Effects of dual connected vertical plates on flow features of a single square cylinder

This study investigates the efficacy of two connected vertical flat plates, utilized as controlling devices, to suppress the fluid forces by averting the vortex shedding around a square cylinder. Such fluid flow controlling strategy has been very less adopted in past. It consists of two identical controlling plates fitted to the top and bottom sides of a square cylinder within the framework of a passive flow control gadget. The height of control plates (l) progressively varied from 0.1 to 3.75 times the cylinder’s size with a fixed width of 0.2 times cylinder’s size. Through this strategy, complete control of flow is achieved much earlier at smaller heights of plates as compared to the conventional passive control strategies. With the growing height of the plates, a trio of flow patterns appeared in the wake of cylinder: unsteady flow within l = 0.1–1.4, transient flow within l = 1.5–2.6 and steady flow for l ≥ 2.7. The streamlines exhibit various shape structures in the wake depending on the heights of the control plates. Such flow structures are referred to as an oval shaped structure for l = 0.1–1.1, an extended sized vortex for l = 1.2–1.7, a D-type structure for l = 1.8–2.2 and an ellipse like structure for l = 2.4–3.75. The control plates are found efficient in controlling the vortex shedding, the Strouhal number and amplitude of fluctuating drag as well as altering the base pressure at all the heights while the amplitude of lift, the rms value of drag and the lift tend to reduce as plates’ height reached the value 2.2.