The characteristics of flows past a circular cylinder with heat transfer in the proximity to the wall at different gap ratios

In this study, two-dimensional laminar flows past a circular cylinder under isothermal and non-isothermal conditions over a flat-plate were investigated numerically at Re = 200. The gap ratio G/D ranges from 0.5 to 3.0, with G representing the distance between the lower surface of the cylinder and the wall. The effects of G/D on the flow dynamics were explored. For G/D=0.5, the vortex shedding of the lower cylinder surface is suppressed and there is a large recirculation region on the wall. For G/D=1.0, the recirculation region is small and the lower vortex begins to shed. For G/D⩾1.5, the flow exhibits similarities to that of an unbounded cylinder. The heat transfer characteristics was evaluated. When the cylinder temperature Tc is higher than the air temperature Ta, the mean drag coefficient CD¯ is reduced and the root-mean-square lift coefficient CL′ is increased. The temperature field is reconstructed using the proper orthogonal decomposition method, which is influenced by the large-scale vortical structures.