Numerical simulation of flow around a transversely oscillating square cylinder at different frequencies

This study employed the k–ω Shear StressTransport turbulence model and the Arbitrary Lagrangian–Eulerian dynamic mesh method in OpenFOAM to investigate the effects of the oscillation frequency ratio (fr) on flow characteristics around a square cylinder at Re = 2.2 × 104. The results revealed that the time-averaged drag coefficient (Cd¯) and the Root Mean Square (RMS) of the lift coefficient (Cl′) reached the peak values when fr = 1.0. For fr ≥ 2.5, the time-averaged pressure coefficient (Cp¯) on the leeward side of the square cylinder exhibited a distribution pattern characterized by higher values in the middle and lower values near the edges, while the RMS of the pressure coefficient (Cp′) demonstrated the opposite trend. As fr increased, the secondary recirculation bubbles along the sidewalls of the square cylinder gradually diminished, while the primary recirculation bubbles in the wake and near the sidewalls shortened. Additionally, the RMS of the transverse velocity (Uy′) exceeded that of the streamwise velocity (Ux′) in the wake region. The energy transfer coefficient (CE) in the synchronous range was significantly lower than that in the non-synchronous range at different fr. It is worth noting that in the synchronous range, the energy transferred from the cylinder to the fluid attained its maximum value. The amplitude spectrum of the lift coefficient exhibited chaotic characteristics, containing exclusively odd-order superharmonics. With increasing fr, the vortex structures on both sides of the cylinder became increasingly fragmented, and the wake's vortex pattern transitioned from a single-row to a double-row structure. These findings provide a deeper theoretical understanding of turbulence and the flow-induced motion of structures.