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Lewis number

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The Lewis number for a given species <math> k </math> is
The Lewis number for a given species <math> k </math> is
:<math>
:<math>
-
Le_k = \frac{\lambda}{\rho C_p D_k}
+
Le_k \equiv \frac{\lambda}{\rho C_p D_k}
</math>
</math>
Denoting <math> D_{th}= \lambda / \rho C_p </math> the heat diffusivity coefficient the Lewis number
Denoting <math> D_{th}= \lambda / \rho C_p </math> the heat diffusivity coefficient the Lewis number
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In many combustion models, all species are assumed to diffuse at the same speed and therefore
In many combustion models, all species are assumed to diffuse at the same speed and therefore
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<math> Le=1 </math>
+
<math> Le \equiv 1 </math>
[[Category:Dimensionless parameters]]
[[Category:Dimensionless parameters]]

Revision as of 16:50, 17 November 2005

The Lewis number for a given species  k is


Le_k \equiv \frac{\lambda}{\rho C_p D_k}

Denoting  D_{th}= \lambda / \rho C_p the heat diffusivity coefficient the Lewis number can be expressed as


Le_k = \frac{D_{th}}{ D_k}

which is the ratio of the heat diffusion speed to the diffusion speed of species  k .

In many combustion models, all species are assumed to diffuse at the same speed and therefore  Le \equiv 1

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