engleski

A 3D Numerical Model of Two-Phase Flow and Sediment Transport

A 3D numerical model for calculating two-phase flow and sediment transport with sand bed deformation is presented in this study. Two- phase incompressible and viscous flow model is based on the existing Finite Volume numerical model. The Volume of Fluid (VOF) method is used for interface capturing. Turbulence modelling is done using the k − ω SST model. Suspended-load transport of sediment is simulated through a general convection-diffusion equation. The settling velocity is determined by empirical correlations. The bed load transport is incorporated directly into the Exner equation, which is used to calculate sand bed elevation changes. The Exner equation is solved numerically using the Finite Area Method. Net deposition and entrainment rates are calculated separately, where entrainment rate is calculated using the van Rijn model. The mesh deformation is performed by automatic mesh motion solver, which calculates the motion of internal points based on the calculated motion of bed boundary points by solving the variable diffusivity Laplace equation. The Laplace equation is discretised using the finite element method. The validation of the model is carried out on several test cases. The suspended-load model is validated by calculating the flow in a straight channel with net deposition of suspended load and fixed bed, and the full 3D total-load model is validated by calculating the flow and sediment transport in 140 and 180 degrees channels with movable bed. In all cases, the agreement with the experimental data is good.

Sediment Transport ; Scour ; Two Phase Flow ; Mesh Motion ; OpenFOAM

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