3D Numerical Simulation of the Separated Turbulent Shallow Flow around a Single Side Obstacle

In this paper, the performance of Reynolds Averaged Navier Stokes (RANS) simulations was evaluated to predict the flow structure developed by the presence of a sidewall obstruction in a uniform open-channel shallow flow. The study of these flow structures is important because they present in several real world configurations, such as groynes in rivers, where the erosion processes, mass transport, and influence of the flow hydrodynamics in ecological processes are still not well understood. Results of the numerical simulations were compared with the experimental laboratory measurements based on the Surface Particle Image Velocimetry (SPIV). It was found that the length of the main recirculation region obtained by two-equation models was 29% shorter than the measured one, while the predicted length by the Reynolds Stress Model (RSM) was in good agreement with the SPIV results. All of the performed RANS simulations were unable to predict properly the secondary separation region, which occurs immediately downstream of the side obstacle. This part of the flow field is a dead zone and due to extremely low velocity, the flow is laminar.