Fluid-structure interaction simulation and optical fibre stress analysis of submarine cables in vortex-induced vibration

Under the current scouring, submarine cables are prone to be exposed, suspended, and even vortex-induced vibration (VIV), threatening their mechanical and electrical properties. In this contribution, a finite element simulation model of 110-kV single-core optical fibre composite submarine cable is established. The natural frequency and resonant frequency of the model are obtained through wet mode analysis and harmonic response analysis. Then the VIV is simulated by the fluid-structure coupling method. Moreover, the stress extraction method of the torsional optical fibre position under the VIV is proposed. The results show that when the reduced speed is 2.57, the submarine cable appears beating vibration, which is composed of two vibrations with similar frequencies. When the reduced speed is 7.08, the vibration frequency is about 7.813 Hz, causing a rapid increase in vibration amplitude. The stress distribution of the torsional optical fibre presents a mirror image relationship at two moments separated by half a vibration cycle. Also, the frequency of stress change is the same as the frequency of VIV, which can judge whether the VIV occurs. The VIV range and position can be determined by the location where the stress changes the most. Fluid-structure interaction modelling approach of submarine cable and vortex-induced vibration simulations for suspended submarine cable.Comprehensive analysis of the resonance phenomena and stress analysis method for the torsional optical fibre. image