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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/nhess-2017-258
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
17 Jul 2017
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Natural Hazards and Earth System Sciences (NHESS).
Comparing Thixotropic and Herschel-Bulkley Models for Avalanches and Subaqueous Debris Flows
Chan-Hoo Jeon1,2 and Ben R. Hodges2 1Division of Marine Science, The University of Southern Mississippi, 1020 Balch Blvd, Stennis Space Center, Mississippi 39529, USA
2Center for Water and the Environment, The University of Texas at Austin, Austin, Texas 78712, USA
Abstract. Debris flows such as avalanches and landslides are heterogeneous mixtures of solids and liquids but are often simulated as homogeneous non-Newtonian fluids using a Herschel-Bulkley model. By representing the heterogeneous debris as a homogeneous non-Newtonian fluid, it is possible to use standard numerical approaches for the Navier-Stokes equations where viscosity is allowed to vary in time and space (e.g. eddy-viscosity turbulence models). Common non-Newtonian models are time-independent so that the relationship between the time-space-varying effective viscosity and flow stress is unchanging. However, the complex behaviors of debris flows at flow initiation (jamming) and cessation (restructuralization) imply that the viscosity-stress relationships should have time-dependent behaviors, which is a feature of thixotropic non-Newtonian fluids. In this paper, both Herschel-Bulkley and thixotropic non-Newtonian fluid models are evaluated for simulating avalanches along a slope and subaqueous debris flows. A numerical solver using a multi-material level set method is applied to track multiple interfaces simultaneously. The numerical results are validated with analytical solutions and available experimental data using parameters selected based on the experimental setup and without post-hoc calibration. The thixotropic (time-dependent) fluid model shows reasonable agreement with all the experimental data. For most of the experimental conditions, the Herschel-Bulkley (time-independent) model results were similar to the thixotropic model, a critical exception being conditions with a high yield stress. Where the flow initiation is strongly dominated by the structural jamming and the initial yield behavior the time-independent model performed poorly.

Citation: Jeon, C.-H. and Hodges, B. R.: Comparing Thixotropic and Herschel-Bulkley Models for Avalanches and Subaqueous Debris Flows, Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2017-258, in review, 2017.
Chan-Hoo Jeon and Ben R. Hodges
Chan-Hoo Jeon and Ben R. Hodges
Chan-Hoo Jeon and Ben R. Hodges

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Short summary
This work shows that a multiphase flow solver using a multi-material level-set method with yield-stress models of non-Newtonian viscosity provides a means for numerical approximation of avalanches and subaqueous mudslides. This simulation approach was tested with both time-independent and time-dependent models of viscosity. Moreover, two different approaches were used to evaluating the Coussot parameters. Overall, the numerical results showed reasonable agreement with prior experimental data.
This work shows that a multiphase flow solver using a multi-material level-set method with...
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