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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
can be expressed as
can be expressed as
:<math>
:<math>
-
Le_k = \frac{D_{th}}{ D_k}
+
Le_k \equiv \frac{D_{th}}{ D_k}
</math>
</math>
which is the ratio of the heat diffusion speed to the diffusion speed of species <math> k </math>.
which is the ratio of the heat diffusion speed to the diffusion speed of species <math> k </math>.
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
-
<math> Le=1 </math>
+
<math> Le = 1 </math>
[[Category:Dimensionless parameters]]
[[Category:Dimensionless parameters]]

Latest revision as of 09:55, 17 December 2008

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 \equiv \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 = 1

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