Solid Particle Interaction Dynamics at Critical Stokes Number in Isotropic Turbulence

Abstract

Binary solid spherical particle-particle interactions are studied in forced isotropic turbulence at = 29 and 197 using direct numerical simulation and an immersed boundary method. Isotropic turbulence in a periodic box is forced using a linear forcing method to maintain statistically stationary turbulence, with inter-particle interaction modelled using DLVO interaction forces which include attraction and repulsion due to van der Waals and electric double layer potential forces, respectively. Particle collisions are modelled using the inelastic hard sphere model with a coefficient of restitution of 0.4. The DLVO parameters are chosen to be representative of calcite particles, a simulant of nuclear waste material found in storage ponds in the UK. The Reynolds numbers chosen for the boxes are equivalent to typical values of that are found in the bulk flow and viscous sub-layer regions of a turbulent channel flow at =180. The techniques described are used to study the dynamics of critical Stokes number particles in turbulence by analysing probability density functions (PDFs) of collision statistics such as particle displacement and the particles’ relative velocities to determine the likelihood of agglomeration. The results indicate that agglomeration can occur in both the turbulent boxes considered. However, the occurrence is much more likely at lower values due to the higher dispersion of kinetic energy after impact