Talk:Newtonian fluid

message: This article doesn't work at all for me, anymore. I keep getting errors, i.e.: "
A simple equation to describe Newtonian fluid behaviour is
    Failed to parse (Can't write to or create math output directory): \tau=\mu\frac{dv}{dx}
where
    Failed to parse (Can't write to or create math output directory): \tau
" Sim 03:15, 1 September 2006 (UTC)
replies: text: The current form is fine for i \ne j, but that does need to be noted or replaced with \tau_{ij}=\mu\left(\frac{\partial v_i}{\partial x_j}+\frac{\partial v_j}{\partial x_i} \right)- \left ( p_m + \frac{2}{3}\mu\nabla\cdot\overline{v}\right)\delta_{ij} —kotepho 2006-03-19 22:54Z
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The article currently starts with: "A Newtonian fluid (named for Isaac Newton) is a fluid that flows like water".
I find this confusing because:
1. it's not clear in what way it's supposed to flow like water, and:
2. water is not a newtonian fluid - for large stress it reacts like a solid (i.e. when an asteroid hits water, it shatters as the hydrogen bonds have no time to realign), and for small stresses there are miniscus forces (so a jesus lizard can walk on water) so the stress/rate of strain curve is not linear and doesn't go through the origin.
Also, it's not clear to me if the 'rate of strain', and the velocity gradiant  that appears in the equation are the same thing.
I hope someone who considers himself qualified will rewrite the definition.
88.153.104.131 20:27, 22 July 2007 (UTC)
thread_title: Untitled

message: For a Newtonian fluid, the viscosity, by definition, depends only on temperature and pressure (and also the chemical composition of the fluid if the fluid is not a pure substance), not on the forces acting upon it.
Suggested rewrite:
By definition the viscosity of a Newtonian fluid does not depend on the forces acting upon it.  For a given pure chemical substances the viscosity depends only on pressure and temperature. For a mixture the viscosity also depends on the chemical composition.  —Preceding unsigned comment added by 130.86.76.10 (talk) 21:46, 26 May 2009 (UTC)
thread_title:  This section needs rewording? 

message: When I was in elementary school my science teacher mentioned "Newtonian fluids" to the class, claiming that they had both solid and liquid characteristics and holding up Silly Putty as an example. Now that I'm all grown up I realized that she was actually referring to non-Newtonian fluids. Stonemason89 (talk) 16:58, 17 June 2010 (UTC)
thread_title: Term is often incorrectly used

message: The statement "Water and air are examples of (practically) Newtonian fluids, which include , and exhibit the Weissenberg effect" is contradictory because the Weissenberg effect is exhibited by non-Newtonian fluids. It should be removed.Skater00 (talk) 21:35, 6 March 2013 (UTC)
replies: text: Indeed, that was probably an editing accident, sorry. Someone already fixed it. --Jorge Stolfi (talk) 05:45, 13 March 2013 (UTC)
thread_title:  Contradictory statement 

message: My professors and books always explained me that the strain of a newtonian fluid is defined as follows:
:\tau=-\mu\frac{du}{dy}
Shouldn't we add a minus to this formula?  — Preceding unsigned comment added by 145.94.226.124 (talk) 10:06, 14 December 2016 (UTC)
thread_title:  Minus?