Turbulent flow around an obstacle; the flow further upstream is laminar

Laminar and turbulent water flow over the hull of a submarine

Turbulence in the tip vortex from an airplane wing

In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic, stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time. Flow that is not turbulent is called laminar flow. The (dimensionless) Reynolds number characterizes whether flow conditions lead to laminar or turbulent flow; e.g. for pipe flow, a Reynolds number above about 2300 will be turbulent. The statistical description of turbulent flow was suggested by the Russian mathematician Andrey Kolmogorov; this description is known to be approximate at best. Download high resolution version (480x640, 50 KB) Turbulent flow arouns an obstacle. ... Download high resolution version (480x640, 50 KB) Turbulent flow arouns an obstacle. ... The USS Los Angeles (SNN 688) Source: http://www. ... The USS Los Angeles (SNN 688) Source: http://www. ... Image File history File links Download high resolution version (2976x2420, 995 KB) Date 05. ... Image File history File links Download high resolution version (2976x2420, 995 KB) Date 05. ... Fluid dynamics is the subdiscipline of fluid mechanics that studies fluids (liquids and gases) in motion. ... Stochastic, from the Greek stochos or goal, means of, relating to, or characterized by conjecture; conjectural; random. ... In classical mechanics momentum (pl. ... Convection is the transfer of heat by currents within a fluid. ... Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. ... The velocity of an object is simply its speed in a particular direction. ... Laminar flow (bottom) and turbulent flow (top) over a submarine hull. ... Dimensional analysis is a conceptual tool often applied in physics, chemistry, and engineering to understand physical situations involving a mix of different kinds of physical quantities. ... The Reynolds number is the ratio of inertial forces (vsρ) to viscous forces (μ/L) and is used for determining whether a flow will be laminar or turbulent. ... Andrey Kolmogorov Andrey Nikolaevich Kolmogorov (Андре́й Никола́евич Колмого́ров) (kahl-mah-GAW-raff) (April 25, 1903 in Tambov - October 20, 1987 in Moscow) was a Soviet mathematician who made major advances in the fields of probability theory and topology. ...

Consider the flow of water over a simple smooth object, such as a sphere. At very low speeds the flow is laminar, i.e., the flow is smooth (though it may involve vortices on a large scale). As the speed increases, at some point the transition is made to turbulent ("chaotic") flow. In turbulent flow, unsteady vortices appear on many scales and interact with each other. Drag due to boundary layer skin friction increases. The structure and location of boundary layer separation often changes, sometimes resulting in a reduction of overall drag. Because laminar-turbulent transition is governed by Reynolds number, the same transition occurs if the size of the object is gradually increased, or the viscosity of the fluid is decreased, or if the density of the fluid is increased. A plot of the trajectory Lorenz system for values r = 28, σ = 10, b = 8/3 In mathematics and physics, chaos theory describes the behavior of certain nonlinear dynamical systems that under certain conditions exhibit a phenomenon known as chaos. ... It has been suggested that Drag equation be merged into this article or section. ... In physics and fluid mechanics, the boundary layer is that layer of fluid in the immediate vicinity of a bounding surface. ... The pitch drop experiment at the University of Queensland. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ...

Turbulence causes the formation of eddies which are defined by the Kolmogorov length scale and a turbulent diffusion coefficient. In large bodies of water like oceans this coefficient can be found using Richardson's four-third power law and is governed by the random walk principle. In rivers and large ocean currents, the diffusion coefficient is given by variations of Elder's formula. Andrey Kolmogorov Andrey Nikolaevich Kolmogorov (Андре́й Никола́евич Колмого́ров) (kahl-mah-GAW-raff) (April 25, 1903 in Tambov - October 20, 1987 in Moscow) was a Russian mathematician who made major advances in the fields of probability theory and topology. ... The Diffusion Coefficient is given by where D is the diffusion coefficient in dimensions of [length2 time-1] T is the temperature in dimensions of Kelvin R is the gas constant in dimensions of [energy temperature-1 parts-1] See also Ficks law of diffusion Categories: Science stubs ... Lewis Fry Richardson (October 11, 1881 - September 30, 1953) was a mathematician, physicist and psychologist. ... In mathematics and physics, a random walk, sometimes called a drunkards walk, is a formalisation of the intuitive idea of taking successive steps, each in a random direction. ...

When designing piping systems, turbulent flow requires a higher input of energy from a pump (or fan) than laminar flow. However, for applications such as heat exchangers and reaction vessels, turbulent flow is essential for good heat transfer and mixing.

Examples of turbulence

• A jet exhausting from a nozzle into a quiescent fluid. As the flow emerges into this external fluid, shear layers originating at the lips of the nozzle are created. These layers separate the fast moving jet from the external fluid, and at a certain critical Reynolds number they become unstable and break down to turbulence.
• Smoke rising from a cigarette. for the first few centimetres it remains laminar, and then becomes unstable and turbulent. Similarly, the dispersion of pollutants in the atmosphere is governed by turbulent processes.
• Flow over a golf ball. (This can be best understood by considering the golf ball to be stationary, with air flowing over it.) If the golf ball were smooth, the boundary layer flow over the front of the sphere would be laminar at typical conditions. However, the boundary layer would separate early, as the pressure gradient switched from favorable (pressure decreasing in the flow direction) to unfavorable (pressure increasing in the flow direction), creating a large region of low pressure behind the ball that creates high form drag. To prevent this from happening, the surface is dimpled to perturb the boundary layer and promote transition to turbulence. This results in higher skin friction, but moves the point of boundary layer separation further along, resulting in lower form drag and lower overall drag.
• The mixing of warm and cold air in the atmosphere by wind, which causes poor astronomical seeing (the blurring of images seen through the atmosphere)
• Most of the terrestrial atmospheric circulation
• The oceanic and atmospheric mixed layers and intense oceanic currents.
• The flow conditions in many industrial equipment (such as pipes, ducts, precipitators, gas scrubbers, etc.) and machines (for instance, internal combustion engines and gas turbines).
• The external flow over all kind of vehicles such as cars, airplanes, ships and submarines.
• The motions of matter in stellar atmospheres.

According to an apocryphal story, Werner Heisenberg was asked what he would ask God, given the opportunity. His reply was: "When I meet God, I am going to ask him two questions: Why relativity? And why turbulence? I really believe he will have an answer for the first." A similar witticism has been attributed to Horace Lamb (who had published a noted text book on Hydrodynamics)—his choice being quantum mechanics (instead of relativity) and turbulence. Lamb was quoted as saying in a speech to the British Association for the Advancement of Science, "I am an old man now, and when I die and go to heaven there are two matters on which I hope for enlightenment. One is quantum electrodynamics, and the other is the turbulent motion of fluids. And about the former I am rather optimistic." Smoke from a wildfire Smoke is a suspension in air (aerosol) of small particles resulting from incomplete combustion of a fuel. ... A lit cigarette A full ashtray. ... A golf ball on a Tee with a driver ready for a drive A golf ball is a ball designed for use in the game of golf. ... Schematic diagram illustrating how optical wavefronts from a distant star may be perturbed by a turbulent layer in the atmosphere. ... Werner Heisenberg Werner Karl Heisenberg (December 5, 1901 – February 1, 1976) was a celebrated German physicist and Nobel laureate, one of the founders of quantum mechanics. ... Michelangelos depiction of God in the painting Creation of the Sun and Moon in the Sistine Chapel Krishna, the eighth incarnation of Vishnu, one of the manifestations of the ultimate reality or God in Hinduism This article discusses the term God in the context of monotheism and henotheism. ... Sir Horace Lamb FRS (November 29, 1849 - December 4, 1934) was a British applied mathematician and author of several influential texts on classical physics, among them Hydrodynamics (1895) and Dynamical Theory of Sound (1910). ... Hydrodynamics is fluid dynamics applied to liquids, such as water, alcohol, oil, and blood. ...

Unsolved problems in physics: Is it possible to make a theoretical model to describe the behavior of a turbulent fluid—in particular, its internal structures?

Image File history File links Question_dropshade. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

See also

• Astronomical seeing
• Clear-Air Turbulence
• Downdrafts
• Fluid dynamics
  • Navier-Stokes equations
  • Poiseuille's law
  • Darcy-Weisbach equation
• Mesocyclones
• Vortex
• Vortex generator
• Chaos theory
• Wingtip vortices
• Wake turbulence
• Swing bowling
• Velocimetry

Schematic diagram illustrating how optical wavefronts from a distant star may be perturbed by a turbulent layer in the atmosphere. ... Clear-Air Turbulence (often abbreviated CAT and sometimes colloquially referred to as air pockets) is the erratic movement of air masses in the absence of any visual cues (such as clouds). ... A downdraft is downward moving air, usually the direct result of air convection within the thunderstorm. ... Fluid dynamics is the subdiscipline of fluid mechanics that studies fluids (liquids and gases) in motion. ... The Navier-Stokes equations, named after Claude-Louis Navier and George Gabriel Stokes, are a set of equations that describe the motion of fluid substances like liquids and gases. ... The Poiseuilles law (or the Hagen-Poiseuille law also named after Gotthilf Heinrich Ludwig Hagen (1797-1884) for his experiments in 1839) is the physical law concerning the voluminal laminar stationary flow ΦV of incompressible uniform viscous liquid (so called Newtonian fluid) through a cylindrical tube with the constant... The Darcy-Weisbach equation is an important and widely used equation in hydraulics. ... This article or section may be confusing for some readers, and should be edited to be clearer or more simplified. ... Vortex created by the passage of an aircraft wing, revealed by coloured smoke A vortex is a spinning, often turbulent, flow (or any spiral motion) with closed streamlines. ... 1967 Model Cessna 182K in flight showing after-market vortex generators on the wing leading edge A vortex generator is an aerodynamic surface, basically a small vane, that creates a vortex. ... A plot of the trajectory Lorenz system for values r = 28, σ = 10, b = 8/3 In mathematics and physics, chaos theory describes the behavior of certain nonlinear dynamical systems that under certain conditions exhibit a phenomenon known as chaos. ... It has been suggested that this article or section be merged with Wake turbulence. ... Wake turbulence, also known as jetwash, are vortices that are formed any time an airfoil is producing lift. ... Swing bowling is a technique used for bowling in the sport of cricket. ... Velocimetry is the measurement of the velocity of fluids, as often used to solve fluid dynamics problems, or to study fluid networks, as well as in industrial and process control applications, or in the creation of new kinds of fluid flow sensors. ...

External links

• Center for Turbulence Research, Stanford University
• Journal of Turbulence, Institute of Physics
• Scientific American article
• Air Turbulence Forecast