Ship model basin
Encyclopedia
- a physical basinDock (maritime)A dock is a human-made structure or group of structures involved in the handling of boats or ships, usually on or close to a shore.However, the exact meaning varies among different variants of the English language...
or tankWater tankA Water tank is a container for storing water. The need for a water tank is as old as civilized man, providing storage of water for drinking water, irrigation agriculture, fire suppression, agricultural farming, both for plants and livestock, chemical manufacturing, food preparation as well as many...
used to carry out hydrodynamic tests with ship modelShip modelShip models or model ships are scale representations of ships. They can range in size from 1/6000 scale wargaming miniatures to large vessels capable of holding people....
s, for the purpose of designing a new (full sized) ship, or refining the design of a ship to improve the ship's performance at sea;
- the organization (often a company) that owns and operates such a facility.
In the second meaning, the company or authority is an engineering firm.
that acts as a contractor to the relevant shipyard
Shipyard
Shipyards and dockyards are places which repair and build ships. These can be yachts, military vessels, cruise liners or other cargo or passenger ships. Dockyards are sometimes more associated with maintenance and basing activities than shipyards, which are sometimes associated more with initial...
s, and provides hydrodynamic model tests
and numerical calculations to support the design and development of ships and offshore structures.
The hydrodynamic test facilities present at a model basin site include at least:
- A towing tank: This is a basin, several metres wide and hundreds of metres long, equipped with a towing carriage that runs on two rails on either side. The towing carriage can either tow the model or follow the self-propelled model, and is equipped with computers and devices to register or control, respectively, variables such as speed, propeller thrust and torque, rudder angle etc. The towing tank serves for resistance and propulsion tests with towed and self-propelled ship models to determine how much power the engine will have to provide to achieve the speed laid down in the contract between shipyard and ship owner. The towing tank also serves to determine the maneuvering behaviour in model scale. For this, the self-propelled model is exposed to a series of zig-zag maneuvers at different rudder angle amplitudes. Post-processing of the test data by means of system identificationSystem identificationIn control engineering, the field of system identification uses statistical methods to build mathematical models of dynamical systems from measured data...
results in a numerical model to simulate any other maneuver like Dieudonné spiral test or turning circles. Additionally, a towing tank can be equipped with a PMM (planar motion mechanism) or a CPMC (computerized planar motion carriage) to measure the hydrodynamic forces and moments on ships or submerged objects under the influence of oblique inflow and enforced motions. The towing tank can also be equipped with a wave generator to carry out seakeeping tests, either by simulating natural (irregular) waves or by exposing the model to a wave packet that yields a set of statistics known as response amplitude operatorResponse amplitude operatorIn the field of ship design and design of other floating structures, a response amplitude operator is an engineering statistic, or set of such statistics, that are used to determine the likely behaviour of a ship when operating at sea...
s (acronym RAO), that determine the ship's likely real-life sea-going behavior when operating in seas with varying wave amplitudes and frequencies (these parameters being known as sea stateSea stateIn oceanography, a sea state is the general condition of the free surface on a large body of water—with respect to wind waves and swell—at a certain location and moment. A sea state is characterized by statistics, including the wave height, period, and power spectrum. The sea state varies with...
s). Modern seakeeping test facilities can determine these RAO statistics, with the aid of appropriate computer hardware and software, in a single test.
- A cavitation tunnel to investigate propellerPropellerA propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...
s. This is a vertical water circuit with large diameter pipes. At the top, it carries the measuring facilities. A parallel inflow is established. With or without a ship model, the propeller, attached to a dynamometerDynamometerA dynamometer or "dyno" for short, is a device for measuring force, moment of force , or power. For example, the power produced by an engine, motor or other rotating prime mover can be calculated by simultaneously measuring torque and rotational speed .A dynamometer can also be used to determine...
, is brought into the inflow, and its thrust and torque is measured at different ratios of propeller speed (number of revolutions) to inflow velocity. A stroboscopeStroboscopeA stroboscope, also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. The principle is used for the study of rotating, reciprocating, oscillating or vibrating objects...
synchronized with the propeller speed serves to visualize cavitation as if the cavitation bubble would not move. By this, one can observe if the propeller would be damaged by cavitation. To ensure similarity to the full-scale propeller, the pressure is lowered, and the gas content of the water is controlled.
- Workshops: Ship model basins manufacture their ship models from wood or paraffinParaffinIn chemistry, paraffin is a term that can be used synonymously with "alkane", indicating hydrocarbons with the general formula CnH2n+2. Paraffin wax refers to a mixture of alkanes that falls within the 20 ≤ n ≤ 40 range; they are found in the solid state at room temperature and begin to enter the...
with a computerized milling machineMilling machineA milling machine is a machine tool used to machine solid materials. Milling machines are often classed in two basic forms, horizontal and vertical, which refers to the orientation of the main spindle. Both types range in size from small, bench-mounted devices to room-sized machines...
. Some of them also manufacture their model propellers. Equipping the ship models with all drives and gauges and manufacturing equipment for non-standard model tests are the main tasks of the workshops.
Some ship model basins have further facilities, for example:
- A maneuvering and seakeepingSeakeepingSeakeeping ability is a measure of how well-suited a watercraft is to conditions when underway. A ship or boat which has good seakeeping ability is said to be very seaworthy and is able to operate effectively even in high sea states....
basin. This is a test facility that is wide enough to investigate arbitrary angles between waves and the ship model, and to perform maneuvers like turning circles, for which the towing tank is too narrow. However, some important maneuvers like the spiral test still require even more space and still have to be simulated numerically after system identification.
- An Ice TankIce TankAn ice tank is a ship model basin whose purpose is to provide a physical modeling environment for the interaction of ship, structures, or sea floor with both ice and water. Ice tanks may take the form of either a towing tank or maneuvering basin....
: To develop ice breaking vesselsIcebreakerAn icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters. Although the term usually refers to ice-breaking ships, it may also refer to smaller vessels .For a ship to be considered an icebreaker, it requires three traits most...
, this tank fulfills similar purposes as the towing tank does for open water vessels. Resistance and required engine power as well as maneuvering behaviour are determined depending on the ice thickness. Also ice forces on offshore structures can be determined. Ice layers are frozen with a special procedure to scale down the ice crystals to model scale. Also tests in brash ice are performed.
Additionally, these companies or authorities have CFD
Computational fluid dynamics
Computational fluid dynamics, usually abbreviated as CFD, is a branch of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows. Computers are used to perform the calculations required to simulate the interaction of liquids and gases with...
software and experience to simulate the complicated flow around ships and their rudders and propellers numerically. Today's state of the art does not yet allow software to replace model tests in their entirety by CFD calculations. One reason, but not the only one, is that elementization is still expensive. Also the lines design of some of the ships is carried out by the specialists of the ship model basin, either from the beginning or by optimizing the initial design obtained from the shipyard. The same applies to the design of propellers.
The ship model basins worldwide are organized in the ITTC http://ittc.sname.org/ (International Towing Tank Conference) to standardize their model test procedures.
Some of the most significant ship model basins are the David Taylor Model Basin
David Taylor Model Basin
The David Taylor Model Basin is one of the largest ship model basins — test facilities for the development of ship design — in the world...
and the Davidson Laboratory http://www.stevens.edu/ses/cms/Facilities/index.html at Stevens Institute of Technology
Stevens Institute of Technology
Stevens Institute of Technology is a technological university located on a campus in Hoboken, New Jersey, USA – founded in 1870 with an 1868 bequest from Edwin A. Stevens. It is known for its engineering, science, and technological management curricula.The institute has produced leading...
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, The High Speed Towing Tank facility at Naval Science and Technological Labs at Vizag India, The Institute for Ocean Technology http://iot-ito.nrc-cnrc.gc.ca/about_e.html in St. Johns, Canada, FORCE Technology http://forcetechnology.com in Lyngby, Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
, SSPA
SSPA
-See also:*Block upconverter *Orthomode transducer *Signal-to-noise ratio*Bias tee*Duo LNB*Low noise amplifier *Transmit and receive integrated assembly...
, http://www.sspa.se in Gothenburg, Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
, the Maritime Research Institute Netherlands (MARIN)
MARIN (research)
MARIN, the Maritime Research Institute Netherlands, is one of the leading institutes in the world for hydrodynamic research and maritime technology. The services incorporate a unique combination of simulation, model testing, full-scale measurements and training programmes. MARIN provides services...
http://www.marin.nl in Wageningen, the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
, the INSEAN in Rome
Rome
Rome is the capital of Italy and the country's largest and most populated city and comune, with over 2.7 million residents in . The city is located in the central-western portion of the Italian Peninsula, on the Tiber River within the Lazio region of Italy.Rome's history spans two and a half...
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, the SVA Potsdam http://www.sva-potsdam.de in Potsdam
Potsdam
Potsdam is the capital city of the German federal state of Brandenburg and part of the Berlin/Brandenburg Metropolitan Region. It is situated on the River Havel, southwest of Berlin city centre....
, the HSVA http://www.hsva.de in Hamburg
Hamburg
-History:The first historic name for the city was, according to Claudius Ptolemy's reports, Treva.But the city takes its modern name, Hamburg, from the first permanent building on the site, a castle whose construction was ordered by the Emperor Charlemagne in AD 808...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, the "Bassin d'essai des carènes" in Val de Reuil http://www.bassin.fr, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
and CEHIPAR http://www.cehipar.es in Madrid, Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
, CTO S.A. http://www.cto.gda.pl/en in Gdansk, Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
External Links
- "Putting More Speed And Power In Our Navy" , June 1943, Popular Science large and well illustrated article on towing basins