Author: nick

A cartoon is a type of visual art that is typically drawn, frequently animated, in an unrealistic or semi-realistic style. The specific meaning has evolved, but the modern usage usually refers to either: an image or series of images intended for satire, caricature, or humor; or a motion picture that relies on a sequence of illustrations for its animation. Someone who creates cartoons in the first sense is called a cartoonist,^[1] and in the second sense they are usually called an animator.

The concept originated in the Middle Ages, and first described a preparatory drawing for a piece of art, such as a painting, fresco, tapestry, or stained glass window. In the 19th century, beginning in Punch magazine in 1843, cartoon came to refer – ironically at first – to humorous artworks in magazines and newspapers. Then it also was used for political cartoons and comic strips. When the medium developed, in the early 20th century, it began to refer to animated films that resembled print cartoons.^[2]

Fine art[edit]

A cartoon (from Italian: cartone and Dutch: karton—words describing strong, heavy paper or pasteboard) is a full-size drawing made on sturdy paper as a design or modello for a painting, stained glass, or tapestry. Cartoons were typically used in the production of frescoes, to accurately link the component parts of the composition when painted on damp plaster over a series of days (giornate).^[3] In media such as stained tapestry or stained glass, the cartoon was handed over by the artist to the skilled craftsmen who produced the final work.

Such cartoons often have pinpricks along the outlines of the design so that a bag of soot patted or "pounced" over a cartoon, held against the wall, would leave black dots on the plaster ("pouncing"). Cartoons by painters, such as the Raphael Cartoons in London, Francisco Goya's tapestry cartoons, and examples by Leonardo da Vinci, are highly prized in their own right. Tapestry cartoons, usually colored, could be placed behind the loom, where the weaver would replicate the design. As tapestries are worked from behind, a mirror could be placed behind the loom to allow the weaver to see their work; in such cases the cartoon was placed behind the weaver.^[2][4]

Mass media[edit]

In print media, a cartoon is a drawing or series of drawings, usually humorous in intent. This usage dates from 1843, when Punch magazine applied the term to satirical drawings in its pages,^[5] particularly sketches by John Leech.^[6] The first of these parodied the preparatory cartoons for grand historical frescoes in the then-new Palace of Westminster in London.^[7]

Sir John Tenniel—illustrator of Alice's Adventures in Wonderland—joined Punch in 1850, and over 50 years contributed over two thousand cartoons.^[8]

Cartoons can be divided into gag cartoons, which include editorial cartoons, and comic strips.

Modern single-panel gag cartoons, found in magazines, generally consist of a single drawing with a typeset caption positioned beneath, or, less often, a speech balloon.^[9] Newspaper syndicates have also distributed single-panel gag cartoons by Mel Calman, Bill Holman, Gary Larson, George Lichty, Fred Neher and others. Many consider New Yorker cartoonist Peter Arno the father of the modern gag cartoon (as did Arno himself).^[10] The roster of magazine gag cartoonists includes Charles Addams, Charles Barsotti, and Chon Day.

Comics
Speech balloon
Comics studies
Education Glossary History
Methods
Cartooning Photo comics
Media formats
Comic book Comic strip Digital comic Gag cartoon Trade paperback Graphic novel Political cartoon Webcomic Webtoon
Comics by country and culture
American comics Argentine comics Australian comics Bandes dessinées (Belgium / Quebec) Brazilian comics British comics (Welsh-language) Canadian comics Croatian comics Czech comics Dutch comics European comics German comics Hungarian comics Indian comics Irish comics Italian comics Manga Manhua (Hong Kong) Manhwa Mexican comics Pakistani comics Philippine comics Polish comics Portuguese comics Serbian comics South African comics Spanish comics Thai comics Turkish comics Vietnamese comics
Community
Awards Cartoonists Collecting Publishers Sales Writers
Comics portal
v t e

Bill Hoest, Jerry Marcus, and Virgil Partch began as magazine gag cartoonists and moved to syndicated comic strips. Richard Thompson illustrated numerous feature articles in The Washington Post before creating his Cul de Sac comic strip. The sports section of newspapers usually featured cartoons, sometimes including syndicated features such as Chester "Chet" Brown's All in Sport.

Editorial cartoons are found almost exclusively in news publications and news websites. Although they also employ humor, they are more serious in tone, commonly using irony or satire. The art usually acts as a visual metaphor to illustrate a point of view on current social or political topics. Editorial cartoons often include speech balloons and sometimes use multiple panels. Editorial cartoonists of note include Herblock, David Low, Jeff MacNelly, Mike Peters, and Gerald Scarfe.^[2]

Comic strips, also known as cartoon strips in the United Kingdom, are found daily in newspapers worldwide, and are usually a short series of cartoon illustrations in sequence. In the United States, they are not commonly called "cartoons" themselves, but rather "comics" or "funnies". Nonetheless, the creators of comic strips—as well as comic books and graphic novels—are usually referred to as "cartoonists". Although humor is the most prevalent subject matter, adventure and drama are also represented in this medium. Some noteworthy cartoonists of humorous comic strips are Scott Adams, Charles Schulz, E. C. Segar, Mort Walker and Bill Watterson.^[2]

Political[edit]

Political cartoons are like illustrated editorials that serve visual commentaries on political events. They offer subtle criticism which are cleverly quoted with humour and satire to the extent that the criticized does not get embittered.

The pictorial satire of William Hogarth is regarded as a precursor to the development of political cartoons in 18th century England.^[11] George Townshend produced some of the first overtly political cartoons and caricatures in the 1750s.^[11][12] The medium began to develop in the latter part of the 18th century under the direction of its great exponents, James Gillray and Thomas Rowlandson, both from London. Gillray explored the use of the medium for lampooning and caricature, and has been referred to as the father of the political cartoon.^[13] By calling the king, prime ministers and generals to account for their behaviour, many of Gillray's satires were directed against George III, depicting him as a pretentious buffoon, while the bulk of his work was dedicated to ridiculing the ambitions of revolutionary France and Napoleon.^[13] George Cruikshank became the leading cartoonist in the period following Gillray, from 1815 until the 1840s. His career was renowned for his social caricatures of English life for popular publications.

By the mid 19th century, major political newspapers in many other countries featured cartoons commenting on the politics of the day. Thomas Nast, in New York City, showed how realistic German drawing techniques could redefine American cartooning.^[14] His 160 cartoons relentlessly pursued the criminal characteristic of the Tweed machine in New York City, and helped bring it down. Indeed, Tweed was arrested in Spain when police identified him from Nast's cartoons.^[15] In Britain, Sir John Tenniel was the toast of London.^[16] In France under the July Monarchy, Honoré Daumier took up the new genre of political and social caricature, most famously lampooning the rotund King Louis Philippe.

Political cartoons can be humorous or satirical, sometimes with piercing effect. The target of the humor may complain, but can seldom fight back. Lawsuits have been very rare; the first successful lawsuit against a cartoonist in over a century in Britain came in 1921, when J. H. Thomas, the leader of the National Union of Railwaymen (NUR), initiated libel proceedings against the magazine of the British Communist Party. Thomas claimed defamation in the form of cartoons and words depicting the events of "Black Friday", when he allegedly betrayed the locked-out Miners' Federation. To Thomas, the framing of his image by the far left threatened to grievously degrade his character in the popular imagination. Soviet-inspired communism was a new element in European politics, and cartoonists unrestrained by tradition tested the boundaries of libel law. Thomas won the lawsuit and restored his reputation.^[17]

Scientific[edit]

Cartoons such as xkcd have also found their place in the world of science, mathematics, and technology. For example, the cartoon Wonderlab looked at daily life in the chemistry lab. In the U.S., one well-known cartoonist for these fields is Sidney Harris. Many of Gary Larson's cartoons have a scientific flavor.

Comic books[edit]

The first comic-strip cartoons were of a humorous tone.^[18] Notable early humor comics include the Swiss comic-strip book Mr. Vieux Bois (1837), the British strip Ally Sloper (first appearing in 1867) and the American strip Yellow Kid (first appearing in 1895).

In the United States in the 1930s, books with cartoons were magazine-format "American comic books" with original material, or occasionally reprints of newspaper comic strips.^[19]

In Britain in the 1930s, adventure comic magazines became quite popular, especially those published by DC Thomson; the publisher sent observers around the country to talk to boys and learn what they wanted to read about. The story line in magazines, comic books and cinema that most appealed to boys was the glamorous heroism of British soldiers fighting wars that were exciting and just.^[20] DC Thomson issued the first The Dandy Comic in December 1937. It had a revolutionary design that broke away from the usual children's comics that were published broadsheet in size and not very colourful. Thomson capitalized on its success with a similar product The Beano in 1938.^[21]

On some occasions, new gag cartoons have been created for book publication.

Animation[edit]

Because of the stylistic similarities between comic strips and early animated films, cartoon came to refer to animation, and the word cartoon is currently used in reference to both animated cartoons and gag cartoons.^[22] While animation designates any style of illustrated images seen in rapid succession to give the impression of movement, the word "cartoon" is most often used as a descriptor for television programs and short films aimed at children, possibly featuring anthropomorphized animals,^[23] superheroes, the adventures of child protagonists or related themes.

In the 1980s, cartoon was shortened to toon, referring to characters in animated productions. This term was popularized in 1988 by the combined live-action/animated film Who Framed Roger Rabbit, followed in 1990 by the animated TV series Tiny Toon Adventures.

See also[edit]

• Billy Ireland Cartoon Library & Museum
• Caricature
• Comics
• Comics studies
• List of cartoonists
• List of editorial cartoonists
• List of comic strips

References[edit]

In fluid dynamics, a vortex (pl.: vortices or vortexes)^[1][2] is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved.^[3][4] Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in the wake of a boat, and the winds surrounding a tropical cyclone, tornado or dust devil.

Vortices are a major component of turbulent flow. The distribution of velocity, vorticity (the curl of the flow velocity), as well as the concept of circulation are used to characterise vortices. In most vortices, the fluid flow velocity is greatest next to its axis and decreases in inverse proportion to the distance from the axis.

In the absence of external forces, viscous friction within the fluid tends to organise the flow into a collection of irrotational vortices, possibly superimposed to larger-scale flows, including larger-scale vortices. Once formed, vortices can move, stretch, twist, and interact in complex ways. A moving vortex carries some angular and linear momentum, energy, and mass, with it.

Overview[edit]

In the dynamics of fluid, a vortex is fluid that revolves around the axis line. This fluid might be curved or straight. Vortices form from stirred fluids: they might be observed in smoke rings, whirlpools, in the wake of a boat or the winds around a tornado or dust devil.

Vortices are an important part of turbulent flow. Vortices can otherwise be known as a circular motion of a liquid. In the cases of the absence of forces, the liquid settles. This makes the water stay still instead of moving.

When they are created, vortices can move, stretch, twist and interact in complicated ways. When a vortex is moving, sometimes, it can affect an angular position.

For an example, if a water bucket is rotated or spun constantly, it will rotate around an invisible line called the axis line. The rotation moves around in circles. In this example the rotation of the bucket creates extra force.

The reason that the vortices can change shape is the fact that they have open particle paths. This can create a moving vortex. Examples of this fact are the shapes of tornadoes and drain whirlpools.

When two or more vortices are close together they can merge to make a vortex. Vortices also hold energy in its rotation of the fluid. If the energy is never removed, it would consist of circular motion forever.

Properties[edit]

Vorticity[edit]

A key concept in the dynamics of vortices is the vorticity, a vector that describes the local rotary motion at a point in the fluid, as would be perceived by an observer that moves along with it. Conceptually, the vorticity could be observed by placing a tiny rough ball at the point in question, free to move with the fluid, and observing how it rotates about its center. The direction of the vorticity vector is defined to be the direction of the axis of rotation of this imaginary ball (according to the right-hand rule) while its length is twice the ball's angular velocity. Mathematically, the vorticity is defined as the curl (or rotational) of the velocity field of the fluid, usually denoted by ${displaystyle {vec {omega }}}$ and expressed by the vector analysis formula ${displaystyle abla imes {vec {mathit {u}}}}$, where ${displaystyle abla }$ is the nabla operator and ${displaystyle {vec {mathit {u}}}}$ is the local flow velocity.^[5]

The local rotation measured by the vorticity ${displaystyle {vec {omega }}}$ must not be confused with the angular velocity vector of that portion of the fluid with respect to the external environment or to any fixed axis. In a vortex, in particular, ${displaystyle {vec {omega }}}$ may be opposite to the mean angular velocity vector of the fluid relative to the vortex's axis.

Vortex types[edit]

In theory, the speed u of the particles (and, therefore, the vorticity) in a vortex may vary with the distance r from the axis in many ways. There are two important special cases, however:

• If the fluid rotates like a rigid body – that is, if the angular rotational velocity Ω is uniform, so that u increases proportionally to the distance r from the axis – a tiny ball carried by the flow would also rotate about its center as if it were part of that rigid body. In such a flow, the vorticity is the same everywhere: its direction is parallel to the rotation axis, and its magnitude is equal to twice the uniform angular velocity Ω of the fluid around the center of rotation.

  ${displaystyle {egin{aligned}{vec {Omega }}&=(0,0,Omega ),quad {vec {r}}=(x,y,0),\{vec {u}}&={vec {Omega }} imes {vec {r}}=(-Omega y,Omega x,0),\{vec {omega }}&= abla imes {vec {u}}=(0,0,2Omega )=2{vec {Omega }}.end{aligned}}}$

• If the particle speed u is inversely proportional to the distance r from the axis, then the imaginary test ball would not rotate over itself; it would maintain the same orientation while moving in a circle around the vortex axis. In this case the vorticity ${displaystyle {vec {omega }}}$ is zero at any point not on that axis, and the flow is said to be irrotational.

  ${displaystyle {egin{aligned}{vec {Omega }}&=left(0,0,alpha r^{-2} ight),quad {vec {r}}=(x,y,0),\{vec {u}}&={vec {Omega }} imes {vec {r}}=left(-alpha yr^{-2},alpha xr^{-2},0 ight),\{vec {omega }}&= abla imes {vec {u}}=0.end{aligned}}}$

Irrotational vortices[edit]

In the absence of external forces, a vortex usually evolves fairly quickly toward the irrotational flow pattern^{[citation needed]}, where the flow velocity u is inversely proportional to the distance r. Irrotational vortices are also called free vortices.

For an irrotational vortex, the circulation is zero along any closed contour that does not enclose the vortex axis; and has a fixed value, Γ, for any contour that does enclose the axis once.^[6] The tangential component of the particle velocity is then ${displaystyle u_{ heta }={ frac {Gamma }{2pi r}}}$. The angular momentum per unit mass relative to the vortex axis is therefore constant, ${displaystyle ru_{ heta }={ frac {Gamma }{2pi }}}$.

The ideal irrotational vortex flow in free space is not physically realizable, since it would imply that the particle speed (and hence the force needed to keep particles in their circular paths) would grow without bound as one approaches the vortex axis. Indeed, in real vortices there is always a core region surrounding the axis where the particle velocity stops increasing and then decreases to zero as r goes to zero. Within that region, the flow is no longer irrotational: the vorticity ${displaystyle {vec {omega }}}$ becomes non-zero, with direction roughly parallel to the vortex axis. The Rankine vortex is a model that assumes a rigid-body rotational flow where r is less than a fixed distance r₀, and irrotational flow outside that core regions.

In a viscous fluid, irrotational flow contains viscous dissipation everywhere, yet there are no net viscous forces, only viscous stresses.^[7] Due to the dissipation, this means that sustaining an irrotational viscous vortex requires continuous input of work at the core (for example, by steadily turning a cylinder at the core). In free space there is no energy input at the core, and thus the compact vorticity held in the core will naturally diffuse outwards, converting the core to a gradually-slowing and gradually-growing rigid-body flow, surrounded by the original irrotational flow. Such a decaying irrotational vortex has an exact solution of the viscous Navier–Stokes equations, known as a Lamb–Oseen vortex.

Rotational vortices[edit]

A rotational vortex – a vortex that rotates in the same way as a rigid body – cannot exist indefinitely in that state except through the application of some extra force, that is not generated by the fluid motion itself. It has non-zero vorticity everywhere outside the core. Rotational vortices are also called rigid-body vortices or forced vortices.

For example, if a water bucket is spun at constant angular speed w about its vertical axis, the water will eventually rotate in rigid-body fashion. The particles will then move along circles, with velocity u equal to wr.^[6] In that case, the free surface of the water will assume a parabolic shape.

In this situation, the rigid rotating enclosure provides an extra force, namely an extra pressure gradient in the water, directed inwards, that prevents transition of the rigid-body flow to the irrotational state.

Vortex formation on boundaries[edit]

Vortex structures are defined by their vorticity, the local rotation rate of fluid particles. They can be formed via the phenomenon known as boundary layer separation which can occur when a fluid moves over a surface and experiences a rapid acceleration from the fluid velocity to zero due to the no-slip condition. This rapid negative acceleration creates a boundary layer which causes a local rotation of fluid at the wall (i.e. vorticity) which is referred to as the wall shear rate. The thickness of this boundary layer is proportional to ${displaystyle surd (vt)}$ (where v is the free stream fluid velocity and t is time).

If the diameter or thickness of the vessel or fluid is less than the boundary layer thickness then the boundary layer will not separate and vortices will not form. However, when the boundary layer does grow beyond this critical boundary layer thickness then separation will occur which will generate vortices.

This boundary layer separation can also occur in the presence of combatting pressure gradients (i.e. a pressure that develops downstream). This is present in curved surfaces and general geometry changes like a convex surface. A unique example of severe geometric changes is at the trailing edge of a bluff body where the fluid flow deceleration, and therefore boundary layer and vortex formation, is located.

Another form of vortex formation on a boundary is when fluid flows perpendicularly into a wall and creates a splash effect. The velocity streamlines are immediately deflected and decelerated so that the boundary layer separates and forms a toroidal vortex ring.^[8]

Vortex geometry[edit]

In a stationary vortex, the typical streamline (a line that is everywhere tangent to the flow velocity vector) is a closed loop surrounding the axis; and each vortex line (a line that is everywhere tangent to the vorticity vector) is roughly parallel to the axis. A surface that is everywhere tangent to both flow velocity and vorticity is called a vortex tube. In general, vortex tubes are nested around the axis of rotation. The axis itself is one of the vortex lines, a limiting case of a vortex tube with zero diameter.

According to Helmholtz's theorems, a vortex line cannot start or end in the fluid – except momentarily, in non-steady flow, while the vortex is forming or dissipating. In general, vortex lines (in particular, the axis line) are either closed loops or end at the boundary of the fluid. A whirlpool is an example of the latter, namely a vortex in a body of water whose axis ends at the free surface. A vortex tube whose vortex lines are all closed will be a closed torus-like surface.

A newly created vortex will promptly extend and bend so as to eliminate any open-ended vortex lines. For example, when an airplane engine is started, a vortex usually forms ahead of each propeller, or the turbofan of each jet engine. One end of the vortex line is attached to the engine, while the other end usually stretches out and bends until it reaches the ground.

When vortices are made visible by smoke or ink trails, they may seem to have spiral pathlines or streamlines. However, this appearance is often an illusion and the fluid particles are moving in closed paths. The spiral streaks that are taken to be streamlines are in fact clouds of the marker fluid that originally spanned several vortex tubes and were stretched into spiral shapes by the non-uniform flow velocity distribution.

Pressure in a vortex[edit]

The fluid motion in a vortex creates a dynamic pressure (in addition to any hydrostatic pressure) that is lowest in the core region, closest to the axis, and increases as one moves away from it, in accordance with Bernoulli's principle. One can say that it is the gradient of this pressure that forces the fluid to follow a curved path around the axis.

In a rigid-body vortex flow of a fluid with constant density, the dynamic pressure is proportional to the square of the distance r from the axis. In a constant gravity field, the free surface of the liquid, if present, is a concave paraboloid.

In an irrotational vortex flow with constant fluid density and cylindrical symmetry, the dynamic pressure varies as P_∞ − K/r², where P_∞ is the limiting pressure infinitely far from the axis. This formula provides another constraint for the extent of the core, since the pressure cannot be negative. The free surface (if present) dips sharply near the axis line, with depth inversely proportional to r². The shape formed by the free surface is called a hyperboloid, or "Gabriel's Horn" (by Evangelista Torricelli).

The core of a vortex in air is sometimes visible because water vapor condenses as the low pressure of the core causes adiabatic cooling; the funnel of a tornado is an example. When a vortex line ends at a boundary surface, the reduced pressure may also draw matter from that surface into the core. For example, a dust devil is a column of dust picked up by the core of an air vortex attached to the ground. A vortex that ends at the free surface of a body of water (like the whirlpool that often forms over a bathtub drain) may draw a column of air down the core. The forward vortex extending from a jet engine of a parked airplane can suck water and small stones into the core and then into the engine.

Evolution[edit]

Vortices need not be steady-state features; they can move and change shape. In a moving vortex, the particle paths are not closed, but are open, loopy curves like helices and cycloids. A vortex flow might also be combined with a radial or axial flow pattern. In that case the streamlines and pathlines are not closed curves but spirals or helices, respectively. This is the case in tornadoes and in drain whirlpools. A vortex with helical streamlines is said to be solenoidal.

As long as the effects of viscosity and diffusion are negligible, the fluid in a moving vortex is carried along with it. In particular, the fluid in the core (and matter trapped by it) tends to remain in the core as the vortex moves about. This is a consequence of Helmholtz's second theorem. Thus vortices (unlike surface waves and pressure waves) can transport mass, energy and momentum over considerable distances compared to their size, with surprisingly little dispersion. This effect is demonstrated by smoke rings and exploited in vortex ring toys and guns.

Two or more vortices that are approximately parallel and circulating in the same direction will attract and eventually merge to form a single vortex, whose circulation will equal the sum of the circulations of the constituent vortices. For example, an airplane wing that is developing lift will create a sheet of small vortices at its trailing edge. These small vortices merge to form a single wingtip vortex, less than one wing chord downstream of that edge. This phenomenon also occurs with other active airfoils, such as propeller blades. On the other hand, two parallel vortices with opposite circulations (such as the two wingtip vortices of an airplane) tend to remain separate.

Vortices contain substantial energy in the circular motion of the fluid. In an ideal fluid this energy can never be dissipated and the vortex would persist forever. However, real fluids exhibit viscosity and this dissipates energy very slowly from the core of the vortex. It is only through dissipation of a vortex due to viscosity that a vortex line can end in the fluid, rather than at the boundary of the fluid.

Further examples[edit]

• In the hydrodynamic interpretation of the behaviour of electromagnetic fields, the acceleration of electric f