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Numerical simulations of a fluidized granular flow entry into water: insights into modeling tsunami generation by pyroclastic density currents

Abstract : The tsunami generation potential of pyroclastic density currents (PDCs) entering the sea is poorly understood, due to limited data and observations. Thus far, tsunami generation by PDCs has been modeled in a similar manner to tsunami generation associated with landslides or debris flows, using two-layer depth-averaged approaches. Using the adaptive partial differential equation solver Basilisk and benchmarking with published laboratory experiments, this work explores some of the important parameters not yet accounted for in numerical models of PDC-generated tsunamis. We use assumptions derived from experimental literature to approximate the granular, basal flow component of a PDC as a dense Newtonian fluid flowing down an inclined plane. This modeling provides insight into how the boundary condition of the slope and the viscosity of the dense granular-fluid influence the characteristics of the waves generated. It is shown that the boundary condition of the slope has a first-order impact on the interaction dynamics between the fluidized granular flow and water, as well as the energy transfer from the flow to the generated wave. The experimental physics is captured well in the numerical model, which confirms the underlying assumption of Newtonian fluid-like behaviour in the context of wave generation. The results from this study suggest the importance of considering vertical density and velocity stratification in wave generation models. Furthermore, we demonstrate that granular-fluids more dense than water are capable of shearing the water surface and generating significant amplitude waves, despite vigorous overturning.
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https://hal.archives-ouvertes.fr/hal-03419617
Contributor : Stéphane Popinet Connect in order to contact the contributor
Submitted on : Monday, November 8, 2021 - 3:50:39 PM
Last modification on : Tuesday, November 16, 2021 - 5:27:29 AM

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Lily Battershill, Colin Whittaker, Emily Lane, Stéphane Popinet, James White, et al.. Numerical simulations of a fluidized granular flow entry into water: insights into modeling tsunami generation by pyroclastic density currents. Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2021, ⟨10.1029/2021jb022855⟩. ⟨hal-03419617⟩

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