Abstract

By employing the lattice-Boltzmann method (LBM) with respect to Bhatnagar–Gross–Krook (BGK) collision model, a 2-D computational study is performed to investigate the flow structures, force coefficients and vortex-shedding characteristics behind a single-square cylinder and two side-by-side cylinders at different spacing conditions (1.0 ⩽ T/D ⩽ 4.5). The flow patterns around the square cylinders are determined using the contour plot. Significant observations from this study are as follows: (a) a flip flop regime is observed for T/D = 1.0, whereas a wiggling/Flutter shielding pattern is observed at T/D = 3.5 and a synchronized flow pattern is observed for the spacing ratio of T/D = 4.5, (b) the frequencies observed for the smaller spacing ratios (T/D = 1.0, 3.5) having numerous peaks in the spectra. Subsequently the frequencies were observed at T/D = 4.5 having a single dominating peak frequency, (c) the main motivation for the significant variation in flow patterns is due to the changes in mean drag coefficients, root mean square values of the aerodynamic coefficients and Strouhal number, (d) it is observed that the formation of vortex strongly depends on the spacing ratios between the cylinders. From the results, it is identified that the cylinders at higher spacing ratios (T/D = 4.5) produce minimum oscillation when compared to the smaller spacing ratios.