Discrete-Module-Beam-Based Hydro-Elasticity Simulations for Moored Submerged Floating Tunnel under Regular and Random Wave Excitations

Abstract

This study investigates the hydro-elastic behaviors of a moored submerged floating tunnel (SFT) using a fully-coupled time-domain hydro-elastic model based on the discrete-module-beam (DMB) method. In frequency domain, multibody hydrodynamic coefficients and wave excitation forces are obtained from 3D potential theory. In the time-domain DMB-based hydro-elastic model, the multibody Cummins equation and coupled stiffness matrix according to the theory of Euler-Bernoulli beam and Saint-Venant torsion are used. Mooring lines are modeled with rod theory and high-order finite-element formulations. The tunnel is then coupled with mooring lines by linear springs at respective connection locations. The present DMB model is validated through comparisons with two independent commercial programs, i.e., quasi-static computation based on the 3D solid model by ABAQUS and dynamic simulation using the semi-empirical Morison model by OrcaFlex. Then, the effects of various design parameters, such as submergence depths, buoyancy-weight ratios (BWRs), and wave conditions, on dynamic responses and mooring tensions are evaluated. The effects of nonlinear snap loadings and first- and second-order wave forces on SFT dynamics in regular and random waves are also investigated. Wet natural frequencies and mode shapes, hydro-elastic lateral and vertical displacements, mooring tensions, and bending moments for various cases are presented and analyzed.