Particle-resolved simulations of settling particles: A methodology for long time-integration intervals

TL;DR

This paper introduces a novel simulation methodology for dilute particle suspensions that overcomes vertical periodicity limitations, enabling long-term, efficient simulations and new physical insights into particle dynamics.

Contribution

The authors develop a moving reference frame approach that removes vertical periodicity, allowing for long-time simulations of particle settling without core solver modifications.

Findings

Achieved a 600 D/U_g simulation interval for many particles, the first of its kind.

Enabled exploration of fluid effects on particle layers and flow turbulence post-passage.

Demonstrated the method's ease of implementation with minimal parameter tuning.

Abstract

We present a methodology for simulating dilute suspensions of particles settling under gravity, with the main purpose of overcoming limitations of triply periodic configurations, mainly the strong vertical correlation that hinders the study of cluster dynamics. The current approach removes vertical periodicity and employs a moving reference frame, enabling efficient simulations of both single- and many-particle cases. We illustrate the method with two examples of increasing complexity: a single particle in the steady vertical regime, and a many-particle case at a parametric point where collective effects were previously observed and recovered here. A converged, free-of-corrections time interval of approximately $600 D/U_g$ is simulated in the many-particle case, representing the first simulation of this kind to date. New physical insights can be explored thanks to this new configuration, for example the effect of still fluid on the first layer of particles encountered by the fluid, or the turbulent character of the flow after a swarm of particles has passed by. Finally, the method only requires parameter tuning, allowing implementation within existing solvers without changes to their core formulation: for a standard configuration with an imposed free stream velocity at the inlet, only the input velocity (or the viscosity of the fluid) and the time step need to be updated.