Flow Dynamics Around a Surface-Mounted Cube in Laminar and Turbulent Boundary Layers

The wake of a surface-mounted cube has been investigated by means of a large-eddy simulation, with the objective of describing the main characteristics of the dynamic flow under different boundary layers. A laminar boundary layer (LBL) with δ/D = 0.2 and a turbulent boundary layer (TBL) with δ/D = 0.8 have been considered. The spectral proper orthogonal decomposition was used to extract the main antisymmetric and symmetric modes of the flow. A low-order reconstruction using only the main antisymmetric mode pair revealed a closer location of the turbulent horseshoe vortex to the cube and the occurrence of reattachment on the cube’s side faces, which interfered with the vortex formation process for the TBL. Shed structures were composed mainly of streamwise strands, with a well-defined half-loop forming only at the beginning of the shedding process for the LBL. The main symmetric mode pair corresponded to a drift mode. It was found to control the length of the recirculation region in the near wake and the flow over the free end. The drift mode coefficients had a strong correlation with the normal force coefficient of the cube, especially for the LBL.