International Shipbuilding Progress

This paper summarizes an investigation on the suitability of mathematical surfaces for representing an idealized curved hull surface. In contrast to hull fairing with splines, mathematical surfaces such as the Gordon or Coons surfaces can be further developed. A study for candidate mathematical surfaces is made to examine how well they represent a benchmark hull surface. The results indicate that the UNO and Gordon surfaces are more accurate. The use of geodesic traces for hull plate development and an integrated hull plate development procedure are also discussed.

Time-honoured ancient Xizhang Junk form remains to be predominant in the barge train fleet which plays an important role in domestic transport of the Jiangnan region crisscrossed by waterways in East China.

With a view to reduce the formation coefficient of barge train, the shallow water resistance of the Xizhang Junk, both individually and in train, has been investigated both by means of towing tank model tests and full-scale trials in Grand Canal. A modified body plan is proposed. Operational results have shown good energy-saving, if the modified form barge is placed as the first one in the barge train. In the appendix, empirical formulae based on existing vessels are given to show the parametric features of Xizhang Junk form.

This paper presents the results of a study on a tuned liquid damper (TLD). The TLD uses air and liquid inside a U-shape tank as the mass of dynamic damper of a structure. By using the Lagrange method, the dynamic equation of motion for the fluid inside the structure with this U-shape tuned liquid damper is derived.

The natural frequency of the U-shape TLD is determined by finding the peak value of displacements of the liquid versus exciting accelerations. Vibration behaviours of the structure with and without U-shape TLD subjected to a simple harmonic excitation are examined in the time domain. Effects of mass ratio (mass of U-shape TLD/mass of structure) on vibration reduction are also studied.

The circulation control method for improving the hydrodynamic characteristics of a low aspect ratio rudder is investigated in circulating water-channel tests. Circulation control is achieved from a thin jet of water that exits through a 0.45mm spanwise slot along the upper surface of the airfoil near the trailing edge. Experimental investigations have demonstrated that the lift increases as the jet blowing increases, and the lift augmentation is obtained even at zero deg angle of attack with relatively small amounts of blowing water. Endplates installed at both ends of rudder's span are shown to increase the lift at fixed angle of attack and decrease the drag. The longitudinal V grooves engraved at Coanda surface are also shown to decreases the drag and improve the lift-to-drag ratio.

In the paper, the analyses of the stability and resultant wave profile for a ship advancing in oblique waves are made. A time simulation technique based on the previously well developed strip theory is used to calculate the ship motion and the relative wave elevation along the ship. An Instant Grid-Generation (IGG) technique is also applied to reduce the laborious work for the input preparation. The resultant wave elevation includes not only the incident wave but also the diffraction and radiation waves. To analyze the ship stability in waves, the instantaneous wave profile along the ship is derived. The wave profile prediction is also improved by using a more accurate estimation between the incident wave and hull side. The related hydrodynamic coefficients are treated in the manner of large ship motion, hence it is a nonlinear problem. From the present analysis, it is found that the ship stability in waves indeed differs from that in calm water. The authors regard that the present technique can offer more general ship stability analysis and will be helpful to understand the ship capsizing behavior in waves.