The Modelling of Compound Channel Flow: Physical Model of River Blackwater

This paper compares results derived from a physical model representing the River Blackwater, to numerical simulation using both a two-dimensional (2D) and three-dimensional (3D) model. The 2D model solves the shallow water depth-averaged continuity and Navier-Stokes equations with the depth-averaged form of the k −ε turbulence model for free surface flow. The 3D model solves the three-dimensional Reynolds-averaged continuity and Navier-Stokes equations with the renormalization group (RNG) k −ε turbulence model for steady-state flow. The model results are evaluated against the experimental data obtained from a 1:5 scale physical model of the River Blackwater, located at the UK Flood Channel Facility. The predicted distributions of the streamwise velocity, secondary vectors and bed shear stress are used to investigate the flow processes along the channel. The 2D and 3D model results show that the three-dimensional model predicts the flow fields much better than the two-dimensional model.