This study thoroughly examines the onset of vortex shedding and flow regimes of flow past two side-by-side square cylinders. The Reynolds number (Re) and the separation ratio (g) are varied from 10 to 200 and 0.5 to 5, respectively. The method of investigation is the single-relaxation-time lattice Boltzmann method. Meaningful changes in physical parameters, such as mean drag coefficients and Strouhal numbers, are found for both cylinders as the values of Reynolds numbers and separation ratio change. The onset of vortex shedding is found for each selected separation ratio while changing the value of the Reynolds number from 10 to 200. It was found that the onset of vortex shedding occurred at different Reynolds numbers as the value of the separation ratio increased from 0.5 to 5. Changing the value of the Reynolds number for all g values, we have also observed the flow undergo significant pattern changes due to the onset of recirculation and the subsequent change from a steady to an unsteady periodic nature. A distinct combination of occurrences for dominating frequencies in terms of the primary vortex shedding frequency and secondary cylinder interaction frequencies in the flow can effectively identify different flow regimes. The unsteady periodicity in the flow changes from a non-sinusoidal periodic nature at (Re, g) = (1.5, 140) (flip-flopping flow) to a weakly interactive flow regime at (Re, g) = (3.0, 140), according to the time-variant lift plots. For a better understanding of the proposed problem, this study will give power spectra, force statistics, time-trace analysis of forces, and visualization of instantaneous vorticity contours.
Naqeeb et al. (Fri,) studied this question.