EP013-0003
Quantifying the role of fluid viscosity on bed force distributions in multiphase granular flows

Tuesday, 8 December 2020
Poster
Amelia Winner, University of Oregon, Eugene, OR, United States, Ken Ferrier, University of Wisconsin Madison, Madison, WI, United States, Josef Dufek, University of Oregon, Earth Sciences, Eugene, OR, United States, Eric Breard, University of Oregon, Department of Earth Sciences, Eugene, OR, United States and Scott W McCoy, University of Nevada Reno, Reno, NV, United States
Abstract:

Granular flows occur in a wide variety of geologic settings and can vary greatly in behavior, ranging from high energy gravity currents to creeping flows. As these flows move, they impose forces on their underlying bed, the magnitude and frequency of which is determined by internal granular dynamics. The granular dynamics of these flows are influenced internally by the physical properties of the grains as well as the properties of the interstitial fluid, the latter of which may dampen particle collisions due to increased particle-fluid coupling, can contribute to particle sorting, and may modify pore pressure in concentrated regions of flow. Therefore, in order to predict the distribution of forces imposed on the bed by a granular flow, it is necessary to understand the role of the fluid component in modifying particle interactions. Here, we report findings on the sensitivity of bed force probability distributions to the interstitial fluid viscosity for simulated granular flows within a rotating cylindrical flume. We explore flows with Stokes numbers ranging from 10-5 to 105 and inertial numbers ranging from 10-4 to 101. The bed force distributions generated from these simulated flows are generally well fit by the generalized Pareto distribution. Our results suggest that the length of the tail of the probability distribution of bed forces increases with mean grain size and shear rate, and decreases with fluid viscosity. The results of this work also highlight the importance of capturing fluid-particle interactions even for low viscosity fluids (~10-5 Pa s). For example, neglecting to include air as an interstitial fluid for dry flows can lead to overestimation in the frequency of high magnitude bed force excursions by a factor of 4. Ultimately, results from these simulations can help provide a basis for understanding the influence of fluid and solid phase properties on bed force distributions and inform our understanding of granular flow behavior in natural and industrial settings.

<< Previous Abstract | Next Abstract >>