Predicting 3-D flows at lateral water intakes

This paper demonstrates the predictive capabilities of a three-dimensional Computational Fluid Dynamics (CFD) model for lateral intake flows. The model solves the Reynolds-averaged Navier-Stokes (RANS) equations in orthogonal curvilinear coordinates. The near-wall k-ω model is employed for turbulence closure. Calculations are carried out for flow through a 90 degree rectangular diversion and the results are compared with available experimental measurements. The computed solutions are further analyzed to elucidate the complex three-dimensional separation and limiting streamlines patterns. It is shown that the bottom solid boundary and the surrounding side walls induce a complex three-dimensional flow which includes: a depth varying dividing stream-surface in the main channel; depth varying flow separation and reversal zones in both main and branch channels; and transverse circulation currents which sweep near-bottom flow into the zones of flow reversal. These same flow patterns have been observed experimentally for both turbulent and laminar flow regimes, but their details were not reported in previous numerical studies.