Lock-in phenomenon in the wake flow past an oscillating circular nano-cylinder

Abstract

In this paper, the lock-in/synchronization phenomenon in the wake flow around an oscillating nano-cylinder is studied with molecular dynamics simulation. The results show that the lock-in valley of the velocity fluctuation also occurs in nano-scale. Similar to those in normal scales (usually >1 mm), three regimes of lock-in, transition, and no-lock-in states are also obtained. Unlike in normal scales, the concurrence of the density and velocity fluctuation waves with different phase and the same frequency makes the fluctuation frequency of the lift force different from that of the velocity. The oscillation of the nano-cylinder can intensify the lift force fluctuation, especially in the lock-in state. The intensity of the lift force increases with the amplitude of the nano-cylinder vibration. The lock-in valley of the lift force usually covers a wider range of frequency than that of the velocity. Improving the inflow Reynolds number can reduce the coverage range of the lock-in valley in frequency. The lock-in valley does not vary apparently as the Jz number, which represents the interaction intensity between fluid molecules, increases until it approaches Jz ≈ 1.4. The rise of Kn number can promote the occurrence of the lock-in phenomenon.