International Shipbuilding Progress - Volume 47, issue 452

Authors: Tao, Z. | Incecik, A.

Article Type: Research Article

Abstract: In this paper, the prediction of nonlinear heave and pitch motions and global bending moments of a ship hull in regular head seas are described. The small amplitude linear theory as well as a large amplitude nonlinear prediction method are used to predict the ship motions in the frequency and time domains. The global bending moment values are predicted utilising two different methods. The first method is based on the elastic vibratory response …due to the total hydrodynamic force and the second method is based on the rigid body response due to linear force superimposed on the elastic response due to impact forces. A series of measurements of ship motions and global bending moments was carried out with a container ship model at different wave frequencies, wave amplitudes and forward speeds. Theoretical prediction results are compared with the experimental data and there is a good agreement between them. Show more

Citation: International Shipbuilding Progress, vol. 47, no. 452, pp. 353-378, 2000

Authors: Wang, D.J. | Bakountouzis, L. | Katory, M.

Article Type: Research Article

Abstract: Ship steering and manoeuvring is described by a system of simultaneous equations of motion in the horizontal plane. Applying a Taylor expansion to the equations of motion produces a linear form in terms of displacement, velocity and acceleration of the ship. Research in this area revolves around the determination of the coefficients in the equations, which are usually referred to as hydrodynamic derivatives. Different methods used by different authors, to estimate these derivatives are briefly highlighted. …The 3D Green's function is then adopted in a boundary integral equation method to calculate the hydrodynamic derivatives for a large tanker and a Mariner class vessel. The velocity-dependent hydrodynamic derivatives are also calculated, using the method developed by Clarke, which is based on regression analysis of experimental data. The calculations are made for both open shallow and restricted waters. The calculations are compared with published experimental results, and the comparison is shown to be, in general, good. It is concluded that estimation of the various hydrodynamic derivatives by analytical means is possible and, accordingly, reliable prediction of ship steering and manoeuvring can be made in the early stages of ship design. Show more

Citation: International Shipbuilding Progress, vol. 47, no. 452, pp. 379-396, 2000

Authors: Chen, Gung-Rong | Fang, Ming-Chung

Article Type: Research Article

Abstract: In the paper, a three-dimensional potential-flow theory is adopted to analyze the diffraction problem between two moving ships in waves. The hydrodynamic interactions between two ships including the speed effect are considered. Basically the general formulations are based on the source distribution technique, by which each ship hull surface is regarded as the assembly of many panels. Using the series expansions of Telste & Noblesse algorithm for the Cauchy principal value integral of unsteady flow, the …corresponding Green functions and their derivatives can be easily solved numerically. Two pairs of models are used for calculations, and comparisons with experimental data and strip theory are made. The hydrodynamic interactions are found to be important generally. But it is also found that the hydrodynamic interaction calculated by 3D method is not so significant as that by 2D method in the resonance region, which is physically reasonable and improves the predictions. The present study offers an efficient tool, which is not very complicated but more reliable, to predict the exciting forces between two moving ships and can be taken as a good basis to analyze the problems of underway replenishment at sea. Show more

Citation: International Shipbuilding Progress, vol. 47, no. 452, pp. 397-420, 2000