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A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce
lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Paternoster lift, a type of lift using a continuous chain of cars which do not stop ** Patient lift, or Hoyer lift, mobile ...
or
thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
, or provide the ability to steer or stabilize motion while traveling in water, air, or other
fluids In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...
. Fins are also used to increase surface areas for heat transfer purposes, or simply as ornamentation. Fins first evolved on
fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
as a means of locomotion.
Fish fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as see ...
s are used to generate
thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
and control the subsequent motion. Fish, and other aquatic animals such as
cetaceans Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
, actively propel and steer themselves with
pectoral Pectoral may refer to: * The chest region and anything relating to it. * Pectoral cross, a cross worn on the chest * a decorative, usually jeweled version of a gorget * Pectoral (Ancient Egypt), a type of jewelry worn in ancient Egypt * Pectorali ...
and tail fins. As they swim, they use other fins, such as
dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal co ...
and
anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...
s, to achieve stability and refine their maneuvering.Helfman G, Collette BB, Facey DE and Bowen BW (2009
"Functional morphology of locomotion and feeding"
Chapter 8, pp. 101–116. In:''The Diversity of Fishes: Biology'', John Wiley & Sons. .
The fins on the tails of
cetaceans Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
,
ichthyosaurs Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, alt ...
, metriorhynchids,
mosasaurs Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on th ...
, and
plesiosaurs The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared ...
are called flukes.


Generating thrust

Foil shaped fins generate
thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
when moved, the lift of the fin sets water or air in motion and pushes the fin in the opposite direction. Aquatic animals get significant
thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
by moving fins back and forth in water. Often the tail fin is used, but some aquatic animals generate thrust from
pectoral fins Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...
. Fins can also generate thrust if they are rotated in air or water.
Turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating e ...
s and
propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...
s (and sometimes
fans Fan commonly refers to: * Fan (machine), a machine for producing airflow, often used for cooling ** Hand fan, an implement held and waved by hand to move air for cooling * Fan (person), short for fanatic; an enthusiast or supporter, especially wit ...
and
pump A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they u ...
s) use a number of rotating fins, also called foils, wings, arms or blades. Propellers use the fins to translate torquing force to lateral thrust, thus propelling an aircraft or ship. Turbines work in reverse, using the lift of the blades to generate torque and power from moving gases or water.
Cavitation Cavitation is a phenomenon in which the static pressure of a liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, cal ...
can be a problem with high power applications, resulting in damage to propellers or turbines, as well as noise and loss of power.Franc, Jean-Pierre and Michel, Jean-Marie (2004
''Fundamentals of Cavitation''
Springer. .
Cavitation occurs when negative pressure causes bubbles (cavities) to form in a liquid, which then promptly and violently collapse. It can cause significant damage and wear. Cavitation damage can also occur to the tail fins of powerful swimming marine animals, such as dolphins and tuna. Cavitation is more likely to occur near the surface of the ocean, where the ambient water pressure is relatively low. Even if they have the power to swim faster, dolphins may have to restrict their speed because collapsing cavitation bubbles on their tail are too painful. Cavitation also slows tuna, but for a different reason. Unlike dolphins, these fish do not feel the bubbles, because they have bony fins without nerve endings. Nevertheless, they cannot swim faster because the cavitation bubbles create a vapor film around their fins that limits their speed. Lesions have been found on tuna that are consistent with cavitation damage.
Scombrid The mackerel, tuna, and bonito family, Scombridae, includes many of the most important and familiar food fishes. The family consists of 51 species in 15 genera and two subfamilies. All species are in the subfamily Scombrinae, except the butterf ...
fishes (tuna, mackerel and bonito) are particularly high-performance swimmers. Along the margin at the rear of their bodies is a line of small rayless, non-retractable fins, known as
finlet Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as s ...
s. There has been much speculation about the function of these finlets. Research done in 2000 and 2001 by Nauen and Lauder indicated that "the finlets have a hydrodynamic effect on local flow during steady swimming" and that "the most posterior finlet is oriented to redirect flow into the developing tail vortex, which may increase thrust produced by the tail of swimming mackerel". Fish use multiple fins, so it is possible that a given fin can have a hydrodynamic interaction with another fin. In particular, the fins immediately upstream of the caudal (tail) fin may be proximate fins that can directly affect the flow dynamics at the caudal fin. In 2011, researchers using volumetric imaging techniques were able to generate "the first instantaneous three-dimensional views of wake structures as they are produced by freely swimming fishes". They found that "continuous tail beats resulted in the formation of a linked chain of vortex rings" and that "the dorsal and anal fin wakes are rapidly entrained by the caudal fin wake, approximately within the timeframe of a subsequent tail beat".


Controlling motion

Once motion has been established, the motion itself can be controlled with the use of other fins. Boats control direction (yaw) with fin-like rudders, and roll with stabilizer fins and keel fins.Perez, Tristan (2005
''Ship Motion Control: Course Keeping and Roll Stabilisation Using Rudder and Fins''
Springer. .
Airplanes achieve similar results with small specialised fins that change the shape of their wings and tail fins.McClamroch, N Harris (2011
''Steady Aircraft Flight and Performance''
Page 2–3, Princeton University Press. .
Stabilising fins are used as
fletching Fletching is the fin-shaped aerodynamic stabilization device attached on arrows, bolts, darts, or javelins, and are typically made from light semi-flexible materials such as feathers or bark. Each piece of such fin is a fletch, also known as a ...
on
arrow An arrow is a fin-stabilized projectile launched by a bow. A typical arrow usually consists of a long, stiff, straight shaft with a weighty (and usually sharp and pointed) arrowhead attached to the front end, multiple fin-like stabilizers c ...
s and some
darts Darts or dart-throwing is a competitive sport in which two or more players bare-handedly throw small projectile point, sharp-pointed projectile, missiles known as dart (missile), darts at a round shooting target, target known as a #Dartboard, dar ...
, and at the rear of some
bomb A bomb is an explosive weapon that uses the Exothermic process, exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-t ...
s,
missile In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocket i ...
s,
rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...
s, and self-propelled
torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, su ...
es. These are typically
planar Planar is an adjective meaning "relating to a plane (geometry)". Planar may also refer to: Science and technology * Planar (computer graphics), computer graphics pixel information from several bitplanes * Planar (transmission line technologies), ...
and shaped like small wings, although
grid fin Grid fins (or lattice fins) are a type of flight control surface used on rockets and bombs, sometimes in place of more conventional control surfaces, such as planar fins. They were developed in the 1950s by a team led by and used since the 197 ...
s are sometimes used. Static fins have also been used for one satellite,
GOCE ''Goce'' is an opera composed by Kiril Makedonski (1925–1984), written by Venko Markovski and dedicated to Gotse Delchev. The work was commissioned to be the very first opera performed by the Macedonian National Opera Company. It premiered on Ma ...
.


Regulating temperature

Engineering fins are also used as heat transfer fins to regulate temperature in
heat sink A heat sink (also commonly spelled heatsink) is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant, where it is dissipated away from the device, th ...
s or fin radiators.


Ornamentation and other uses

In biology, fins can have an adaptive significance as sexual ornaments. During courtship, the female
cichlid Cichlids are fish from the family Cichlidae in the order Cichliformes. Cichlids were traditionally classed in a suborder, the Labroidei, along with the wrasses ( Labridae), in the order Perciformes, but molecular studies have contradicted this ...
, ''
Pelvicachromis taeniatus ''Pelvicachromis taeniatus'' is a species of cichlid from Benin and Nigeria that is occasionally kept as an aquarium fish. It is native to the soft-water rivers. This species can reach a length of SL. It is known to exist in a variety of geog ...
'', displays a large and visually arresting purple
pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...
. "The researchers found that males clearly preferred females with a larger pelvic fin and that pelvic fins grew in a more disproportionate way than other fins on female fish." Reshaping human feet with
swim fin Swim or SWIM may refer to: Movement and sport * Swim, a fad dance * Aquatic locomotion, the act of biologically propelled motion through a liquid medium * Human swimming, the useful or recreational activity of movement through water * Swimming ...
s, rather like the tail fin of a fish, add thrust and efficiency to the kicks of a
swimmer Swimming is an individual or team racing sport that requires the use of one's entire body to move through water. The sport takes place in pools or open water (e.g., in a sea or lake). Competitive swimming is one of the most popular Olympic ...
or
underwater diver Underwater diving, as a human activity, is the practice of descending below the water's surface to interact with the environment. It is also often referred to as diving (disambiguation), diving, an ambiguous term with several possible meani ...
Surfboard fins provide surfers with means to maneuver and control their boards. Contemporary surfboards often have a centre fin and two cambered side fins. The bodies of
reef fish Coral reef fish are fish which live amongst or in close relation to coral reefs. Coral reefs form complex ecosystems with tremendous biodiversity. Among the myriad inhabitants, the fish stand out as colourful and interesting to watch. Hundreds ...
es are often shaped differently from open water fishes. Open water fishes are usually built for speed, streamlined like torpedoes to minimise friction as they move through the water. Reef fish operate in the relatively confined spaces and complex underwater landscapes of
coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. Co ...
s. For this manoeuvrability is more important than straight line speed, so coral reef fish have developed bodies which optimize their ability to dart and change direction. They outwit predators by dodging into fissures in the reef or playing hide and seek around coral heads. The pectoral and pelvic fins of many reef fish, such as
butterflyfish The butterflyfish are a group of conspicuous tropical marine fish of the family Chaetodontidae; the bannerfish and coralfish are also included in this group. The approximately 129 species in 12 genera are found mostly on the reefs of the Atla ...
,
damselfish Damselfish are those within the subfamilies Abudefdufinae, Chrominae, Lepidozyginae, Pomacentrinae, and Stegastenae within the family Pomacentridae. Most species within this group are relatively small, with the largest species being about 30 ...
and angelfish, have evolved so they can act as brakes and allow complex maneuvers.Ichthyology
''Florida Museum of Natural History''. Retrieved 22 November 2012.
Many reef fish, such as
butterflyfish The butterflyfish are a group of conspicuous tropical marine fish of the family Chaetodontidae; the bannerfish and coralfish are also included in this group. The approximately 129 species in 12 genera are found mostly on the reefs of the Atla ...
,
damselfish Damselfish are those within the subfamilies Abudefdufinae, Chrominae, Lepidozyginae, Pomacentrinae, and Stegastenae within the family Pomacentridae. Most species within this group are relatively small, with the largest species being about 30 ...
and angelfish, have evolved bodies which are deep and laterally compressed like a pancake, and will fit into fissures in rocks. Their pelvic and pectoral fins are designed differently, so they act together with the flattened body to optimise maneuverability. Some fishes, such as
puffer fish Tetraodontidae is a family of primarily marine and estuarine fish of the order Tetraodontiformes. The family includes many familiar species variously called pufferfish, puffers, balloonfish, blowfish, blowies, bubblefish, globefish, swellfish ...
,
filefish The filefish (Monacanthidae) are a diverse family of tropical to subtropical tetraodontiform marine fish, which are also known as foolfish, leatherjackets or shingles. They live in the Atlantic, Pacific and Indian Oceans. Filefish are closely rel ...
and
trunkfish Ostraciidae is a family of squared, bony fish belonging to the order Tetraodontiformes, closely related to the pufferfishes and filefishes. Fish in the family are known variously as boxfishes, cofferfishes, cowfishes and trunkfishes. It contains ...
, rely on pectoral fins for swimming and hardly use tail fins at all.


Evolution of fins

There is an old theory, proposed by anatomist
Karl Gegenbaur Karl Gegenbaur (21 August 1826 – 14 June 1903)"Karl Gegenbaur – Encyclopædia Britannica" (biography), ''Encyclopædia Britannica'', 2006, Britannica.coBritannica-KarlG was a German anatomist and professor who demonstrated that the field of c ...
, which has been often disregarded in science textbooks, "that fins and (later) limbs evolved from the gills of an extinct vertebrate". Gaps in the fossil record had not allowed a definitive conclusion. In 2009, researchers from the University of Chicago found evidence that the "genetic architecture of gills, fins and limbs is the same", and that "the skeleton of any appendage off the body of an animal is probably patterned by the developmental genetic program that we have traced back to formation of gills in sharks". Recent studies support the idea that gill arches and paired fins are serially homologous and thus that fins may have evolved from gill tissues. Fish are the ancestors of all mammals, reptiles, birds and amphibians. In particular, terrestrial
tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct theraps ...
s (four-legged animals) evolved from fish and made their first forays onto land 400 million years ago. They used paired pectoral and pelvic fins for locomotion. The pectoral fins developed into forelegs (arms in the case of humans) and the pelvic fins developed into hind legs. Much of the genetic machinery that builds a walking limb in a tetrapod is already present in the swimming fin of a fish. In 2011, researchers at
Monash University Monash University () is a public research university based in Melbourne, Victoria, Australia. Named for prominent World War I general Sir John Monash, it was founded in 1958 and is the second oldest university in the state. The university has a ...
in Australia used primitive but still living
lungfish Lungfish are freshwater vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, i ...
"to trace the evolution of pelvic fin muscles to find out how the load-bearing hind limbs of the tetrapods evolved." Further research at the University of Chicago found bottom-walking lungfishes had already evolved characteristics of the walking gaits of terrestrial tetrapods. In a classic example of
convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
, the pectoral limbs of
pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to ...
s,
birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
and
bats Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bi ...
further evolved along independent paths into flying wings. Even with flying wings there are many similarities with walking legs, and core aspects of the genetic blueprint of the pectoral fin have been retained. About 200 million years ago the first mammals appeared. A group of these mammals started returning to the sea about 52 million years ago, thus completing a circle. These are the
cetacean Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
s (whales, dolphins and porpoises). Recent DNA analysis suggests that cetaceans evolved from within the
even-toed ungulate The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...
s, and that they share a common ancestor with the
hippopotamus The hippopotamus ( ; : hippopotamuses or hippopotami; ''Hippopotamus amphibius''), also called the hippo, common hippopotamus, or river hippopotamus, is a large semiaquatic mammal native to sub-Saharan Africa. It is one of only two extan ...
. About 23 million years ago another group of bearlike land mammals started returning to the sea. These were the
seals Seals may refer to: * Pinniped, a diverse group of semi-aquatic marine mammals, many of which are commonly called seals, particularly: ** Earless seal, or "true seal" ** Fur seal * Seal (emblem), a device to impress an emblem, used as a means of a ...
. What had become walking limbs in cetaceans and seals evolved further, independently in a reverse form of convergent evolution, back to new forms of swimming fins. The forelimbs became flippers and the hind limbs became a tail terminating in two fins, called a
fluke Fluke may refer to: Biology * Fluke (fish), a species of marine flatfish * Fluke (tail), the lobes of the tail of a cetacean, such as dolphins or whales, ichthyosaurs, mosasaurs Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ...
in the case of cetaceans. Fish tails are usually vertical and move from side to side. Cetacean flukes are horizontal and move up and down, because cetacean spines bend the same way as in other mammals.
Ichthyosaur Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, altho ...
s are ancient reptiles that resembled dolphins. They first appeared about 245 million years ago and disappeared about 90 million years ago.
"This sea-going reptile with terrestrial ancestors converged so strongly on fishes that it actually evolved a
dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...
and tail in just the right place and with just the right hydrological design. These structures are all the more remarkable because they evolved from nothing — the ancestral terrestrial reptile had no hump on its back or blade on its tail to serve as a precursor."Martill D.M. (1993). "Soupy Substrates: A Medium for the Exceptional Preservation of Ichthyosaurs of the Posidonia Shale (Lower Jurassic) of Germany". ''Kaupia – Darmstädter Beiträge zur Naturgeschichte'', 2 : 77–97.
The biologist
Stephen Jay Gould Stephen Jay Gould (; September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. He was one of the most influential and widely read authors of popular science of his generation. Gould sp ...
said the ichthyosaur was his favorite example of
convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
.


Robotic fins

The use of fins for the propulsion of aquatic animals can be remarkably effective. It has been calculated that some fish can achieve a propulsive efficiency greater than 90%. Fish can accelerate and maneuver much more effectively than
boat A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats. Small boats are typically found on inl ...
s or
submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...
, and produce less water disturbance and noise. This has led to
biomimetic Biomimetics or biomimicry is the emulation of the models, systems, and elements of nature for the purpose of solving complex human problems. The terms "biomimetics" and "biomimicry" are derived from grc, βίος (''bios''), life, and μίμησ ...
studies of underwater robots which attempt to emulate the locomotion of aquatic animals. An example is the Robot Tuna built by th
Institute of Field Robotics
to analyze and mathematically model thunniform motion. In 2005, the
Sea Life London Aquarium The Sea Life London Aquarium is located on the ground floor of County Hall on the South Bank of the River Thames in central London, near the London Eye. It opened in March 1997 as the London Aquarium and hosts about one million visitors each ye ...
displayed three robotic fish created by the computer science department at the
University of Essex The University of Essex is a public university, public research university in Essex, England. Established by royal charter in 1965, Essex is one of the original plate glass university, plate glass universities. Essex's shield consists of the an ...
. The fish were designed to be autonomous, swimming around and avoiding obstacles like real fish. Their creator claimed that he was trying to combine "the speed of tuna, acceleration of a pike, and the navigating skills of an eel." The ''AquaPenguin'', developed by
Festo Festo is a German automation company based in Esslingen am Neckar, Germany. Festo produces and sells pneumatic and electrical control systems and drive technology for factories and process automation. Festo Didactic also offers industrial ed ...
of Germany, copies the streamlined shape and propulsion by front flippers of
penguin Penguins (order (biology), order List of Sphenisciformes by population, Sphenisciformes , family (biology), family Spheniscidae ) are a group of Water bird, aquatic flightless birds. They live almost exclusively in the Southern Hemisphere: on ...
s. Festo also developed ''AquaRay'', ''AquaJelly'' and ''AiraCuda'', respectively emulating the locomotion of manta rays, jellyfish and barracuda. In 2004, Hugh Herr at MIT prototyped a
biomechatronic Biomechatronics is an applied interdisciplinary science that aims to integrate biology and mechatronics (electrical, electronics, and mechanical engineering). It also encompasses the fields of robotics and neuroscience. Biomechatronic devices encom ...
robotic fish with a living
actuator An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover". An actuator requires a control device (controlled by control signal) a ...
by surgically transplanting muscles from frog legs to the robot and then making the robot swim by pulsing the muscle fibers with electricity. Robotic fish offer some research advantages, such as the ability to examine an individual part of a fish design in isolation from the rest of the fish. However, this risks oversimplifying the biology so key aspects of the animal design are overlooked. Robotic fish also allow researchers to vary a single parameter, such as flexibility or a specific motion control. Researchers can directly measure forces, which is not easy to do in live fish. "Robotic devices also facilitate three-dimensional kinematic studies and correlated hydrodynamic analyses, as the location of the locomotor surface can be known accurately. And, individual components of a natural motion (such as outstroke vs. instroke of a flapping appendage) can be programmed separately, which is certainly difficult to achieve when working with a live animal."


See also

*
Aquatic locomotion Aquatic locomotion or swimming is biologically propelled motion through a liquid medium. The simplest propulsive systems are composed of cilia and flagella. Swimming has evolved a number of times in a range of organisms including arthropods, fi ...
* Fin and flipper locomotion *
Fish locomotion Fish locomotion is the various types of animal locomotion used by fish, principally by swimming. This is achieved in different groups of fish by a variety of mechanisms of propulsion, most often by wave-like lateral flexions of the fish's body a ...
*
Robot locomotion Robot locomotion is the collective name for the various methods that robots use to transport themselves from place to place. Wheeled robots are typically quite energy efficient and simple to control. However, other forms of locomotion may be more ...
*
RoboTuna The RoboTuna is a robotic fish project involving a series of robotic fish designed and built by a team of scientists at the Massachusetts Institute of Technology (MIT) in the US. The Project The project started in 1993. Their aim was to inves ...
*
Sail (submarine) In naval parlance, the sail (American usage) or fin (British/Commonwealth usage) (also known as a fairwater) of a submarine is the tower-like structure found on the dorsal (topside) surface of submarines. Submarine sails once housed the conning to ...
* Surfboard fin


References


Further reading

* * Blake, Robert William (1983
''Fish Locomotion''
CUP Archive. . * * * * * * * Tangorra JL, CEsposito CJ and Lauder GV (2009
"Biorobotic fins for investigations of fish locomotion"
In: ''Intelligent Robots and Systems'', pages: 2120–2125. E-. * Tu X and Terzopoulos D (1994
"Artificial fishes: Physics, locomotion, perception, behavior"
In: ''Proceedings of the 21st annual conference on Computer graphics and interactive techniques'', pages 43–50. . *


External links



''Earthlife''.
Computational fluid dynamics tutorial
Many examples and images, with references to robotic fish.

University of British Columbia.
A fin-tuned design
''The Economist'', 19 November 2008. {{fins, limbs and wings Animal anatomy Watercraft components Rocketry