Lattice Boltzmann method based investigation of flow regime transitions and aerodynamic force modulation in tandem square cylinders with oscillatory inflow

In this study, the fluid flow dynamics is analyzed around two tandem square cylinders through the lattice Boltzmann method at Reynolds number ( Re = 150). Both the non-oscillatory and oscillatory incoming flow environments (with excitation frequency ( f s ) ranging between 0 and 6) are taken into account at the gap spacing values g* = 1, 3.5, 6. Three distinct flow regimes appeared in the analysis include the solitary body flow with a constant drag and steady periodic lift; the symmetric reattaching flow in which the lift amplitude goes increasing with time; and the antiphase vortex shedding flow exhibiting preiodicty in time depdent drag and lift coefficients. The mean drag coefficient of the first cylinder fluctuated between 1.1958 and 1.2645, whereas the downstream cylinder varied from −0.2251 to 0.3654 for the investigated gap spacing and oscillation frequencies. In the symmetric reattaching flow cases, the drag on the second cylinder was found to be negative, indicating strong suction within the gap. The generation of recirculating eddies in the wake is determined to be a response to the excitation frequencies. Their shape, size, and generation mechanisms varied significantly with changing inflow frequencies, even at the same gap ratios. The St as well as the spectrum energy was found to be much influenced by the f s . This study also indicates that, in general, fluctuations in the drag and lift forces are enhanced by oscillations in the incoming flow.