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Ship Resistance And Propulsion
A ship must be designed to move efficiently through the water with a minimum of external force. For thousands of years ship designers and builders of sailing vessels used rules of thumb based on the midship-section area to size the sails for a given vessel. The hull form and sail plan for the clipper ships, for example, evolved from experience, not from theory. It was not until the advent of steam power and the construction of large iron ships in the mid-19th century that it became clear to ship owners and builders that a more rigorous approach was needed. Definition Ship resistance is defined as the force required to tow the ship in calm water at a constant velocity. Components of resistance A body in water which is stationary with respect to water, experiences only hydrostatic pressure. Hydrostatic pressure always acts to oppose the weight of the body. The total (upward) force due to this buoyancy is equal to the (downward) weight of the displaced water. If the body is in moti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ship
A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished from boats, based on size, shape, load capacity, and purpose. Ships have supported exploration, trade, warfare, migration, colonization, and science. After the 15th century, new crops that had come from and to the Americas via the European seafarers significantly contributed to world population growth. Ship transport is responsible for the largest portion of world commerce. The word ''ship'' has meant, depending on the era and the context, either just a large vessel or specifically a ship-rigged sailing ship with three or more masts, each of which is square-rigged. As of 2016, there were more than 49,000 merchant ships, totaling almost 1.8 billion dead weight tons. Of these 28% were oil tankers, 43% were bulk carriers, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Waterline Length
A vessel's length at the waterline (abbreviated to L.W.L)Note: originally Load Waterline Length is the length of a ship or boat at the level where it sits in the water (the ''waterline''). The LWL will be shorter than the length of the boat overall (''length overall'' or LOA) as most boats have bows and stern protrusions that make the LOA greater than the LWL. As a ship becomes more loaded, it will sit lower in the water and its ambient waterline length may change; but the registered L.W.L it is measured from a default load condition. This measure is significant in determining several of a vessel's properties, such as how much water it displaces, where the bow and stern waves occur, hull speed, amount of bottom-paint needed, etc. Traditionally, a stripe called the "boot top" is painted around the hull just above the waterline. In sailing boats, longer waterline length will usually enable a greater maximum speed, because it allows greater sail area, without increasing beam or d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kite
A kite is a tethered heavier-than-air or lighter-than-air craft with wing surfaces that react against the air to create lift and drag forces. A kite consists of wings, tethers and anchors. Kites often have a bridle and tail to guide the face of the kite so the wind can lift it. Some kite designs don’t need a bridle; box kites can have a single attachment point. A kite may have fixed or moving anchors that can balance the kite. The name is derived from kite, the hovering bird of prey. The lift that sustains the kite in flight is generated when air moves around the kite's surface, producing low pressure above and high pressure below the wings. The interaction with the wind also generates horizontal drag along the direction of the wind. The resultant force vector from the lift and drag force components is opposed by the tension of one or more of the lines or tethers to which the kite is attached. The anchor point of the kite line may be static or moving (e.g., the towin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sail
A sail is a tensile structure—which is made from fabric or other membrane materials—that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails may be made from a combination of woven materials—including canvas or polyester cloth, laminated membranes or bonded filaments—usually in a three- or four-sided shape. A sail provides propulsive force via a combination of lift and drag, depending on its angle of attack—its angle with respect to the apparent wind. Apparent wind is the air velocity experienced on the moving craft and is the combined effect of the true wind velocity with the velocity of the sailing craft. Angle of attack is often constrained by the sailing craft's orientation to the wind or point of sail. On points of sail where it is possible to align the leading edge of the sail with the apparent wind, the sail may act as an airfoil, generating propulsive force as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horse-drawn Boat
A horse-drawn boat or tow-boat is a historic boat operating on a canal, pulled by a horse walking beside the canal on a towpath. United Kingdom The Romans are known to have used mules to haul boats on their waterways in the UK. Boat horses were the prime movers of the Industrial Revolution, and they remained at work until the middle of the 20th century. A horse, towing a boat with a rope from the towpath, could pull fifty times as much cargo as it could pull in a cart or wagon on roads. In the early days of the Canal Age, from about 1740, all boats and barges were towed by horse, mule, hinny, pony or sometimes a pair of donkeys. Many of the surviving buildings and structures had been designed with horse power in mind. Horse-drawn boats were used well into the 1960s on UK canals for commercial transport, and are still used today by passenger trip boats and other pleasure traffic. The Horseboating Society has the primary aims of preserving and promoting Horseboating on the canals ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human-powered Watercraft
Human-powered watercraft are watercraft propelled by human power. The three main methods of collecting human power are directly from the hands or feet, through the hands with oars, paddles, or poles, or through the feet with pedals and a crank or treadle. While most human-powered watercraft use buoyancy to maintain their position relative to the surface of the water, a few, such as human-powered hydrofoils and human-powered submarines, use hydrofoils, either alone or in addition to buoyancy. Oared craft Oars are held at one end, have a blade on the other end, and pivot in between in oarlocks. Oared craft include: * Racing shell Using oars in pairs, with one hand on each oar, is two-oar sculling. The oars may also be called sculls. Two-oared sculled craft include: * Adirondack guideboat * Banks dory, Gloucester dory, and McKenzie River dory * Dinghy * Sampans rowed by foot in Ninh Bình Province of northern Vietnam. * Scull, Single scull, Double scull, Quad scull, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Propulsion
Marine propulsion is the mechanism or system used to generate thrust to move a watercraft through water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of an electric motor or internal combustion engine driving a propeller, or less frequently, in pump-jets, an impeller. Marine engineering is the discipline concerned with the engineering design process of marine propulsion systems. Human-powered paddles and oars, and later, sails were the first forms of marine propulsion. Rowed galleys, some equipped with sail, played an important early role in early human seafaring and warfares. The first advanced mechanical means of marine propulsion was the marine steam engine, introduced in the early 19th century. During the 20th century it was replaced by two-stroke or four-stroke diesel engines, outboard motors, and gas turbine engines on faster ships. Marine nuclear reactors, which appeared in the 195 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat and light. Energy is a conserved quantity—the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The unit of measurement for energy in the International System of Units (SI) is the joule (J). Common forms of energy include the kinetic energy of a moving object, the potential energy stored by an object (for instance due to its position in a field), the elastic energy stored in a solid object, chemical energy associated with chemical reactions, the radiant energy carried by electromagnetic radiation, and the internal energy contained within a thermodynamic system. All living organisms constantly take in and release energy. Due to mass–energy equivalence, any object th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Thomson, 1st Baron Kelvin
William Thomson, 1st Baron Kelvin, (26 June 182417 December 1907) was a British mathematician, Mathematical physics, mathematical physicist and engineer born in Belfast. Professor of Natural Philosophy (Glasgow), Professor of Natural Philosophy at the University of Glasgow for 53 years, he did important work in the mathematical analysis of electricity and formulation of the first and second laws of thermodynamics, and did much to unify the emerging discipline of physics in its contemporary form. He received the Royal Society's Copley Medal in 1883, was its President of the Royal Society, president 1890–1895, and in 1892 was the first British scientist to be elevated to the House of Lords. Absolute temperatures are stated in units of kelvin in his honour. While the existence of a coldest possible temperature (absolute zero) was known prior to his work, Kelvin is known for determining its correct value as approximately −273.15 degrees Celsius or −459.67 degrees Fahrenheit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wake (physics)
In fluid dynamics, a wake may either be: * the region of recirculating flow immediately behind a moving or stationary blunt body, caused by viscosity, which may be accompanied by flow separation and turbulence, or * the wave pattern on the water surface downstream of an object in a flow, or produced by a moving object (e.g. a ship), caused by density differences of the fluids above and below the free surface and gravity (or surface tension). Viscosity The wake is the region of disturbed flow (often turbulent) downstream of a solid body moving through a fluid, caused by the flow of the fluid around the body. For a blunt body in subsonic external flow, for example the Apollo or Orion capsules during descent and landing, the wake is massively separated and behind the body is a reverse flow region where the flow is moving toward the body. This phenomenon is often observed in wind tunnel testing of aircraft, and is especially important when parachute systems are involved, becau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wave
In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (resting) value at some frequency. When the entire waveform moves in one direction, it is said to be a ''traveling wave''; by contrast, a pair of superimposed periodic waves traveling in opposite directions makes a ''standing wave''. In a standing wave, the amplitude of vibration has nulls at some positions where the wave amplitude appears smaller or even zero. Waves are often described by a ''wave equation'' (standing wave field of two opposite waves) or a one-way wave equation for single wave propagation in a defined direction. Two types of waves are most commonly studied in classical physics. In a '' mechanical wave'', stress and strain fields oscillate about a mechanical equilibrium. A mechanical wave is a local deformation (strain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
