Talk:Péclet number

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Relative magnitude of the Peclet number

Is it worth saying that values of the Peclet number are typically very large in most engineering applications? 128.12.20.32 21:49, 21 February 2006 (UTC)

Absolutely. I think that is a useful piece of information and I have added it to the article. Thanks.--Commander Keane 22:04, 21 February 2006 (UTC)

The phrase 'very large' is meaningless. One has to provide at least an example of the magnitude in engineering applications, and possibly also relate it to 'other applications' where it is smaller. Berland 07:22, 18 January 2007 (UTC)

I disagree: the Peclet number is dimensionless, and for such a number 'very large' is well understood to mean much greater than one. Chrisjohnson 12:08, 26 March 2007 (UTC)

I have a source that states that for epitaxial crystal growth the Peclet number is typically "very small." I was wondering if anyone knows of the reason for a "very small" Peclet number in epitaxial growth, but a "very large" Peclet number in most engineering applications? I refer to the article by E and Yip titled "Continuum Theory of Epitaxial Crystal Growth. I" published in the Journal of Statistical Physics, Vol. 104, 2001. —Preceding unsigned comment added by 128.163.129.103 (talk) 13:35, 2 October 2007 (UTC)

I disagree that in "most engineering application Peclet number is 'very large'". What do you define engineering application here? Peclet number is only considered in engineering when it is >>1, otherwise it's not. I know what I'm saying may sound trivial, but I find that the current wording is wrong.--Phoebontas (talk) 11:37, 23 May 2008 (UTC)

Better definition?

A Peclet number is typically a ratio of the time scale for diffusive flux of some quantity to the time scale for convective flux of that quantity. The quantity doesn't have to be heat, as is described here. For example, a Peclet number can easily be defined for problems in mass transport, where the quantity of interest is the concentration of some chemical species. Thoughts?

Yes, this is something of interest for igneous petrologists - how does the equation differ? And is it also referred to as a Peclet number or is the name modified?

I have seen the Peclet number written for mass transport as the product of the Schmidt and Reynolds number. Thus it could be written:- Pe = lv/D where D is some appropriate diffusion coefficient (or mass diffusivity). Its use is common in literature but don't have a specific citation for it.

I've done a fair bit of tidying up, putting mass diffusion and thermal diffusion on equal footings and removing some unnecessary definitions (they were all trivially equivalent). Chrisjohnson 12:08, 26 March 2007 (UTC)

The first equation says Pe is the ratio of Advective to Convective transport rates, but the written explanation does not say the same thing. The explanation describes it as a ratio of advective to diffusive transport. As a Chemical Engineer, we generally do not use the term "advective" and instead refer to transport by bulk flow as "convective" flow. Thus the definition of Peclet # as the ratio of convective flow to diffusive flow describes it better. In any case, if it is more broadly acceptable to call bulk transport "advective", one still need to change the denominator in the primary equation to conductive or diffusive flow - it cannot be the ratio of advective to convective. Convective in the denominator is incorrect. Thanks — Preceding unsigned comment added by 70.192.76.224 (talk) 19:55, 7 May 2013 (UTC)