SQUARE-CYLINDER FLOW CHARACTERISTICS MODULATED USING UPSTREAM CONTROL ROD

The flow patterns, vortex-shedding frequency and aerodynamic performance of the square-cylinder flow were modulated using an upstream control rod. Additionally, the flow behaviors were examined using various Reynolds numbers, rotation angles, and spacing ratios. The flow patterns were visualized using the smoke-wire scheme. The global velocity fields and streamline patterns were analyzed using the particle image velocimetry (PIV). Additionally, the flow modes were characterized based on the kinematics theory. Moreover, the vortex-shedding frequencies behind upstream control rod and the square cylinder were detected using two hot-wire anemometers. The surface pressure on square cylinder was determined using a linear pressure scanner. Then, the aerodynamic parameters were calculated using the surface-pressure profiles. Three characteristic flow modes - single, attached, and bi-vortex-street - were categorized by varying the Reynolds number and spacing ratio. In the attached mode, the position of upstream control rod determined the flow characteristics. Furthermore, in the attached mode, the mean drag force of the square cylinder is about 57% lower than of single-square cylinder.