Flow past a blunt flat plate subjected to the disturbance of incident vortex street

An experimental investigation was conducted to study the flow past a square leading-edge flat plate subjected to the disturbance of a Karman vortex street. The experiments were carried out in a wind tunnel using flow visualization together with surface pressure measurements, at a Reynolds number of 1000 based on the plate thickness. The incident vortex street was generated by employing a symmetrical airfoil located at a certain distance upstream of the test plate. The vertical offset between the incident vortex street and the plate was varied in the range 0–5 of plate thicknesses. It was found that at small vertical offsets, the incident vortices were distorted or split by the presence of the plate and secondary vortex shedding from the leading edge was induced, resulting in a sharp rise in mean pressure distribution immediately downstream of the leading edge. At large vertical offsets, the incident vortices preserved their coherence when passing over the plate and the separated shear layer was observed reattaching to the plate surface at a more downstream position as the vertical offset was increased. The pressure measurements also reflected the variation of the reattachment length with the vertical offset.