Shear rate

Shear rate is the rate at which a shear is applied.

imple Shear

Shear rate is defined using the following equation:

dot gamma = frac { u} {h}

Where:

*gamma = The shear rate, measured in reciprocal seconds
* u = The velocity, measured in metres per second
*h = The distance between the two parallel faces that are experiencing the shear.

Or,dot gamma_{ij}=frac {partial v_i} {partial x_j} + frac{partial v_j} {partial x_i}

For the simple shear case, it is just a gradient of velocity in a flowing material. The SI unit of measurement for shear rate is sec-1, expressed as "reciprocal seconds" or "inverse seconds."Cite web
title = Brookfield Engineering - Glossary section on Viscosity Terms
accessdate = 2007-06-10
url = http://www.brookfieldengineering.com/education/viscosity_glossary.asp
]

For a Newtonian fluid wall Shear stress ( au_{w}) can be related to shear rate by au_{w} = {dot gamma_{x} mu}, where mu is the Viscosity of the fluid. For Non-Newtonian fluids, there are different constitutive laws depending on the fluid, which relates the stress tensor to the shear rate tensor.

References


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