Flow structures around a single circular cylinder and tandem cylinders near wall

In this study, a comparative study of the flow structure formed by changing the distance between two consecutively placed circular cross-section cylinders and the base was investigated experimentally using the Particle Imaging Velocimetry Technique (PIV). Experiments were carried out for three different height ratios in the water channel: h/D = 0, 0.5 and 1. The height ratio is defined as the ratio of the cavity height (between the bottom surface of the circular cylinder and the wall surface). The distance between consecutively placed cylinders was defined as the G/D gap ratio, and it was kept constant throughout the experiments as G/D = 1. Depending on the cylinder diameter, D is determined as the Reynolds number, ReD = 2100, and the thickness of the boundary layer is δ/D = 0.4. Experimental results were evaluated by taking into account time-averaged streamlines <ψ>, time-averaged vortex contour lines, <ω>, and Reynolds stresses, . The findings showed that the gap ratio, G/D and height ratio, h/D have a significant impact on the flow structures around cylinders. As can be seen from the flow data obtained from the experiment, it has been observed that the separation point on the cylinder and the dead flow zone behind the cylinder vary at different cylinder heights. In addition, it was determined that the vortex sizes, <ω>, and Reynolds shear stress, , values formed in the dead flow region differ depending on the cylinder height. It has been determined that the flow around a pair of cylinders has a more complex, unstable, and highly variable structure than that of a single cylinder.