Newtonian fluids
- Fluids which obey
Newton’s law of viscosity is called Newtonian fluids.
- For Newtonian fluids the ratio of shear stress to the rate of shear or shear rate is constant (τ =μ du / dr)
- A plot of shear stress vs
shear rate or velocity gradient gives a straight line
- In Newtonian fluids, the
viscosity is independent of the rate of shear or shear rate
- Example:- All gases, air, liquids,
such as kerosene, alcohol, glycerine, benzene, hexane-ether, etc,
solutions of inorganic salts and of sugar in water
Non-Newtonian fluids
- Fluids which do not obey
Newton’s law of viscosity is called Non-Newtonian fluids.
- For Non-Newtonian fluids, the ratio of shear stress to the rate of shear or shear rate is not constant
but is considered as a function f rate of shear (τ # μ du / dr)
- A plot of shear stress vs shear
rate or velocity gradient does not give a straight line
- In Newtonian fluids, the
viscosity varies with shear rate
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