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第7行： + + − − − In [[fluid dynamics]], '''turbulence''' or '''turbulent flow''' is fluid motion characterized by [[Chaos theory|chaotic]] changes in [[pressure]] and [[flow velocity]]. It is in contrast to a [[laminar flow]], which occurs when a fluid flows in parallel layers, with no disruption between those layers.<ref name="Batchelor">{{cite book | last=Batchelor | first=G. | title=Introduction to Fluid Mechanics | year=2000}}</ref> − − 在流体力学中，湍流或紊流是以压力和流速的混乱变化为特征的流体运动。相反，层流是指流体在无互相干扰和中断的平行层中流动。 第20行：
第17行： − 可以在日常现象中观察到湍流，如拍岸海浪（激浪）、快速流动的的河水、翻腾的风暴云或从烟囱中冒出的烟。大多数在自然界发生或在工程应用中产生的流体运动都是湍流。湍流是由于流体的部分动能过大，克服了流体粘度的阻尼效应而引起的。因此，湍流通常在低粘度流体中出现。一般来说，湍流中会出现许多大小不一的不稳定涡流，它们相互作用，从而增加了摩擦效应产生的阻力，也增加了泵送流体通过管道所需的能量。湍流可以被利用，例如，飞机上的空气动力扰流器等装置可以 "破坏 "层流以增加阻力和减少升力。+ 第28行：
第25行： − 湍流的发生可以通过无量纲雷诺数来预测，雷诺数是流体动能与粘性阻尼的比率。然而，对湍流的详细物理学分析难以开展，且湍流内部的相互作用非常复杂。理查德-费曼将湍流形容为经典物理学中最重要的未解决之问题。+ 第38行：
第35行： − Laminar and turbulent water flow over the hull of a submarine. As the relative velocity of the water increases turbulence occurs.]] − + − tip vortex from an airplane wing]] − + − + − − * 烟雾从一支香烟上升起。最开始的几厘米，烟雾是层流。'''<font color="#ff8000"> 雷诺数Reynolds number </font>'''随着流速和特征长度增加时，飘起来的烟变成了湍流。 − − * 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, the surface is dimpled to perturb the boundary layer and promote turbulence. This results in higher skin friction, but it moves the point of boundary layer separation further along, resulting in lower drag. − +
→Examples of turbulence
In [[fluid dynamics]], '''turbulence''' or '''turbulent flow''' is fluid motion characterized by [[Chaos theory|chaotic]] changes in [[pressure]] and [[flow velocity]]. It is in contrast to a [[laminar flow]], which occurs when a fluid flows in parallel layers, with no disruption between those layers.<ref name="Batchelor">{{cite book | last=Batchelor | first=G. | title=Introduction to Fluid Mechanics | year=2000}}</ref>
在流体力学（[[fluid dynamics]]）中，湍流或紊流是以压力和流速（[[flow velocity]]）的混乱变化为特征的流体运动。相反，层流（ [[laminar flow]]）是指流体在无互相干扰和中断的平行层中流动。
Turbulence is commonly observed in everyday phenomena such as [[Breaking wave|surf]], fast flowing rivers, billowing storm clouds, or smoke from a chimney, and most fluid flows occurring in nature or created in engineering applications are turbulent.<ref name="ting-surf">{{cite journal|journal=Coastal Engineering|volume=27|issue=3–4|pages=131–160|year=1996|title=Dynamics of surf-zone turbulence in a spilling breaker|last1=Ting|first1=F. C. K.|last2=Kirby|first2=J. T.|url=|doi=10.1016/0378-3839(95)00037-2}}</ref><ref name="tennekes">{{cite book|last1=Tennekes|first1=H.|last2=Lumley|first2=J. L.|title=A First Course in Turbulence|year=1972|publisher=[[MIT Press]]|url=https://mitpress.mit.edu/books/first-course-turbulence}}</ref>{{rp|2}} Turbulence is caused by excessive kinetic energy in parts of a fluid flow, which overcomes the damping effect of the fluid's viscosity. For this reason turbulence is commonly realized in low viscosity fluids. In general terms, in turbulent flow, unsteady [[vortices]] appear of many sizes which interact with each other, consequently [[Drag (physics)|drag]] due to friction effects increases. This increases the energy needed to pump fluid through a pipe. Turbulence can be exploited, for example, by devices such as aerodynamic [[spoiler (aeronautics)|spoilers]] on aircraft that "spoil" the laminar flow to increase drag and reduce lift.
Turbulence is commonly observed in everyday phenomena such as [[Breaking wave|surf]], fast flowing rivers, billowing storm clouds, or smoke from a chimney, and most fluid flows occurring in nature or created in engineering applications are turbulent.<ref name="ting-surf">{{cite journal|journal=Coastal Engineering|volume=27|issue=3–4|pages=131–160|year=1996|title=Dynamics of surf-zone turbulence in a spilling breaker|last1=Ting|first1=F. C. K.|last2=Kirby|first2=J. T.|url=|doi=10.1016/0378-3839(95)00037-2}}</ref><ref name="tennekes">{{cite book|last1=Tennekes|first1=H.|last2=Lumley|first2=J. L.|title=A First Course in Turbulence|year=1972|publisher=[[MIT Press]]|url=https://mitpress.mit.edu/books/first-course-turbulence}}</ref>{{rp|2}} Turbulence is caused by excessive kinetic energy in parts of a fluid flow, which overcomes the damping effect of the fluid's viscosity. For this reason turbulence is commonly realized in low viscosity fluids. In general terms, in turbulent flow, unsteady [[vortices]] appear of many sizes which interact with each other, consequently [[Drag (physics)|drag]] due to friction effects increases. This increases the energy needed to pump fluid through a pipe. Turbulence can be exploited, for example, by devices such as aerodynamic [[spoiler (aeronautics)|spoilers]] on aircraft that "spoil" the laminar flow to increase drag and reduce lift.
可以在日常现象中观察到湍流，如拍岸海浪（[[Breaking wave|surf]]）、快速流动的的河水、翻腾的风暴云或从烟囱中冒出的烟。大多数在自然界发生或在工程应用中产生的流体运动都是湍流。湍流是由于流体的部分动能过大，克服了流体粘度的阻尼效应而引起的。因此，湍流通常在低粘度流体中出现。一般来说，湍流中会出现许多大小不一的不稳定涡流（[[vortices]]），它们相互作用，从而增加了摩擦效应产生的阻力（[[Drag (physics)|drag]]），也增加了泵送流体通过管道所需的能量。湍流可以被利用，例如，飞机上的空气动力扰流器（[[spoiler (aeronautics)|spoilers]]）等装置可以 "破坏 "层流以增加阻力和减少升力。
The onset of turbulence can be predicted by the dimensionless [[Reynolds number]], the ratio of kinetic energy to viscous damping in a fluid flow. However, turbulence has long resisted detailed physical analysis, and the interactions within turbulence create a very complex phenomenon. [[Richard Feynman]] has described turbulence as the most important unsolved problem in classical physics.<ref name="eames-quoting-feynman">{{cite journal|journal=[[Philosophical Transactions of the Royal Society A]]|title=New developments in understanding interfacial processes in turbulent flows|last1=Eames|first1=I.|last2=Flor|first2=J. B.|date=January 17, 2011|url=http://rsta.royalsocietypublishing.org/content/369/1937/702|doi=10.1098/rsta.2010.0332|pmid=21242127|bibcode=2011RSPTA.369..702E|volume=369|issue=1937|pages=702–705|doi-access=free}}</ref>
The onset of turbulence can be predicted by the dimensionless [[Reynolds number]], the ratio of kinetic energy to viscous damping in a fluid flow. However, turbulence has long resisted detailed physical analysis, and the interactions within turbulence create a very complex phenomenon. [[Richard Feynman]] has described turbulence as the most important unsolved problem in classical physics.<ref name="eames-quoting-feynman">{{cite journal|journal=[[Philosophical Transactions of the Royal Society A]]|title=New developments in understanding interfacial processes in turbulent flows|last1=Eames|first1=I.|last2=Flor|first2=J. B.|date=January 17, 2011|url=http://rsta.royalsocietypublishing.org/content/369/1937/702|doi=10.1098/rsta.2010.0332|pmid=21242127|bibcode=2011RSPTA.369..702E|volume=369|issue=1937|pages=702–705|doi-access=free}}</ref>
湍流的发生可以通过无量纲雷诺数（[[Reynolds number]]）来预测，雷诺数是流体动能与粘性阻尼的比率。然而，对湍流的详细物理学分析难以开展，且湍流内部的相互作用非常复杂。理查德-费曼（[[Richard Feynman]] ）将湍流形容为经典物理学中最重要的未解决之问题。
[[File:Los Angeles attack sub 2.jpg|thumb|right|[[Laminar flow|Laminar]] and turbulent water flow over the hull of a submarine. As the relative velocity of the water increases turbulence occurs.|链接=Special:FilePath/Los_Angeles_attack_sub_2.jpg]]
[[File:Los Angeles attack sub 2.jpg|thumb|right|[[Laminar flow|Laminar]] and turbulent water flow over the hull of a submarine. As the relative velocity of the water increases turbulence occurs.|链接=Special:FilePath/Los_Angeles_attack_sub_2.jpg]]
【图1：Laminar and turbulent water flow over the hull of a submarine. As the relative velocity of the water increases turbulence occurs.潜艇外壳层流和紊流水流。随着相对速度的增加，湍流出现。】
【图1：Laminar and turbulent water flow over the hull of a submarine. As the relative velocity of the water increases turbulence occurs. 潜艇船体外，水的层流和紊流。湍流随着水的相对速度增加而出现。】
[[File:Airplane vortex edit.jpg|thumb|right|Turbulence in the [[Wingtip vortices|tip vortex]] from an [[airplane]] wing]]
[[File:Airplane vortex edit.jpg|thumb|right|Turbulence in the [[Wingtip vortices|tip vortex]] from an [[airplane]] wing]]
【图2：tip vortex from an airplane wing飞机机翼上的涡流】
【图2：tip vortex from an airplane wing飞机机翼上的翼尖涡流】
* Smoke rising from a [[cigarette]]. For the first few centimeters, the smoke is [[Laminar flow|laminar]]. The smoke [[Plume (fluid dynamics)|plume]] becomes turbulent as its [[Reynolds number]] increases with increases in flow velocity and characteristic lengthscale.
* Smoke rising from a [[cigarette]]. For the first few centimeters, the smoke is [[Laminar flow|laminar]]. The smoke [[Plume (fluid dynamics)|plume]] becomes turbulent as its [[Reynolds number]] increases with increases in flow velocity and characteristic lengthscale.
* Smoke rising from a [[cigarette]]. For the first few centimeters, the smoke is [[Laminar flow|laminar]]. The smoke [[Plume (fluid dynamics)|plume]] becomes turbulent as its [[Reynolds number]] increases with increases in flow velocity and characteristic lengthscale.
* 烟雾从一支香烟上升起。最初的几厘米，烟雾是层流。'''<font color="#ff8000"> 雷诺数Reynolds number </font>'''随着流速和特征长度增加，烟雾羽流（[[Plume (fluid dynamics)|plume]]）变成了湍流。
* 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, the surface is dimpled to perturb the boundary layer and promote turbulence. This results in higher skin friction, but it moves the point of boundary layer separation further along, resulting in lower drag.
* 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, the surface is dimpled to perturb the boundary layer and promote turbulence. This results in higher skin friction, but it moves the point of boundary layer separation further along, resulting in lower drag.
* 流体流过高尔夫球。 （假设高尔夫球是静止的，而空气在上面流动是最好的理解方式。）如果高尔夫球是光滑的，则在典型条件下，典型情况下球体前部的'''<font color="#ff8000"> 边界层boundary layer</font>'''会出现层流。 但是，边界层会快速分离，因为压力梯度会从顺压（沿流动方向的压力减小）切换到逆压（沿流动方向的压力增大），从而在球后产生较大的低压区域，从而产生较高的形式阻力。 在球的表面加上凹槽以扰动边界层并促进湍流。 这会导致较高的皮肤摩擦，但会进一步移动边界层分离点，从而导致阻力减少。
* 流体流过高尔夫球。 （假设高尔夫球静止，而空气在上面流动，最容易的理解。）如果高尔夫球是光滑的，则在典型条件下，球体前部的'''<font color="#ff8000"> 边界层boundary layer</font>'''会出现层流。 但是，边界层会提前分离，因为压力梯度会从顺压（压力沿流动方向减小）切换到逆压（压力沿流动方向增大），从而在球后形成一个大低压区，产生较高的型阻（[[form drag]]）。 在球的表面加上凹槽以扰动边界层并促进湍流。 这会导致较高的皮肤摩擦，但会进一步移动边界层分离点，从而导致阻力减少。
*[[Clear-air turbulence]] experienced during airplane flight, as well as poor [[astronomical seeing]] (the blurring of images seen through the atmosphere).
*[[Clear-air turbulence]] experienced during airplane flight, as well as poor [[astronomical seeing]] (the blurring of images seen through the atmosphere).