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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #357583
Research Project: Managing Water and Sediment Movement in Agricultural Watersheds

Location: Watershed Physical Processes Research

Title: Modeling internal erosion processes in soil pipes: capturing changing geometry dynamics

Author
item NIEBER, JOHN - University Of Minnesota
item Wilson, Glenn
item FOX, GAREY - North Carolina State University

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2019
Publication Date: 7/18/2019
Citation: Nieber, J., Wilson, G.V., Fox, G.A. 2019. Modeling internal erosion processes in soil pipes: capturing changing geometry dynamics. Vadose Zone Journal. 18:1.
DOI: https://doi.org/10.2136/vzj2018.09.0175

Interpretive Summary: The flow of water in a soil pipe and the resulting erosion of the inside walls of the soil pipe is simulated using a mathematical expression. This equation was coupled with an equation for transport of suspended sediment. The detachment of soil particles from the inside walls of the soil pipe was modeled by the well-known excess shear stress equation which represents particle detachment by the force of flowing water. The modeling results were compared to an experiment reported by Wilson (2011) in which water flowed into a soil pipe with the inflow maintained at a constant water level at the entrance. The simulated flow out of the soil pipe was found to be in close agreement with the measured outflow when roughness was imposed on the pipe wall. However, when the soil pipe was assumed in the model to be smooth walled, the simulated flow tended to be much greater than measured. The growth of the soil pipe with time due to erosion of the inside of the soil pipe was in good agreement with the experimental results when using soil erosion properties close to (within 20%) the value estimated by Wilson (2011). This work demonstrated a new method of predicting subsurface flow and soil loss from soil pipes.

Technical Abstract: The flow of water in a soil pipe and the resulting erosion of the soil pipe wall is simulated using a numerical solution of the Reynolds Averaged Navier-Stokes equations coupled with the equation for transport of suspended sediment. The well-known excess shear equation is used to model the detachment of particles from the soil pipe wall. The modeling results are compared to an experiment reported by Wilson (2011) in which the entrance to soil pipe constructed in a laboratory flume was subjected to a constant head of water in a reservoir. The modelled pipe discharge was found to be in close agreement with the measured results when roughness was imposed on the pipe wall. The temporal growth of the soil pipe was in good agreement with the experimental results when using a soil erodibility coefficient within 20% of the value estimated by Wilson (2011).