Performance of Three-Dimensional Modeling for Flow Structures in Channel Bends

Abstract

Natural channels are seldom straight and commonly take sinuous patterns with turbulent and strongly three-dimensional (3D) flows in the bends. A 3D hydrodynamic model [Reynolds-averaged Navier-Stokes (RANS)] with major 3D flow features and different turbulence submodels was developed in a curvilinear, nonorthogonal coordinate system. A typical consecutive bend experiment was chosen as the verification case. A bend flow characteristic model with two turbulence submodels (k-ε and shear-stress transport model) was developed using different grid mesh systems. A comparative assessment of the models was performed. The model verification was conducted by comparing the simulated velocity distribution, flow structure, and secondary current development with the experimental measurements. Differences between the simulations and measurements were observed when the secondary current or separation layer occurred. This indicates that the simulation accuracy in the high-sinuosity bends decreases with the development of channel bends. Comparison of the results obtained by the 3D RANS model with experimental and field data, and numerical predictions, validates that the k-ε model with the fine-grid system is capable of simulating flow fields in curved open channels with reasonable accuracy.