Question #130090

1. What is a Newtonian fluid? Is water a Newtonian fluid?

2. How does viscousities of (a) liquids and (b) gases vary with

temperature?

2. How does viscousities of (a) liquids and (b) gases vary with

temperature?

Expert's answer

- Newtonian liquid is a liquid that is characterized by a linear connection between shear stress and velocity gradient. This makes velocity to be distributed as following:

Aspect ratio between shear stress and velocity gradient is viscosity. Newtonian liquid is a ideal model. In real life it is hard to find truly Newtonian liquids. In most cases, water with a good accuracy can be considered as a Newtonian liquid.

2. (a) liquids: "\\mu = A e^{\\frac{B}{T}}" , A,B = const.

(b) gases: from elementary calculations using kinetic theory of gases "\\mu \\propto T^{1\/2}"

from more precise theory (Chapman–Enskog theory): "\\mu = \\mu_0 (\\frac{T}{T_0})^{3\/2} \\frac{T_0+C}{T+C}"

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