Vortex-induced vibration of curved cables: Asymmetric dynamic and hydrodynamic responses

Vortex-induced vibrations of curved cables are investigated through fully three-dimensional large eddy simulation coupled with a nonlinear beam element method. Four structural axis configurations are considered: concave and convex curved axes with identical curvature, a straight axis, and a low-curvature, nearly straight axis, enabling a systematic comparison of the dynamic and hydrodynamic characteristics between curved and straight-axis structures. The results show that the concave and convex curved configurations exhibit asymmetric raindrop-shaped trajectories with opposite rotational directions, whereas the straight and low-curvature configurations exhibit symmetric crescent and asymmetric crescent trajectories, respectively. The asymmetry of the trajectories is associated with the first-harmonic in-line response induced by the coupling between in-line and cross-flow vibrations. For the curved configurations, a raindrop-shaped motion trajectory, a nonzero mean lift coefficient, and an asymmetric vortex shedding mode appear simultaneously, with the mean lift acting in the direction opposite to the structural bending. Furthermore, it is confirmed that the curved configuration primarily affects the spanwise distribution of the hydrodynamic coefficients and the wake vorticity field, whereas the asymmetric motion trajectory is the key factor leading to a nonzero mean lift coefficient and an asymmetric vortex shedding mode. These findings advance the fundamental understanding of VIV mechanisms in curved configurations and provide a scientific basis for the design and operation of suspended structures, such as submarine cables.