Coupled dynamic analysis for wave action on a tension leg-type submerged floating tunnel in time domain

A full time-domain two-dimensional (2-D) numerical model was established for the coupled dynamic analysis of submerged floating tunnel (SFT) structures. For hydrodynamic loads, a second-order time-domain potential flow numerical model was developed and a higher-order boundary element method (HOBEM) was applied to discretize the body boundary and the free surface boundary. The elastic rod theory was used to analyse the cable force to the SFT. Hinged boundary conditions were used at the junction of the mooring line and the structure. The viscous damping coefficient of the submerged cylinder was obtained through a decay physical model test, which was employed in the numerical simulation. In the coupled dynamic analysis, the motion equation for the hull and dynamic equations for the mooring lines were solved simultaneously using the Newmark-β method. The coupled analysis numerical model was applied in an SFT simulation with waves of different frequencies. The influences of viscous damping, buoyancy weight ratios (BWRs), and mooring stiffness distributions on the first- and second-order motion responses and tension of the mooring lines are analysed in detail, and some significant conclusions are presented. •A second-order coupled numerical model is developed to investigate the wave-SFT-mooring system under wave action in time domain.•A decay test is conducted to calculate the viscous damping coefficient of the submerged cylinder, which is employed in the numerical simulation.•The viscous damping weakens the resonance effect induced by the natural frequency of the structure.•The BWR has a great influence on the tension of the mooring system, and a smaller BWR is recommended here.•In the investigation of mooring stiffness effect on the motion response, the stiffness of the inclined anchor chain is recommended to be larger than that of the vertical one.