Momentum flux: Difference between revisions
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{{Term | |||
|Display title=momentum flux | |||
{{ | |Definitions={{Definition | ||
|Num=1 | |||
|Meaning=The vertical [[flux]] of horizontal [[momentum]], equal to the force per unit area, or [[stress]]. | |||
|Explanation=The [[Reynolds stresses|Reynolds stress]] (τ<sub>''R''</sub>) can be determined from the [[covariance]] of the fluctuations of the horizontal (''u''′, ''v''′) and vertical (''w''′) [[wind]] components, by <blockquote>[[File:ams2001glos-Me28.gif|link=|center|ams2001glos-Me28]]</blockquote> where ρ is air density. A direct measurement is possible with eddy-correlation techniques, or an indirect determination can be made using [[Monin–Obukhov similarity theory|Monin–Obukhov similarity]] flux-profile relationships (<br/>''also called'' [[universal functions]]). The relation between the [[velocity]] scale ([[friction velocity]] ''u''<sub>*</sub>) and the momentum flux is <blockquote>[[File:ams2001glos-Me29.gif|link=|center|ams2001glos-Me29]]</blockquote> Momentum flux can be associated with either [[mean velocity]] components, internal [[gravity waves]], or with turbulent velocity fluctuations. For [[turbulence]], the momentum flux is also called the Reynolds stress. For waves, it is related to [[mountain wave]] drag. | |||
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Latest revision as of 12:05, 29 March 2024
The vertical flux of horizontal momentum, equal to the force per unit area, or stress.
The Reynolds stress (τR) can be determined from the covariance of the fluctuations of the horizontal (u′, v′) and vertical (w′) wind components, by
also called universal functions). The relation between the velocity scale (friction velocity u*) and the momentum flux is
where ρ is air density. A direct measurement is possible with eddy-correlation techniques, or an indirect determination can be made using Monin–Obukhov similarity flux-profile relationships (
also called universal functions). The relation between the velocity scale (friction velocity u*) and the momentum flux is
Momentum flux can be associated with either mean velocity components, internal gravity waves, or with turbulent velocity fluctuations. For turbulence, the momentum flux is also called the Reynolds stress. For waves, it is related to mountain wave drag.
