Two-Particle Sedimentation in Thermal Convection with Oscillating Boundaries: A Lattice Boltzmann Simulation

Abstract

The simulation framework captures full fluid-particle coupling while imposing controlled vertical oscillations (Strouhal number St = 0.01-100, Stokes number Sk = 0.01-10) on the wall of an enclosure. Through systematic comparison with static boundary cases, we quantify changes in: (1) Drafting-Kissing-Tumbling (DKT) sequence timing and intensity, (2) lateral migration patterns, (3) Nusselt number evolution, and (4) rotational dynamics via Magnus-to-drag force ratios.
Key findings demonstrate that wall oscillations induce measurable modifications while preserving Grashof-determined regime characteristics. At Gr = 564, boundary oscillations suppress particle collision compared to the static wall collision at 𝑡 ∗ = 120.7, and increase lateral displacements by ~30%. The moderate Gr = 2500 case shows the most significant response, with collisions advancing to 𝑡 ∗ = 42.99 compared to the static wall case at 𝑡 ∗ = 53.67 and Magnus forces decreasing by 50%. High thermal forcing at Gr = 4500 reveals the limits of boundary control, while oscillations introduce a collision at 𝑡 ∗ = 114.67 and slightly regularize trajectories, the dominant wall-driven chaos persists with
The thesis contributes to the fundamental understanding of mixed convection-particle systems while offering practical insights for industrial applications ranging from microfluidic devices to large-scale sedimenters. Future work could extend this framework to three-dimensional systems, polydisperse particles, or active feedback control scenarios.

Date of Award	2025
Original language	American English
Supervisor	Eiyad Abu-Nada (Supervisor)