船舶与海洋工程英语阅读：船舶设计师
船舶与海洋工程英语阅读：船舶设计师
The Naval Architect 船舶设计师
A naval architect asked to design a ship may receive his instructions in a form ranging from such simple requirements as “an oil tanker to carry 100 000 tons deadweight at 15 knots” to a fully detailed specification of precily planned requirements. He is usually required to prepare a design for a vesl that must carry a certain weight of cargo (or number of pasngers ) at a specified speed with particular reference to trade requirement; high-density cargoes, such as machinery, require little hold capacity, while the rever is true for low-density cargoes, such as grain.
Deadweight is defined as weight of cargo plus fuel and consumable stores, and lightweight as the weight of the hull, including machinery and equipment. The designer must choo dimensions such that the displacement of the vesl is equal to the sum of the
眼睛的形容词dead weight and the lightweight tonnages. The fineness of the hull must be appropriate to the speed. The draft------which is governed by freeboard rules------enables the depth to be determined to a first approximation.
After lecting tentative values of length, breadth, depth, draft, and displacement, the designer must achieve a weight balance. He must also lect a moment balance becau centres of gravity in both longitudinal and vertical directions must provide satisfactory trim and stability. Additionally, he must estimate the shaft horpower required for the specified speed; this determines the weight of machinery. The strength of the hull must be adequate for the rvice intended, detailed scantlings (frame dimensions and plate thickness ) can be obtained from the rules of the classification society. The scantings determine the requisite weight of hull steel.
The vesl should posss satisfactory steering characteristics, freedom from troublesome vibration, and should comply with the many varied requirements of international regulations. Posssing an attractive appearance, the ship should have the
minimum net register tonnage, the factor on which harbour and other dues are bad. (The gross tonnage reprents the volume of all clod-in spaces above the inner bottom. The net tonnage is the gross tonnage minus certain deductible spaces that do not produce revenue. Net tonnage can therefore be regarded as a measure of the earning capacity of the ship, hence its u as a basis for harbour and docking charges. ) Pasnger vesls must satisfy a standard of bulkhead subdivision that will ensure adequate stability under specified conditions if the hull is pierced accidentally or through collision.
Compromi plays a considerable part in producing a satisfactory design. A naval architect must be a master of approximations. If the required design cloly rembles that of a ship already built for which full information is available, the designer can calculate the effects of differences between this ship and the projected ship. If, however, this information is not available, he must first produce coefficients bad upon experience and, after refining them, check the results by calculation.
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There are four major requirements for a good naval architect. The first is a clear understanding of the fundamental principles of applied science, particularly tho aspects of science that have direct application to ships------mathematics, physics, mechanics, fluid mechanics, materials, structural strength, stability, resistance, and propulsion. The cond is a detailed knowledge of past and prent practice in shipbuilding. The third is personal experience of accepted methods in the design, construction, and operation of ships; and the fourth, and perhaps most important, is an aptitude for tackling new technical problems and of devising practical solutions.
The professional training of naval architects differs widely in the various maritime countries. Unimany universities and polytechnic schools; such academic training must be supplemented by practical experience in a shipyard.
中国第二大城市 Trends in design
镇静的近义词>北半球>常备军 The introduction of calculating machines and computers has facilitated the complex calculations required in naval architecture and has also introduced new concepts in desig
n. There are many combinations of length, breadth, and draft that will give a required displacement. Electronic computers make it possible to prepare ries of designs for a vesl to operate in a particular rvice and to asss the economic returns to the shipowner for each parate design. Such a procedure is best carried out as a joint exerci by owner and builder. As ships increa in size and cost, such combined technical and economic studies can be expected to become more common.
(From “Encyclopedia Britannica”, Vol. 16, 1980)
