Impact of planar shear inflow on wake behind a normal flat plate

This study employs a direct numerical simulation to analyze the effects of planar shear inflow on the flow characteristics around a normal flat plate. The influence of shear is examined by comparing it with a uniform inflow condition. Based on the centerline inflow velocity and plate height, the Reynolds number was taken as 170 and the non-dimensional shear rate as 0.1. Flow visualization shows that the wake from uniform inflow is experiencing a temporal beating phenomenon that switches between coherent and incoherent states, whereas the planar shear drives the flow toward a fully incoherent state. A comparison with the uniform inflow case shows that planar shear induces weaker vortex shedding, a lower drag coefficient, and a corresponding increase in the recirculation length. Furthermore, a phase-time analysis using the Hilbert transform revealed that the vortices are shed in-phase in the uniform inflow case, whereas they are mostly out-of-phase in the planar shear case. Reduction of coherent vortices and enhancement of incoherent fluctuations are evident in the planar shear case, thereby affecting the mean velocity and Reynolds stress symmetry and a modest increase in the magnitude of turbulent components.