On energy transfer in flow around a row of transversely oscillating square cylinders at low Reynolds number

In this paper, the effects of cylinder spacing, cylinder oscillation frequency, amplitude of cylinder oscillations and Reynolds number on the ensuing flow regimes and energy transition for flow across a row of transversely oscillating cylinders have been studied numerically using the lattice Boltzmann method. The lift and drag coefficient signals are analyzed in detail for finding the extent of lock-on regime and wake interaction mechanism at different spacings. It is noticed that the magnitude of the mean drag coefficient is large at small spacings, which is consistent with a strong wake interaction at small spacings. The effect of wake interaction can also be noticed from the non-monotonic variation of rms lift. The average energy transfer per cylinder oscillation cycle is large when the cylinders oscillate with a frequency near to the natural vortex shedding frequency. The direction of energy transfer changes between positive and negative values with small changes in the cylinder oscillation frequency, suggesting that the direction of energy transfer is very sensitive to this parameter. It is shown that the instantaneous lift coefficient and the cylinder velocity govern the energy transfer from or to the fluid. While the different parameters affect the flow regimes, the cylinder oscillation frequency primarily governs the energy transfer.