What is a Non-Newtonian fluid?
A non-Newtonian fluid is a fluid that does not follow Newton's law of viscosity, i.e., constant viscosity independent of stress. In non-Newtonian fluids, viscosity can change when under force to either more liquid or more solid. Ketchup, for example, becomes runnier when shaken and is thus a non-Newtonian fluid.
Non-Newtonian fluid shear stress between two fluid layers is may to proportional or may not. This depends on the flow behavior index.
In case of Newtonian Fluid:
- (Shear Stress) ∝ (rate of angular deformation)
- or, (Shear Stress) = (dynamic viscosity)* (rate of angular deformation)
- (Shear Stress) ∝ (rate of angular deformation)^n
- or, (Shear Stress) = (apparent viscosity)*(rate of angular deformation)^n
- Where, n = Flow behavior index [ n = 1 for Newtonian fluid ]
- if n < 1 , the fluid called Pseudo-plastic fluid.
- if n > 1, the fluid is called Diltatant Fluid.
Examples of non-newtonian fluids (found around the house):
- Tomato Sauce / Ketchup
- Corn Starch in water solution
- Golden Syrup / Honey
- Coffee in solution in water
- Motor Oil
- Brake Fluid / Clutch Fluid (Hydraulic Fluids)
- WD40 Lubrication Spray
- Personal Lubricants (X Rated !)
Newtonian behavior of fluids:
The Newtonian behavior of fluids is an assumption to simplify the theoretical analysis.
In reality, no such fluid exist although water can approximate the same.
