Fluid structures in a shallow wake flow in an open channel

The mean features of the fluid structures present in the wake of a bluff body fixed vertically on the bed and normal to the flow direction in a shallow open channel flow are examined using numerical simulation with the Detached Eddy Simulation (DES) as a turbulence model. The Volume of Fluid (VOF) method is employed to resolve the water-air interface at the free surface. The first-order flat wave model in the STAR-CCM+ code is used to simulate the surface gravity waves on the interface. The fluid structures in the shallow wake are identified using the lambda(2)-criterion. Various distinctive structures are captured in the simulation which provide the three-dimensional signature of the shallow wake flow. The well-known horseshoe vortex and a system of parallel vortex tubes are observed in the near-bed region. Other types of structures are also detected close to the free surface, which are oriented both normal and parallel to the flow.