Modelling and analysis of long floating hose string at different working states during the pumping ashore process

Abstract

ABSTRACT During the pumping ashore process, a long floating hose string connects with the shoreline and the other end either free-floating or linking a Trailing Suction Hopper Dredger (TSHD), which suffered both motions of the TSHD and itself under the wind, wave and currents. It is necessary to evaluate the dynamics of the floating hose string to ensure its reliability because their deformation in waves matter the inside slurry flow transportation and may suffer unexpected damaged during the operation and even cause the project delay. Although the composite structure of the dredging hoses can refer to the floating hoses in offshore oil transportation, the bending stiffness, long-distance behaviour and coupling with the motions of the ship and the hose string bring new challenges for modelling and solving. In order to solve the problems, in this study, a numerical model of kilometres-long floating hose string with mechanical properties of the composite hose materials is established with single hose segment bending test data, macro model with lumped mass theory, dynamics of the hose string and coupling analysis with the ship motions. The dynamic performance of kilometres-long floating hoses during the free-floating state and connected TSHD for pumping state with different angles of wind, current, and wave are investigated. The analyses indicate that axial tensions and bending moments of the first 100 m and last 200 m of floating hose string should be noticed, and the amplitude of the tensions remain low and relatively stable when the 60° incoming wave to the ship, which is a better choice in practical operation. Finally, the effects of different sea conditions and lengths of hose string are carried out. The nonlinear geometry and forces of different lengths’ floating hoses during the pumping ashore process were obtained for practical operation reference. Results can help to evaluate long-distance floating hose motions under different sea conditions and provide practical operation suggestions for the working process.