Submerged floating tunnel (SFT) is a relatively new infrastructure designed for deep-water crossing. It is generally deeply submerged to reduce large wave loads and facilitate ship traffic. Also, most of the proposed tunnel designs are a cylindrical shape to reduce dynamic motion and mooring tension. For these reasons, the roles of radiation damping and second-order sum- and difference-frequency wave loads are generally marginal, and thus the semi-empirical Morison equation has widely been employed for wave load estimations by many researchers. However, the Morison equation has a limitation as a wavelength is relatively short compared with the characteristic length (i.e., tunnel diameter). &nbsp;In this regard, a time-domain hydro-elastic model is suggested to solve the tunnel-mooring interaction under random wave excitation. The frequency-domain model is initially devised with the discrete-modulus-beam method in which the elastic tunnel is designed with multiple rigid bodies connected by high-order beam elements. The multi-body hydrodynamic coefficients and loads are estimated by potential-theory-based 3D diffraction/radiation program with the coupling stiffness matrix based on the theory of Euler-Bernoulli beam and Saint-Venant torsion. The time-domain hydro-elasticity model is then developed with multi-body Cummins equation and high-order beam elements.Lateral/vertical displacements, mooring tensions, and bending and torsional moments are systematically analyzed under different submergence depth. The Morison-formula-based model is also modeled for comparison. The results show that for SFT with the shallow submergence depth, added mass and radiation damping influence the motion trend while similar time-series motions between two models are observed for the deeply submerged tunnel.

Coupled Time-Domain Hydro-Elastic Simulation for Submerged Floating_x000B_Tunnel Under Wave Excitations

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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