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Péclet number



In fluid dynamics, the Péclet number is a dimensionless number relating the rate of advection of a flow to its rate of diffusion, often thermal diffusion. It is equivalent to the product of the Reynolds number with the Prandtl number in the case of thermal diffusion, and the product of the Reynolds number with the Schmidt number in the case of mass diffusion.

Additional recommended knowledge

For thermal diffusion, the Péclet number is defined as:

\mathrm{Pe}_L = \frac{L V}{\alpha} = \mathrm{Re}_L \cdot \mathrm{Pr}.

For mass diffusion, it is defined as:

\mathrm{Pe}_L = \frac{L V}{D} = \mathrm{Re}_L \cdot \mathrm{Sc}

where

and

In engineering applications the Péclet number is often very large. In such situations, the dependency of the flow upon downstream locations is diminished, and variables in the flow tend to become 'one-way' properties. Thus, when modelling certain situations with high Péclet numbers, simpler computational models can be adopted.[1]

A flow will often have different Péclet numbers for heat and mass. This can lead to the phenomenon of Double-diffusive convection.

See also

References

  1. ^ Patankar, Numerical Heat Transfer and Fluid Flow, ISBN 0891165223, p 102
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Péclet_number". A list of authors is available in Wikipedia.
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