Large-eddy simulations of the flow over a semi-circular cylinder at Re = 50000

Large-eddy simulations (LES) of the flow over a semi-circular cylinder at a diameter-based Reynolds number 50000 and zero angle of attack are presented. In comparison with the prominent benchmark flows past circular and square cylinders, this test problem has been less investigated in the literature from both numerical and experimental perspectives. Also, this case can be even more challenging for validation and verification of the computational codes due to a negative lift force, which characterizes this flow regime. A standard numerical platform based on a second-order finite volume method and the -equation eddy viscosity subgrid scale model and its dynamic version, implemented in the OpenFOAM CFD toolbox, is used for the present LES. A detailed spectral analysis is provided to examine dynamics of the vortex shedding and shear layer instabilities. The moderate Reynolds number is chosen in order to replicate experimental data, which is limited to integral flow parameters like the lift, drag and pressure coefficients and a Strouhal number. The numerical and experimental data available for the flows over the circular and square cylinders at the Reynolds number are used for qualitative assessment of the present results. Similarity of the turbulent wakes between the circular, square and semi-circular cylinders are discussed and compared both, for the integral flow parameters and high order statistics as well. Overall, present simulations provide reasonable agreement with available measurements and numerical calculations. Consistency and satisfactory agreement with the previous numerical and experimental results obtained for the circular and square cylinders are shown as well