A depth-averaged two-phase model for debris flows over fixed beds |
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| Authors: | Ji Li Zhixian Cao Kaiheng Hu Gareth Pender Qingquan Liu |
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| Institution: | 1. State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China;2. Institute for Infrastructure and Environment, Heriot-Watt University, Edinburgh Campus, Edinburgh EH14 4AS, UK;3. Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China.;4. Department of Mechanics, Beijing Institute of Technology, Beijing 100081, China |
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| Abstract: | A depth-averaged two-phase model is proposed for debris flows over fixed beds, explicitly incorporating interphase and particle-particle interactions, fluid and solid fluctuations and multi grain sizes. A first-order model based on the kinetic theory of granular flows is employed to determine the stresses due to solid fluctuations, while the turbulent kinetic energy - dissipation rate model is used to determine the stresses from fluid fluctuations. A well-balanced numerical algorithm is applied to solve the governing equations. The present model is benchmarked against USGS experimental debris flows over fixed beds. Incorporating the stresses due to fluid and solid fluctuations and properly estimating the bed shear stresses are shown to be crucial for reproducing the debris flows. Longitudinal particle segregation is resolved, demonstrating coarser sediments around the fronts and finer grains trailing the head. Based on extended modeling exercises, debris flow efficiency is shown to increase with initial volume, which is underpinned by observed datasets. |
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| Keywords: | Debris flow Two-phase model Depth-averaged model Fluctuation kinetic energy Multi grain sizes |
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