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3500t油船性能设计外文翻译

更新时间:2014-11-29:  来源:毕业论文
3500t油船性能设计外文翻译
按照物理支撑方式而划分的船舶类型。 
就船舶分类而言,物理支撑形式是基本于船舶在设计情况下进行的假定。船舶设计成在水上、水面或者水下
工作,因此气—水交界面将用于参考数据。因为前面提到的三个区域的物理环境特性差异很大,设计成在这些区域工作的船舶的物理特性也不同。  空气静力支撑:有两种类型船舶是靠前身产生的空气垫而支撑在海面之上的。这些相对较轻的船舶具有很高的航速,因为空气阻力远小于水阻力,还有的原因是在告诉航行时不与海浪接触以及采用的柔性密封连接减少了海浪的冲击。这类船舶依靠鼓风机在船底部形成一个低压空气垫。这个空气垫必须足以支撑起水上船舶的重量。第一种类型船的四周具有柔性的“裙”,在船底围成一个空气垫,试船能完全升离水面。另外一种是具有刚性侧壁或薄壳的气垫型船,侧壁伸到水面下,维持气垫压力所需的空气流量就降低了。  水动力支撑:依靠水动力支撑的船也只有两种类型。水动力是靠专门设计的水动力板在水面下具有快速相对运动而产生的。物理学原理表明任何带来不对称流体的运动物体都会在垂直于运动的方向上产生一个升力。正像具有机翼的飞机在空气中运动能产生升力一样,通过一个穿过水面的支柱而固定在水下的木翼,其水动力可以支撑一般船舶离开水面。  静水力支撑:是最古老的也是最可靠地支撑类型——静水力支撑。静水力支撑通常称为浮力,可以由公元前二世纪古代哲学及数学家阿基米德发现的物理定律来解释。阿基米德定律指出,浸没在液体中的物体将受到一个等一所排开的液体重量的浮力作用。这一定律适用于浮在水面或在下潜到水中的任何船。水包括海水和淡水。依据这一定律,这类船可以统称为排水型船。  最常见的是排水型船一般分类为通用海洋运输船,它们可以用作客运、轻货运输、拖网捕鱼或各种不需要特殊舱容、速度、吃水、或其它特殊性能的其他业务。这类船最常见并很容易识别,具有适度的排水量、航速、长度和舱容。它们通常具有最大的航程和最好的适航性,属于“全季节船”,是所有其它排水型船分类时重要参照的标准。
在这种标准船型中,最重要的船型是散装油船,油船和其它超级油船,它们不仅在世界贸易中也在全球工业中扮演重要角色。这些船属于排水型船,具有巨大的浮力支撑。当满载时其船体在水下有非常巨大的和不成比例的体积。事实上,货物重量远远超过船本身的重量。一艘满载的VLCC的吃水或要求的水深在50~60英尺之间,一艘ULCC大概要80英尺。这些船舶在排水型船舶中有专用的类型称为深排水量船。另外还有一类排水型船具有大的吃水。类似于前面讨论过的原油船,但吃水还没有 超过它们。这类船称为SWATH(小水线面双体船)。简单地讲,这类极少见的船型设计成在中等程度海况中具有高速和稳定性的上体(上部结构)。它们的未来是有疑问的,但在水面以下提供大多数排水体积,通过窄的立柱支撑水面以上的船体或甲板的理论是完善的,通过上层平台而连接在一起的双船体提供了必要的稳性。   http://www.lwfree.cn The performance designing of 3500t oil tanker  Ships Typed According to Means of Physical Support.  The mode of physical support by which vessels can be categorized assumes that the vessel is operating under designed conditions. Ships are designed to operate above, on, or below the surface of the sea, so the air-sea interface will be used as the reference datum. Because the nature of the physical environment is quite different for the three regions just mentioned, the physical characteristics of ships designed to operate in those regions can be diverse.  Aerostatic Support:There are two categories of vessels that are supported above the surface of the sea on a self-induced cushion of air. These relatively lightweight vehicles are capable of high speeds, since air resistance is considerably less than water resistance, and the absence of contact with small waves combined with flexible seals reduces the effects of wave impact at high speed. Such vessels depend on lift fans to create a cushion of low-pressure air in an underbody chamber. This cushion of air must be sufficient to support the weight of the vehicle above the water surface.The first type of vessel has flexible “skirts” that entirely surround the air cushion and enable the ship to rise completely above the sea surface.The other type of air-cushion
craft has rigid side walls or thin hulls that extend below the surface of the water to reduce the amount of air flow required to maintain the cushion pressure.  Hydrodynamic Support:There are also two types of vessels that depend on dynamic support generated by relatively rapid forward motion of specially designed hydrodynamic shapes either on or beneath the surface of the water. A principle of physics states that any moving object that can produce an unsymmetrical flow pattern generates a lift force perpendicular to the direction of motion. Just as an airplane with (airfoil) produces lift when moving through the air, a hydrofoil, located beneath the surface and attached by means of a surface piercing strut, can dynamically support a vessel’s hull above the water.  Hydrostatic Support:there is the oldest and most reliable type of support, hydrostatic support.This hydrostatic support, commonly recognized as flotation, can be explained by a fundamental physical law that the ancient philosopher-mathematician Archimedes defined in the second century B.C. Archimedes’ Principle states that a body immersed in a liquid is buoyed up (or acted upon) by a force equal to the weight of the liquid displaced. The most ubiquitous type of displacement ship can be generally classified as the common carrier, a seagoing vessel. It may be employed for passenger service, light cargo-carrying, fishing by trawling or for hundreds of other tasks that do not require exceptional capacity, speed, submergence, or other special performance. It is the most common and easily recognizable type of ship, with moderate displacement, moderate speeds, moderate to large lengths, and moderate capacities. It usually embodies the maximum in cruising range and seaworthiness. It is the “ship for all seasons.” It is the standard to which all other ship classifications in the displacement category may be referred.  The closest relative to this standard vessel, which plays a crucial role not only in world commerce but in the survival of the industrial world as well, is the bulk, oil carrier, the tanker, or supertanker. These terminologies are common but unspecific, and in this discussion they are inadequate, for whatwas called a supertanker several years ago is today not a supertanker.Such vessels belong to a category of displacement ship that has a great range of buoyant support. They have a very large and disproportionate hull volume below the surface when fully loaded. Indeed, the cargo weight far exceeds the weight of the ship itself. The draft or depth of water required for a fully loaded VLCC runs to 50 or 60 feet and the ULCC may be 80 feet. Such ships belong in the exclusive category of displacement vessels called deep displacement ships.There exists another type of displacement hull with extreme draft. However, it is similarity to the crude-oil carrier of the preceding discussion goes no further than that. This type of vessel is called the SWATH( small waterplane area twin hull). Briefly, this rather rare breed of ship is designed for relatively high speed and stable platform in moderately rough water. Its future is problematical, but the theory of placing the bulk of the displacement well below the surface and extending the support to the above-water platform or deck through the narrow waterline fins or struts is sound. Twin hulls connected by an upper platform provide the necessary operating stability.
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