Investigation of Separated and Reattached Flow on a Blunt Flat Plate

The separated–reattached flow plays an important role in fluid transport and mixing; hence it is of practical relevance to the engineering community. Turbine blades, aircraft wings, structures, bridge piers, and heat sinks linked to electronic components are some of the potential places of application. In the present work, Direct Numerical Simulation (DNS) study has been carried out for flow past a long blunt plate placed along the flow direction. The finite difference representations are second-order accurate in time and space. The mesh is uniform in the cross-stream direction, while in both streamwise and wall-normal directions, a non-uniform mesh is used. The overall algorithm is time-explicit. Simulations are reported a Reynolds number (based on free-stream velocity and plate thickness) range of 400-1200. Results show that the flow experiences a series of temporal and spatial transitions with increasing Reynolds numbers. The flow field reaches a well-defined steady state at a low Reynolds number. However, the flow undergoes a Hopf bifurcation at around Re=415. It is also found that beyond a threshold value of the Reynolds number, the two-dimensional shear layers become three-dimensional, giving rise to hairpin structures. At Reynolds number close to the transitional value (Re=425), the flow reveals switching between two-dimensional and three-dimensional disturbances.