Characteristics of the wake flow control behind two side-by-side circular cylinders by a small cylinder

Vortex shedding passive control of two side-by-side circular cylinders has been experimentally investigated. The transverse spacing between the two main cylinders is 1.5D, where D is the diameter of the cylinder. The Reynolds number based on the cylinder diameter is 5 900. A small circular cylinder being parallel to the main cylinders was used as a controller, which was placed on the flow centreline L = 0-2D behind the main cylinders. Hot wire anemometry was used to measure the instantaneous velocity fluctuations at the plane of 10D downstream of the main cylinders. The wall static pressure around the main cylinders was measured for all the configurations. It is found that while the small cylinder was placed in the close vicinity of the main cylinder, say L/D less than or equal to 0.5, vortex shedding process was controlled very well, and the flow field was symmetric. At L/D greater than or equal to 1.0, the small cylinder was unable to suppress the occurring of wide-narrow wake.