Talk:Lewis number

Isn't the Lewis number the ratio of the thermal diffusivity to the self diffusion co-efficient, rather than just mass diffusion?

The self diffusion coefficient being the rate of transport of a species compared to the concentration gradient of the species, with zero molecular transport? Thus a binary diffusion coefficient is possible if two different gasses are involved...

Source: Strehlow, R. A. 1984. Combustion fundamentals, McGraw-Hill series in Energy Combustion and Environment, McGraw-Hill Books, New York. 155.198.66.52 (talk) 12:22, 25 February 2008 (UTC)

Definition of the Lewis number and consistent relation between the Lewis number, the Prandtl number and the Schmidt number
The definition of the Lewis number written here is the ratio of the diffusion transport to the thermal conduction transport. However, in the current text of the article it is written that it is the ratio of thermal diffusivity to the mass diffusivity, which is the inverse of what is expressed in the equation. Following, J.D. Andersonś book Hypersonic and High-Temperature Gas Dynamics the Lewis number is defined as in the equation shown in the article (ratio of the diffusion transport to the thermal conduction transport). I think the text should be changed in this regard.

In addition, for this definition of the Lewis number, its consistent relation with the Prandtl and the Schmidt numbers is Le = Pr/Sc, which is the inverse of what is written in the article. So I think this should also be modified. — Preceding unsigned comment added by 2A02:A03F:6A4B:4800:F5EA:F93C:3A2:3106 (talk) 09:35, 10 October 2020 (UTC)

Agreed. I added a mention that this alternative definition (inverse of the one given) exist with references. I don't have access to Anderson's book, so it may provide more support if anyone can reference it. The current definition given in the article is the one given by the IAUPC, which is internationally recognized and held in high regard so I don't think we can disregard that definition. I haven't done a lot of research, so I think whichever definition is more common should be the one written explicitly, with the other still mentioned in the text. --2607:9880:42C7:FFFC:584C:61B6:F27C:7D54 (talk) 17:12, 11 November 2022 (UTC)