Numerical Simulation of Vortex-Induced Vibrations of Inclined Cables under Different Wind Profiles

Vortex-induced vibration of an inclined cable under wind with varying velocity profiles was investigated through computational fluid dynamics numerical simulation. As a complicated fluid-structure interaction issue, the flow field around the freely oscillating cable was simulated byAnsys CFX 11.0, and the cable oscillation as calculated using the Galerkin approach (realized by the additional subroutine, which is embedded into Ansys CFX 11.0). The shear stress transport k-omega turbulent model based on the Reynolds-averaged Navier-Stokes method was employed to simulate the behavior of turbulent flow in the CFD numerical simulation. The above computational method and turbulent model were validated through comparison of the computational results with the wind tunnel test results of a rigid circular cylinder. And then, two inclination angles, 30 degrees and 90 degrees, were chosen for the inclined cable; wind with a uniform velocity profile (velocity profile U) and four types of velocity profiles were used as the inlet velocity conditions. Based on the cable vibration and flow field obtained under wind with varying velocity profiles, characteristics of the cable vibrations and aerodynamic coefficients in the time domain and frequency domain as well as the wake patterns were analyzed. The results indicated that the cable vibration exhibits two types of behavior-single-mode vibration (uniform wind or the wind with small velocity changes) and multimode vibration (the wind with large velocity changes)-according to the velocity profile over the inclined cable. The single-mode vibration of the cable exhibited a standing wave response (a chessboard pattern), whereas the multimode vibration exhibited a traveling wave motion (a parallel line pattern). The lift coefficients exhibited similar features as the cable vibration under wind with varying velocity profiles. Dominant frequencies of the lift coefficients could be observed over the upper segments of the cable under wind with small velocity changes (or the entire cable length under uniform wind), but a broader frequency band appeared in the lift coefficients over the low segments of the cable under wind with large velocity changes. The wake patterns and vortex shedding lock-in regions depended on the vibration type (or the wind velocity profiles). The single-mode vibration had large lock-in regions (the entire cable length or the upper segments of the cable), and over these regions, the vortex shedding was in phase or synchronous. However, for a multimode vibration (wind with large velocity changes), the vortex shedding is irregular and complicated along the cable axis. DOI: 10.1061/(ASCE)BE.1943-5592.0000323. (C) 2013 American Society of Civil Engineers.