Talk:Viscous stress tensor

Epsilon or varepsilon?
This article started from a section in another page which used "$$\epsilon$$" for the viscous stress tensor. However other articles seem to use other symbols, such as "$$\varepsilon$$" or "$$\sigma^\text{v}$$. Should I change it?  To what? --Jorge Stolfi (talk) 15:07, 23 January 2013 (UTC)


 * The best is to use what is common in the literature, or what is used in a very notable reference, and make it consistent all over Wikepedia. I would be in favor of whatever Landau and Lifshitz use. Do you have a copy? PAR (talk) 15:32, 23 January 2013 (UTC)


 * Well, I disagree about "let's make it consistent all over Wikipedia". That goal is about as sensible as trying to make all streets in the country line up in a single great square pattern. Even within a narrow topic, the active editors will hardly be aware of each other's existence; you will never get them all to agree on a common notation. The occasional expert contributors too will rarely have the time to read Wikiproject blogs and style rules; and we do not want them to waste time on form rather than substance. Pages "owned" by one Wikiproject will necessarily link to pages "owned" by other projects, who have their own, incompatible standards. And so on. Moreover, I don't think that consistency of notation across articles is important for readers, either. Whatever notation we choose, 90% of the readers will be using a different one, and will have to translate it anyway. Also, most readers will be looking for a very specific topic, not for a broad overview of a discipline; and therefore will hardly notice that each article uses a different notation. So, instead of wasting time on that goal of dubious merit and certain failure, I believe we should concentrate on editing one or two articles at a time, and making each one reasonably clean, self-contained, narrowly focused, and consistent with itself.  Let each author choose the notation he prefers, as long as he achieves those modest goals. (One merit of splitting off specialized sections, rather than lumping everything into a few jumbo-size articles, is precisely that it makes it easier to achieve those goals.) Yawn, I must go home now. Please forgive me for this rant. Goodnight, and all the best, --Jorge Stolfi (talk) 02:28, 26 January 2013 (UTC)
 * It might be helpful to make a table or at least a sentence that describes the different types of notation out there. I can't tell if the T in my book is the same as the e on this webpage.

162.196.90.91 (talk) 03:26, 18 October 2018 (UTC)

Clearly, getting authors to use a consistent set of notations requires an editor, which Wikipedia seems dead-set against, so some confusion and consternation must result. Yet a better job can be done if authors explain notations, point out alternatives and define operators. For example, lambda, zeta and even kappa are used for the volume or second Lamé coefficient in many texts and other wiki articles. A number of texts and Wolfram Mathematica use eta for shear viscosity instead of mu... I could go on for hours on this because Wiki-Physics is a tower of babble. A self-learner uninterested in getting a grade from a particular professor is poorly served by articles like this. Yes, I can interpret conflicting notations after I know a subject well but I spend days creating tables of alternatives for symbols and expressions (tensors, bra-ket, Gibbs, linear...) in order to understand what authors are trying to say. Yet, I must say this is one of the better articles and I encourage its authors to plow onwards... just ask yourselves, "With whom am I intending to communicate?" Shokutaku (talk) 23:35, 28 August 2019 (UTC)

Factor 2 is missing!
The viscous stress tensor is twice the strain rate tensor, multiplied by the dynamical (shear) viscosity mu. Here, a factor 2 is clearly missing, making the viscous stress erroneous. One can also rather write the viscous stress tensor as mu times Del(v)+transpose(Del(v)) 93.30.106.75 (talk) 10:11, 3 May 2023 (UTC)

nu is not defined
The viscosity coefficient μ is a property of a Newtonian material that, by definition, does not depend otherwise on v or σ. 93.30.106.75 (talk) 10:14, 3 May 2023 (UTC)