Three-dimensional numerical model of lateral-intake inflows

A three-dimensional (3D) numerical model for predicting steady, in the mean, turbulent flows through lateral intakes with rough walls is developed, validated, and employed in a parametric study. The method solves the Reynolds-averaged Navier-Stokes equations closed with the isotropic k-omega turbulence model of Wilcox, which resolves the near-wall flow and accounts for roughness effects in a straightforward manner. Calculations are carried out for flows through rectangular closed-duct and open-channel T-junctions. Comparisons of the predicted mean velocity field with laboratory measurements indicate that the model captures most experimental trends with reasonable accuracy. For the parametric study, hows are predicted for a range of discharge ratios, aspect ratios, and main channel-bed-roughness distributions. The numerical solutions are examined to elucidate the complex 3D flow patterns of lateral-intake hows, including zones of how division, separation and reversal, vortices, and singular points within the bed-shear stress vector field. The model reproduces known 3D flow patterns and provides novel insights about the complex hydraulics and sediment transport processes encountered in lateral intakes at a level of detail that is not attainable by laboratory studies alone.