Turbulence

turbulentturbulent flowatmospheric turbulenceturbulent mixingfluid turbulenceturbulent flowsturbulent airflowturbulent diffusionTurbulent forcesturbulently
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity.wikipedia
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Drag (physics)

dragaerodynamic dragair resistance
In general terms, in turbulent flow, unsteady vortices appear of many sizes which interact with each other, consequently drag due to friction effects increases.
Drag force is proportional to the velocity for a laminar flow and the squared velocity for a turbulent flow.

Laminar flow

laminarlaminar-flowlaminar air flow
It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between those layers.
When a fluid is flowing through a closed channel such as a pipe or between two flat plates, either of two types of flow may occur depending on the velocity and viscosity of the fluid: laminar flow or turbulent flow.

Clear-air turbulence

clear air turbulenceturbulenceair turbulence
Clear-air turbulence (CAT) is the turbulent movement of air masses in the absence of any visual clues, such as clouds, and is caused when bodies of air moving at widely different speeds meet.

Astronomical seeing

seeingatmospheric seeingatmospheric turbulence
Astronomical seeing refers to the amount of apparent blurring and twinkling of astronomical objects like stars due to turbulent mixing in the atmosphere of Earth, causing variations of the optical refractive index.

Plume (fluid dynamics)

plumeplumesPlume (hydrodynamics)
A further phenomenon of importance is whether a plume has laminar flow or turbulent flow.

Reynolds number

ReynoldsReynolds numbersRe
The onset of turbulence can be predicted by the dimensionless Reynolds number, the ratio of kinetic energy to viscous damping in a fluid flow. The onset of turbulence can be, to some extent, predicted by the Reynolds number, which is the ratio of inertial forces to viscous forces within a fluid which is subject to relative internal movement due to different fluid velocities, in what is known as a boundary layer in the case of a bounding surface such as the interior of a pipe.
With respect to laminar and turbulent flow regimes:

Mixed layer

mixed layer depthvertical mixingmixed surface layer
Turbulence typically plays a role in the formation of fluid mixed layers.

Dynamic scraped surface heat exchanger

(dynamic) scraped surface heat exchanger
removing the fouling layers, increasing turbulence in case of high viscosity flow, and avoiding the generation of ice and other process by-products.

Bruit

bruitsarterial bruitsCardiac bruit
Bruit, also called vascular murmur, is the abnormal sound generated by turbulent flow of blood in an artery due to either an area of partial obstruction or a localized high rate of blood flow through an unobstructed artery.

Boundary layer

boundary layersboundary layer theoryboundary-layer
The onset of turbulence can be, to some extent, predicted by the Reynolds number, which is the ratio of inertial forces to viscous forces within a fluid which is subject to relative internal movement due to different fluid velocities, in what is known as a boundary layer in the case of a bounding surface such as the interior of a pipe.
However, the boundary layer inevitably thickens and becomes less stable as the flow develops along the body, and eventually becomes turbulent, the process known as boundary layer transition.

Kolmogorov microscales

Kolmogorov length scaleKolmogorov scale
The scale at which this happens is the Kolmogorov length scale.
Kolmogorov microscales are the smallest scales in turbulent flow.

Taylor microscale

The Taylor microscale, which is sometimes called the turbulence length scale, is a length scale used to characterize a turbulent fluid flow.

Werner Heisenberg

HeisenbergW. HeisenbergHeisenberg, Werner
According to an apocryphal story, Werner Heisenberg was asked what he would ask God, given the opportunity.
He also made important contributions to the theories of the hydrodynamics of turbulent flows, the atomic nucleus, ferromagnetism, cosmic rays, and subatomic particles, and he was instrumental in planning the first West German nuclear reactor at Karlsruhe, together with a research reactor in Munich, in 1957.

Energy cascade

cascade models
Via this energy cascade, turbulent flow can be realized as a superposition of a spectrum of flow velocity fluctuations and eddies upon a mean flow.
This concept plays an important role in the study of well-developed turbulence.

Lewis Fry Richardson

Lewis RichardsonRichardsonLewis F. Richardson
For instance, 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. The Russian mathematician Andrey Kolmogorov proposed the first statistical theory of turbulence, based on the aforementioned notion of the energy cascade (an idea originally introduced by Richardson) and the concept of self-similarity.
He was also interested in atmospheric turbulence and performed many terrestrial experiments.

Inviscid flow

inviscidinviscid fluiddissipation-less limit
The energy "cascades" from these large-scale structures to smaller scale structures by an inertial and essentially inviscid mechanism.
These "inviscid flow arrangements" are vortex-like and may play a key role in the formation of the tornado, the tropical cyclone, and turbulence.

Snow fence

snow fencingsnowfence
Snow fences work by causing turbulence in the wind, such that it drops much of its snow load on the lee side of the fence.

Vortex

vorticesvorticalvortex lines
In general terms, in turbulent flow, unsteady vortices appear of many sizes which interact with each other, consequently drag due to friction effects increases.
Vortices are a major component of turbulent flow.

Parasitic drag

form draginterference dragdrag
:For comparison, the turbulent empirical relation known as the 1/7 Power Law (derived by Theodore von Kármán) is:

Fluid dynamics

hydrodynamicshydrodynamicfluid flow
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity.
Turbulent flows are unsteady by definition.

Vortex stretching

stretchingstretching the vortexvortex tubes
;Rotationality : Turbulent flows have non-zero vorticity and are characterized by a strong three-dimensional vortex generation mechanism known as vortex stretching.
Vortex stretching is at the core of the description of the turbulence energy cascade from the large scales to the small scales in turbulence.

Andrey Kolmogorov

KolmogorovAndrei KolmogorovA. N. Kolmogorov
The Russian mathematician Andrey Kolmogorov proposed the first statistical theory of turbulence, based on the aforementioned notion of the energy cascade (an idea originally introduced by Richardson) and the concept of self-similarity.
Andrey Nikolaevich Kolmogorov (, 25 April 1903 – 20 October 1987) was a Soviet mathematician who made significant contributions to the mathematics of probability theory, topology, intuitionistic logic, turbulence, classical mechanics, algorithmic information theory and computational complexity.

Dissipation

dissipateddissipativepower dissipation
;Dissipation : To sustain turbulent flow, a persistent source of energy supply is required because turbulence dissipates rapidly as the kinetic energy is converted into internal energy by viscous shear stress.
Waves or oscillations, lose energy over time, typically from friction or turbulence.

Large eddy simulation

LESlarge-eddy simulationLarge Eddy Simulation (LES)
Large eddy simulation (LES) is a mathematical model for turbulence used in computational fluid dynamics.

Navier–Stokes equations

Navier-Stokes equationsNavier-Stokes equationNavier–Stokes equation
Although it is possible to find some particular solutions of the Navier–Stokes equations governing fluid motion, all such solutions are unstable to finite perturbations at large Reynolds numbers.
The nonlinearity makes most problems difficult or impossible to solve and is the main contributor to the turbulence that the equations model.