Numerical Simulation On Hydrodynamic Response Of Berthing Ships

The motion of ships berthed in front of wharfs affect structure and wharf stability, so it is important to study the hydrodynamic response of berthing ships. Simulation of ship motion in berthing condition is not a simple problem. The present researches on ship berthing are mostly carried out by experimental methods. In this paper, a time domain method is developed to solve the differential equation of the ship motion based on the linear 3-D potential theory. The hydrodynamic response of berthing ships in open sea pillar quay and vertical docks are studied respectively. The ultimate conclusion provide theoretical basis and project reference.First of all, the wave exciting force, added mass and radiation damping are computed by means of a high order boundary element method in the frequency domain. The numerical method is adopted to calculate the radiation of a uniform cylinder in front of a vertical wall and truncated cylinder in open sea. The results compare with the analytical results to examine the numerical method.Secondly, the impulse functions are obtained by the Fourier transform of the radiation damping in time domain analysis. The differential equation of ship motion is computed by the four-order Runge-Kutta integrating method in the time domain. In the model, the ship surface geometry is fitted by using B-Spline functions and computing meshes are generated on ship hulls automatically. The stress-strain relationships of mooring cables and fenders are also fitted by using B-Spline functions.Thirdly, the radiation damping which is computed by the linear diffraction/radiation is not adequate for the ship motions of a long floating structure. For ships, barges and similar long offshore structures, the nonlinear viscous damping effects on the bodies. In view of this situation, some researches are made on nonlinear viscous damping in this thesis.Finally, comparisons are made between the present numerical results and experimental results, which were carried out in the laboratory. The good agreement between the present numerical results and experimental test results proves the validity of the mathematical model presented in this paper.