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Experimental Investigation into the Number of Phases in Debris Flows

by Bin Li and Ze-Min Xu

Appl. Sci. 2025, 15(8), 4282; https://doi.org/10.3390/app15084282 - 13 Apr 2025

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Controversial number of phases in debris-flow masses involves almost all areas of debris-flow research. In this study, we experimentally investigated the number of phases in fully developed debris flows using six sediments with three maximum diameters of up to 30 mm from two representative debris-flow deposits in China. Fluid escape tests, displacement experiments, relative motion experiments, and rheometrical tests were conducted using 12 slurries prepared with the sediments. The results from four types of experiments show that debris flows are close to one-phase flow and far from two-phase flow. Under both gravity and artificial hydraulic and mechanical forcing, no relative motion of water or fluid composed of water and fine-grained particles and solids occurs in both the experimental flows and static slurries. This suggests that the water and solids in debris flows move together as a single fluid, and are deposited by “freezing”. The rheological behavior of the experimental debris flows is similar to that of Bingham materials. This indicates that debris flows may be approximated as continuous, homogeneous, isotropic fluids. In conclusion, debris flows behave more like monophasic flow, are far from biphasic flow, and should be treated as one- rather than as two-phase flow. Full article

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23 pages, 7677 KiB

Open AccessArticle

Modeling the Slump-Type Landslide Tsunamis Part II: Numerical Simulation of Tsunamis with Bingham Landslide Model

by Thi-Hong-Nhi Vuong, Tso-Ren Wu, Chun-Yu Wang and Chia-Ren Chu

Appl. Sci. 2020, 10(19), 6872; https://doi.org/10.3390/app10196872 - 30 Sep 2020

Cited by 6 | Viewed by 2964

Abstract

This paper incorporates the Bingham rheology model with the Navier–Stokes solver to simulate the tsunamis excited by a slump-type landslide. The slump is modeled as the Bingham material, in which the rheological properties changing from the un-yield phase to yield phase is taken into account. The volume of fluid method is used to track the interfaces between three materials: air, water, and slump. The developed model is validated by the laboratory data of the benchmark landslide tsunami problem. A series of rheological properties analyses is performed to identify the parameter sensitivity to the tsunami generation. The results show that the yield stress plays a more important role than the yield viscosity in terms of the slump kinematics and tsunami generation. Moreover, the scale effect is investigated under the criterion of Froude number similarity and Bingham number similarity. With the same Froude number and Bingham number, the result from the laboratory scale can be applied to the field scale. If the slump material collected in the field is used in the laboratory experiments, only the result of the maximum wave height can be used, and significant errors in slump shape and moving speed are expected. Full article

(This article belongs to the Special Issue Numerical Simulation of the Tsunami Propagation)

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