non-Newtonian Fluid

A non-Newtonian fluid is a type of fluid where the viscosity is dependent on the ratio of shear stress to the shear rate. Hence, it is called apparent viscosity $η_{a}$ .
This means that the viscosity is not constant for a given temperature and pressure, and is dependant on flow conditions like geometry, shear rate, type of flow (steady, unsteady etc).
Thus the flow curve of a non-Newtonian fluid is non-linear and does not pass through the origin.

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