Numerical investigation of wake modes for flow past three tandem cylinders using the multi-relaxation-time lattice Boltzmann method for different gap spacings

In this paper, the effect of gap spacing on the flow past three square cylinders in tandem arrangement is studied numerically using a 2-D multi-relaxation-time lattice Boltzmann method (MRT-LBM). The Reynolds number is fixed at 75 and variation of the gap spacing is from 0.5 to 17. The results are compared to some earlier published results and found to be in good agreement. Five different wake modes are observed by the increment in the gap spacing. To understand the effect of different gap spacings on the flow-induced forces; a detailed analysis of mean drag coefficient, time signal analysis of drag and lift coefficients, Strouhal number, root mean square values of drag and lift coefficients is presented in this article. In this study, it is observed that the critical gap spacing is 3, its existence and effects on the flow characteristics are also studied.