Oscillatory motion of two confined interacting particles settling under thermal convection: A lattice Boltzmann study

This study investigated the sedimentation of two oscillating cold circular particles within a confined heated channel using the lattice Boltzmann method. The main objective was to investigate the effects of mixed convection, initial particle positioning, and wall confinement on particle behavior under different thermal regimes. In particular, this work sought to explain the mutual interactions between particles in the presence of these effects. Such an investigation is highly significant due to its widespread relevance in various natural and industrial processes involving particle transport. The four-way coupled model was validated against several classical benchmarks, including the drafting-kissing-tumbling interaction. The results demonstrated the critical role of initial particle positioning in promoting oscillatory motion. The reattachment of particle wakes leads to pronounced oscillations and vortex shedding in the trailing particle, especially when the particles are close. While these oscillations enhance the heat transfer coefficient, inter-particle collisions tend to suppress it. The results further revealed a decrease in the average Nusselt number for both particles below two, suggesting potential overestimation in the literature's correlation models. Furthermore, the Magnus force increasingly dominates drag forces as the Grashoff number increases. Notably, the influence of the trailing particle on the leading particle was observed exclusively during particle-wall collisions when close to the leading particle. Overall, this study highlighted the significant impact of thermal forces with wall confinement on particle motion across various thermal regimes, providing valuable insights into complex particle behavior and sedimentation patterns.