertical Flows

Results from large eddy simulations of relevance to the transport of nuclear waste flows are analysed to elucidate the interaction between the turbulent flow and calcite particles (a nuclear waste test material) in vertical flows. Agglomeration of particles is modelled based on the hard-sphere collision approach coupled to van der Waals' interaction in a Lagrangian framework. The number density of particle collision frequency, efficiency and agglomeration rate reveal the importance of gravity, lift and buoyancy forces in the simulations. The number of collisions increases in the order of upward, no gravity and downward flows, whereas the reverse occurs for the number of agglomerations. The upward flow shows a higher agglomeration rate than the other flows due to the depletion of particles in the near-wall region under the action of the lift force.