Phase jump and energy transfer of forced oscillating circular cylinder in uniform flow

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Phase jump and energy transfer of forced oscillating circular cylinder in uniform flow

Tang, Guoqiang / Lu, Lin / Zhao, Ming / Liu, Mingming / Zong, Zhi

The phase jump, energy transfer, and the associated vortex shedding modes of a circular cylinder undergoing forced oscillation normal to the incoming uniform flow are investigated numerically at Reynolds number (Re) of 200. The dependence of the fluid forces on the non-dimensional oscillating amplitude A* = A/D ∈ [0.1, 0.6] and frequency f* = f_e/f_s ∈ [0.5, 2.0] is examined, where A is the oscillating amplitude, D is the cylinder diameter, f_e is the cylinder oscillating frequency, and f_s is the Strouhal frequency of fixed cylinder at the same Reynolds number, respectively. The lock-in region is identified by the combination of Fourier analysis and Lissajous phase diagram. The phase difference between displacement and lift fluctuation and the energy transfer between fluid and structure are discussed. Within the lock-in region, a jump in the phase difference is found to occur in the cases with A* = 0.5 and 0.55 without a wake mode transition. The numerical results reveal that the appearance of the phase jump is consistent with the reversal of the energy transfer direction. For the special cases of A* = 0.5 and 0.55, changes in the sign of energy transfer are observed, while no reversal of energy transfer is observed at other amplitudes. The energy transfer direction is either from fluid to cylinder when A* ∈ [0.1, 0.4] or from cylinder to fluid when A* ≥ 0.6. It is confirmed that the energy transfer between fluid and cylinder is not only dependent on cylinder oscillating frequency but also on cylinder oscillating amplitude.