Wake interaction studies of flow past tandem circular cylinders for different diameter and gap ratios

Three-dimensional computations are carried out to study the flow past tandem stationary cylinders at moderate Reynolds number (Re = 2,000). Wake structures are analysed with the help of instantaneous vorticity contours and hydrodynamic characteristics are reported using drag and lift coefficient plots. Effects of diameter ratio and gap ratio on wake structure as well as its dynamic characteristics are presented. Cross recurrence analysis is performed to study the coupled interactions between cylinder wakes. In particular, conditions for the in-phase synchronisation, out-of-phase coupling or non-synchronous coupling of the wakes behind the tandem cylinders are identified. Qualitative results obtained from cross recurrence plots are quantified using parameters such as recurrence rate, determinism and averaged diagonal length. These results give deep insight into wake synchronisations between the cylinders. In-phase or out-of-phase wake oscillations can lead to catastrophic structural failures and predicting such conditions can be a useful design tool.