2021/06/14 by Jonathan Lemus, Lemus, Jonathan, Allan Fries +9 · 1 citation
Engineering · #Computational Physics (physics.comp-ph) #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Fluid Dynamics and Turbulent Flows #Lattice Boltzmann Simulation Studies #Particle Dynamics in Fluid Flows
paper · pdf · doi:10.48550/arxiv.2106.07694
openalex publication_date 2021/06/14 · openalex created_date 2022/07/25 · openalex updated_date 2026/07/28
Field observations and laboratory experiments have shown that ash\nsedimentation can be significantly affected by collective settling mechanisms\nthat promote premature ash deposition, with important implications for\nassociated impacts. Among these mechanisms, settling-driven gravitational\ninstabilities result from the formation of a gravitationally-unstable particle\nboundary layer (PBL) that grows between volcanic ash clouds and the underlying\natmosphere. The PBL destabilises once it reaches a critical thickness,\ntriggering the formation of rapid, downward-moving ash fingers that remain\npoorly characterised. We simulate this process by coupling a Lattice Boltzmann\nmodel, which solves the Navier-Stokes equations for the fluid phase, with a\nWeighted Essentially Non Oscillatory (WENO) finite difference scheme which\nsolves the advection-diffusion-settling equation describing particle transport.\nSince the physical problem is advection dominated, the use of the WENO scheme\nreduces numerical diffusivity and ensures accurate tracking of the temporal\nevolution of the interface between the layers. We have validated the new model\nby showing that the simulated early-time growth rate of the instability is in\nvery good agreement with that predicted by linear stability analysis, whilst\nthe modelled late-stage behaviour also successfully reproduces quantitative\nresults from published laboratory experiments.\n