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Multiphase Modeling of Density Current Interactions with Topography: Insights into Depositional Processes

Brandon Keim1, Mattia de\' Michieli Vitturi2, Greg Valentine1, Amanda Clarke3, Rupa Ragavan3, Elishiva Sherman3

  • Affiliations: 1 Department of Geology, University at Buffalo, Buffalo, NY, USA, 2 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, Pisa, Italy 3 School of Earth and Space Exploration, Arizona State University, Tempa, AZ, USA

  • Presentation type: Talk

  • Presentation time: Friday 15:00 - 15:15, Room R380

  • Programme No: 3.9.4

  • Theme 3 > Session 9

Abstract

Understanding pyroclastic density currents (PDCs) requires addressing their complex interactions with topography, where flow dynamics, turbulence, and sedimentation processes vary significantly. We employ a novel multiphase OpenFOAM solver to simulate flume experiments replicating dilute PDC behavior and interactions with topography. The high-resolution, parallel simulations inject a water-alcohol mixture, along with multiple particle classes, into domains featuring simple topographies such as flatbeds, hills, and valleys. Buoyancy reversal, induced by particle sedimentation and the alcohol-water mixture's lower than ambient density, effectively mimics key dynamics of natural PDCs, including their transport and deposition. We compare our simulation results to notable features, such as climbing dunes and variations in deposit thickness on stoss and lee slopes from experimental flume runs.  Our simulations also incorporate multiple particle size classes and time-varying inlet conditions, which better replicate natural geological scenarios. By integrating experimental and numerical approaches, this work provides critical insights into how PDCs interact with and are influenced by complex topography. While the current focus is on water-based flows, the methodology is adaptable to dilute PDCs, as well as turbidity currents, since the main non-dimensional numbers characterizing these experimental and simulated flows are in the range of real PDCs. These results advance our ability to interpret flow dynamics from deposits, contributing to the broader understanding of pyroclastic surge behavior, sedimentation processes, and flow interactions with topographic obstacles. Ultimately, this work aids in refining volcanic hazard assessments and reconstructing PDC dynamics in diverse geological settings.