Flow characteristics around juncture of a circular cylinder mounted normal to a flat plate

To study the flow characteristics in the upstream and downstream regions around the juncture of a long circular cylinder and a flat plate, experiments by particle-tracking flow visualization method and particle image velocimetry (PIV) were performed in a towing water tank. The Reynolds numbers were from 500 to 6000 and the inverse of non-dimensional boundary-layer displacement thickness were within 3.47-12.03. The temporal and spatial evolution processes of the vortical flow structures in the vertical and horizontal planes in the upstream and downstream regions around the juncture of a long circular cylinder and a flat plate were revealed. The flow patterns delineated by velocity vectors and streamlines were discussed for their topological flow characteristics. The unsteady features of the wake near the juncture were presented. Four characteristic flow modes (single-vortex, dual-vortex, triple-vortex, and unsteady-vortex) induced by the boundary-layer separation and shear effect of the counter flow near the juncture were observed in the upstream region near the juncture. The magnitude of the wall-shear stress under the vortex ring nearest the juncture presented the largest value. In the cylinder wake, no periodic vortex shedding was observed at the levels influenced by the upstream horse-shoe vortex rings. Above the region influenced by the upstream horse-shoe vortex rings, the vortex shedding presented periodic characteristics with a Strouhl number of approximately 0.2.