Naval Architecture

To build ships for foreign customers is obviously more complicated than for domestic shipowners. First of all, it will involve the problem of language, not to mention all the possible complicated procedures involved in the foreign trade. All the documents shall be written in English language, including email,faxes, memos, letter of intent ( intention), contracts and so on.

Propeller root cavitation problems can be among the most complex to solve. In this region, along with tip vortex dynamics, rigorous mathematical analysis is currently of little assistance for design or analysis purposes. In some cases, when scant attention has been paid to the propeller design environment or where ship layout difficulties have arisen and high shaft angles or a poor choice of advance angle have resulted, erosion problems can occur which are difficult to resolve.

One such case is that of a fast displacement craft where deep cavitation erosion in the blade root regions was produced after only 30 minutes running at full power.The problem was identified as originating in the angle of attack variations at the blade roots due to the propeller shaft’s inclination.

3. Finite difference methods (FDM)

FDM discretize (like FEM) the whole fluid domain. The derivatives in the field equations are approximated by finite differences. Discretization errors can lead to a violation of conservation of mass or momentum, i.e. in the course of a simulation the amount of water might diminish continously.

CFD comprises methods that solve the basic field equations subject to boundary conditions by approaches involving a large number of (mathematically simple) elements. These approaches lead automatically to a large number of unknowns. Basic CFD techniques are:

1. Boundary element methods (BEM)

BEM are used for potential flows. For potential flows, the integrals over the whole fluid domain can be transformed to integrals over the boundaries of the fluid domain.

A. Part of the Test List During the Sea Trial (Continued)

16. test of exhaust gas economizer evaporation

17. test of fresh water generator

18. main engine remote control test

In the meantime, the shipyard may begin to prepare for all the documents for the delivery of the vessel. Among the documents are the Protocol of Trials of the vessel, Protocol of Inventory of the equipment of the vessel including spare parts and the like, Protocol of Stores of Consumable Nature, Finished Drawings and

Plans pertaining to the Vessel, Protocol of Deadweight and Inclining Experiment and all certificates required to be furnished upon the delivery of the vessel. When all the defects have been remedied or repaired, the ship is ready for delivery.

The trial run of an ocean-going vessel is usually referred to as the sea trial, for the vessel shall undertake the overall performance test at sea.

According to the shipbuilding practice the representatives from the ship-owner and the classification society shall be present on board during the sea trial. The ship builder shall bear all the expenses in connection with the trial run of the vessel.

In addition, the builder shall also prepare necessary ballast ( fresh water and sea water and such other ballast as may be required) to bring the vessel to the trial load draft.

The increasing demand for quality management and clearly documented procedures, preferably on an international standard, led to the formation of various panels of experts. The Japan Marine Standards Association submitted in 1998 a proposal for an ISO standard for the assessment of speed and power in speed trials.

Trial tests of the built ship are an important prerequisite for the acceptance of the ship by the shipowner and are always specified in the contract between shipowner and shipyard. The problem is that the trial conditions differ from both model test conditions and design conditions.

In our shipyards, a lot of modern computers have been introduced and a computer network for the whole corporation with a connection to the Internet has been established. The speed and quality for design and manufacture are thus guaranteed, and considerable benefits and profits have been achieved through computer application.