Three-Dimensional Simulation Parameters for 90° Open Channel Bend Flows

Sharp open channel bend flows are highly three-dimensional because of the combined effects of secondary flow, large free-surface variations, and flow separation along the inner bend wall. A comprehensive analysis was performed to determine the best modeling parameters to study the open channel sharp bend flow. Comparisons of the simulation results were made from two commercial codes, three turbulence models [k-ε renormalization group (RNG), Reynolds stress model (RSM), and large eddy simulation (LES)], two flow domain representations [Cartesian and body-fitted coordinate (BFC) grids], and three water surface treatments [rigid lid, porosity, and volume of fluid (VOF)]. Based on a comparison with experimental data, the best results were obtained with software using the RSM and VOF approach. Adequate representation of counter-rotating secondary flow cells in the channel downstream of the bend requires both the appropriate treatment of the channel free surface and a turbulence model that can resolve the anisotropy of turbulence.