Exchange Coefficients

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Exchange Coefficients

Coefficients of eddy flux (e.g., of momentum, heat, water vapor, etc.) in turbulent flow, defined in analogy to those of the kinetic theory of gases (see eddy). Also called austausch coefficients, eddy coefficients, interchange coefficients. </dd>
The exchange-coefficient hypothesis states that the mean eddy flux per unit area of a conservative quantity (suitability expressed) is proportional to the gradient of the mean value of this quantity, that is,

Mean flux per unit area = -Ce (dMissing Image:img src="SP7-e_files/Ebar.gif"/ dN)
where Ce is the exchange

coefficient; E is the mean value of the quantity; and N is the direction normal to the surface. In strict analogy to molecular properties; Ce would be constant, for turbulent flow Ce turns out to depend on time and location. See eddy viscosity diffusivity. [[/a>|/a> ]]


This article is based on NASA's Dictionary of Technical Terms for Aerospace Use