Naval engineering

Steamer New York in c. 1908

Naval architecture is an engineering discipline dealing with the design, construction and repair of marine vehicles. Naval architecture involves basic and applied research, design, development, design evaluation and calculations during all stages of the life of a marine vehicle. Preliminary design of the vessel, its detailed design, construction, trials, operation and maintenance, launching and dry-docking are the main activities involved. Ship design calculations are also required for ships being modified(by means of conversion, rebuilding, modernization, or repair). Formulation of safety regulations and damage control rules and the approval and certification of ship designs to meet such statutory and non-statutory requirements are also included in naval architecture.

Contents

Overview

Due to the complexity associated with operating in a marine environment naval architecture is a co-operative effort between groups of technically skilled individuals who are specialists in particular fields, often coordinated by a lead naval architect.1 This inherent complexity also means that the analytical tools available are much less evolved than those for designing aircraft, cars and even space craft. This is due primarily to the paucity of data on the environment the marine vehicle is required to work in and the complexity of the interaction of waves and wind on a marine structure.

Elements

The word "vessel" includes every description of water craft, including non-displacement craft, WIG craft and seaplanes, used or capable of being used as a means of transportation on water.2 The principle elements of naval architecture are:3

  • Hydrostatics
This is the study of conditions under which the vessel is subjected to while at rest in water and its ability to remain afloat. This involves computing buoyancy, (displacement) and other hydrostatic properties.
Trim - refers to the longitudinal inclination of the vessel.
Stability - Ability of a vessel to restore itself to an upright position after being inclined by wind, sea, or conditions of loading.
Concerns the flow of water around the ship hull and over bodies such as propeller blades or rudder, or through thruster tunnels.
Resistance - resistance towards motion in water primarily caused due to flow of water around the hull. Powering calculation is done based on this.
Propulsion - to move the vessel through water using propellers, thrusters, water jets, sails etc. The energy to drive these is mainly provided by internal combustion engines. Some vessels are electrically powered using nuclear or solar energy.
Ship motions - involves motions of the vessel in seaway and its responses in waves.
Controllability (manoeuvring) - involves controlling and maintaining position and direction of the vessel
Involves selection of material of construction, structural analysis of global and local strength of the vessel, vibration of the structural components and structural responses of the vessel during motions in seaway.
  • Arrangements
This involves concept design, layout and access, fire protection, allocation of spaces and capacity.
Construction depends on the material used. When steel or aluminium is used this involves welding of the plates and profiles after rolling, marking, cutting and bending as per the structural design drawings or models, followed by erection and launching. Other joining techniques are used for other materials like fibre reinforced plastic and glass reinforced plastic.

The craft of naval architecture

Venetian gondola

Traditionally, naval architecture has been more craft than science. The suitability of a vessel's shape was judged by looking at a half-model of a vessel or a prototype. Ungainly shapes or abrupt transitions were frowned on as being flawed. This included, rigging, deck arrangements, and even fixtures. Subjective descriptors such as ungainly, full, and fine were used as a substitute for the more precise terms used today. A vessel was, and still is described as having a ‘fair’ shape. The term ‘fair’ is meant to denote not only a smooth transition from fore to aft but also a shape that was ‘right.’ Determining what is ‘right’ in a particular situation in the absence of definitive supporting analysis encompasses the art of naval architecture to this day.

The science of naval architecture

Hull Form

Modern low-cost digital computers and dedicated software, combined with extensive research to correlate full-scale, towing tank and analytical data, have enabled naval architects to more accurately predict the performance of a marine vehicle. These tools are used for static stability (intact and damaged), dynamic stability, resistance, powering, hull development, structural analysis, etc. Data is regularly shared in international conferences sponsored by RINA, Society of Naval Architects and Marine Engineers (SNAME) and others. Computational Fluid Dynamics is being applied to predict the response of a floating body in a random sea.

The Naval Architect

A naval architect is an engineer who is responsible for the design, construction, and/or repair of ships, boats, other marine vessels, and offshore structures, both commercial and military, including:

Some of these vessels are amongst the largest and most complex and highly valued movable structures produced by mankind. They are the most efficient method of transporting the world's raw materials and products known to man. Modern engineering on this scale is essentially a team activity conducted by specialists in their respective fields and disciplines. Naval architects integrate these activities. This demanding leadership role requires managerial qualities and the ability to bring together the often-conflicting demands of the various design constraints to produce a product which is fit for the purpose.4

In addition to this leadership role, a naval architect also has a specialist function in ensuring that a safe, economic, and seaworthy design is produced. To undertake all these tasks, a naval architect must have an understanding of many branches of engineering and must be in the forefront of high technology areas. He or she must be able to effectively utilize the services provided by scientists, lawyers, accountants, and business people of many kinds.

Naval architects typically work for shipyards, ship owners, design firms and consultancies, equipment manufacturers, regulatory bodies, navies, and governments.

See also

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References

  1. ^ American Society of Naval Engineers. Naval engineering brochure.
  2. ^ Convention On The International Regulations for Preventing Collisions at Sea, 1972,As Amended; International Maritime Organization; ISBN 92-801-4167-8
  3. ^ Lewis V, Edward (Ed.); (June 1989). Principles of Naval Architecture (2nd Rev.) Vol. 1 - Society of Naval Architects and Marine Engineers. ISBN 09-397-7300-7
  4. ^ "Position Classification Standard for Naval Architecture Series, GS-0871, U.S. Office of Personnel Management".

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  • This page was last modified on 18 November 2008, at 02:23.

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