Numerical Simulation of the Agglomeration Behaviour of Spheroidal Particle Pairs in Chaotic Flows

Interactions between attractive spheroidal particles are studied in boxes of chaotic flow under the action of a homogeneous and isotropic forcing technique. The fully resolved fluid field and structure-resolved particle-fluid coupling regime are obtained through direct numerical simulation and an immersed boundary method. Agglomeration outcomes are accommodated through attractive van der Waals forces, suitably adapted to consider the orientational dependencies associated with the non-spherical shape. Binary particle interactions are first studied in quiescent conditions, as well as in a periodic box of chaotic fluid flow. The latter is forced using a stochastic method, where the magnitude of the velocity fluctuations and Taylor-Reynolds number are chosen based on those typically seen in nuclear waste processing scenarios. Differences in particle interaction behaviours are presented for the cases of disks and needles, with the role of orientation and kinetic energy in determining interaction outcomes analysed and contrasted with spheres. Results indicate that needles have the highest agglomeration propensity in the chaotic fluid, followed by spheres, and then disks. Lastly, the inclusion of attractive orientationally-dependent interaction forces promotes alignment between the symmetry axes of spheroidal particle pairs, whilst the increased action of the fluid was also seen to promote alignment between the interacting particles when compared to the quiescent case.