Vortex-induced vibration of double cylinders under different tandem spacing

To investigate the vortex-induced vibration displacement response, force characteristics, and vibration trajectories of double cylinders under different tandem spacing and reduced velocities, a coupled simulation of computational fluid dynamics and computational structural dynamics was carried out in this present study. Unsteady Reynolds-Averaged Navier–Stokes equations were solved using a coupling algorithm, while the structural vibration equations were solved using the fourth-order Runge–Kutta method. The fourth-order Runge–Kutta algorithm was implemented in Fluent through user-defined function. By comparing with the experimental data, the accuracy of the numerical model was verified. The research results show that in terms of frequency response, the change of tandem spacing leads to the alteration of the lock-in regions of the upstream and downstream cylinders with a certain hysteresis, and the lock-in region of the downstream cylinder is enlarged. The lift coefficient of the downstream cylinder decreases with the increase in tandem spacing. Regarding the vibration trajectories, the trajectory of the upstream cylinder gradually exhibits regularity with the increase in spacing, while the trajectory of the downstream cylinder is diverse due to interference. The frequency and power spectral density curves exhibit complex variations, influenced comprehensively by spacing and reduced velocity. These variations follow distinct trends with changes in reduced velocity under different spacings, offering critical data and a robust theoretical foundation for engineering applications and academic research.