DES evaluation of near-wake characteristics in a shallow flow

Three-dimensional numerical modeling using Detached Eddy Simulation (DES) based on unsteady Reynolds-Averaged Navier–Stokes (RANS) with the k–ω SST (Shear-Stress Transport) turbulence model has been carried out to evaluate the characteristics of a shallow wake flow. The shallow wake is generated by inserting a sharp-edged bluff body in the open channel flow. A horseshoe vortex is captured in front of the body, which stretches downstream and envelops the vortices that form part of the shear layers. The mean and instantaneous flow field characteristics in the wake are examined and compared at different downstream locations to evaluate the three-dimensional features in the flow. Streamwise positive directed velocity is observed in the wake centerline at horizontal planes close to the bed. Flow features hitherto not captured in experimental studies can be identified in sections parallel to the bed and body. A typical signature of three-dimensionality, upward ejection of fluid elements from the bed towards the free surface, is also observed in the wake.