Wake of a Circular Cylinder in Flowing Soap Films

Flow past a stationary circular cylinder is studied experimentally in an inclined flowing soap film. Experiments are conducted in the low Reynolds number regime (Re < 200). Images acquired using a high-speed camera are used to study the global wake structure of the circular cylinder for different Reynolds numbers. Both the near-wake and the far-wake are closely observed for the variation of wake characteristics such as recirculation bubble length, shedding frequency of the vortices, and the intervortex spacing of von Karman vortex street with the soap solution's volumetric flow rate. As the flow rate rises, the wavelength of the vortices first increases, reaches a maximum, and then decreases. The ‘b/a’ ratio (the ratio of the distance between clockwise and counterclockwise vortices to the distance between two successive vortices in the same row) remains constant for large parts of the flow regime studied.