We often observe that our body feels lighter while taking a swim in the pool. Also, when drawing water from a well, the bucket feels lighter till it is partially or fully immersed in water. Have you ever wondered why this change in weight is felt?
We can say, when immersed in water or any other fluid, the body experiences a force from the downward direction opposite to the direction of the gravitational pull, which is responsible for the decrease in its weight. It can be the reason why a ball of plastic floats in water rather than sinking to the base by its weight. But here too, we observe that some objects such as a plastic bottle float over water, while others such as a needle sink. In this article, we shall learn about the concept of buoyancy and buoyant force which gives a proper explanation of such observations.
Buoyancy is the force that causes objects to float. It is the force exerted on an object that is partly or wholly immersed in a fluid. Buoyancy is caused by the differences in pressure acting on opposite sides of an object immersed in a static fluid. It is also known as the buoyant force. Buoyancy is the phenomena due to Buoyant Force.
Using propulsion forces, ships are able to manoeuvre themselves in the water. Initially while there were limited number of ship propulsion systems, in the present era there are several innovative ones with which a vessel can be fitted with. Today ship propulsion is not just about successful movement of the ship in the water. It also includes using the best mode of propulsion to ensure a better safety standard for the marine ecosystem along with cost efficiency.
1. Diesel Propulsion
Diesel propulsion system is the most commonly used marine propulsion system converting mechanical energy from thermal forces. Diesel propulsion systems are mainly used in almost all types of vessels along with small boats and recreational vessels.
2. Wind Propulsion
Wind propulsion emerged as an alternative to those systems which emit huge quantities of CO2 gases in the marine atmosphere. However, the usage of wind turbine marine propulsion has not started extensively in large commercial ships because of a requirement of constant windiness. Two wind propulsion systems for ships that have become lately are- kite propulsion and sail propulsion for merchant ships.
3. Nuclear Propulsion
Naval vessels incorporate the usage of nuclear maritime propulsion. Using the nuclear fission process, nuclear propulsion is a highly complex system consisting of water reactors and other equipment to fuel the vessel. The nuclear reactors in the ships are also used to generate electricity for the ship. Several merchant ships are also being planned to be constructed with this propulsion system
4. Gas Turbine Propulsion
Gas turbine propulsion is used for naval as well as non-naval ships. In case of naval ships, the gas turbine propulsion system aids in faster movement of the ships which is necessary in case of the ship coming under attack.
5. Fuel Cell Propulsion
Fuel cell propulsion systems use hydrogen as the main fuel component. Electricity is created in the fuel cell without any combustion whatsoever. The process is clean and therefore has been regarded as a very important alternative marine propulsion system. There are various types of propulsion under the fuel cell propulsion head like PEM (Photon-Exchange-Membrane) and the molten-carbonate systems.
6. Biodiesel Fuel Propulsion
Biodiesel propulsion has been deemed as a potential marine propulsion system for the future. Currently tests are being carried out to find out about the viability of this propulsion system which is expected to be in full operation by the year 2017.
7. Solar Propulsion
Solar propulsion for ships was utilized for the first time in the year 2008. Solar propulsion benefits include a high reduction in the poisonous carbon dioxide emissions. Solar propulsions are capable of generating a capacitance as high as 40 kilowatts (kW).
8. Steam Turbine Propulsion
Steam turbine propulsion involves the usage of coal or other steam-generating fuels to propel the vessel. Steam turbine maritime propulsion system was highly utilized between the late 19th and the early 20th century.
9. Diesel-Electric Propulsion
In simple terms, diesel-electric ship propulsion systems use a combination of a generator operated by electricity attached to a diesel motor. The technology has been in use since the early 1900s. In today’s times, submarines and merchant ships incorporate the diesel-electric propulsion system to propel themselves.
10. Water-Jet Propulsion
Water-jet propulsion has been used since the year 1954. The most important advantage of water-jet propulsion is that it does not cause noise pollution and offers a high speed to the vessels. In contrast the water-jet propulsion as a ship propulsion system is costlier to maintain which can cause problems to the user.
11. Gas fuel or Tri Fuel Propulsion
LNG fuel is now utilized to be burnt in the Main Engine after adopting some modification in the propulsion engine to reduce emission from the ship. It is known as tri fuel because it can burn gas fuel, diesel and heavy fuel.
The various types of propulsion systems offer their own unique advantages to a vessel. Depending on the necessity and the requirement, the best type of ship propulsion system needs to be fitted. Only then the vessel will be able to offer its optimum service capacitance.
Originally smaller, jumboisation made Seawise Giant the largest ship ever by length, displacement (657,019 tonnes), and deadweight tonnage. The largest and longest ships ever to be laid down per original plans.
The world’s longest ships are listed according to their overall length (LOA), which is the maximum length of the vessel measured between the extreme points in fore and aft. In addition, the ships’ deadweight tonnage (DWT) and/or gross tonnage (GT) are presented as they are often used to describe the size of a vessel.
The ships are listed by type. Only ship types for which there exist a ship longer than 300 metres (1,000 ft) are included. For each type, the list includes current record-holders either as individual ships, ship classes or standard designs, up to four runner-ups, and all longer ships that have been scrapped. The list does not include non-self-propelled floating structures such as such as the 488 m (1,601 ft) long Prelude FLNG.
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