Concepts: The fluids which obey Newton’s Law of viscosity i.e. shear stress is directly proportional to velocity gradient are called
Newtonian Fluids. Examples are: Water, air, Petrol, Kerosene, and Mercury.
Mathematical relation between shear stress and rate of deformation in Newtonian fluids are expressed as: τ=μ The fluids which do not follow Newton’s law of viscosity are called
Non- Newtonian fluids. They have nonlinear shear-stress Vs deformation-rate relationship.
The mathematical model for describing the behavior of non-Newtonian fluids is the
Power-Law model, which is given as:
τ=μ For n < 1; these fluids called
Pseudoplastic fluids. Example: blood, milk.
For n > 1; these fluids called
dilatants fluids. Examples are Sugar in water, rice starch solution.
The hypothetical fluids having a zero viscosity ( μ = 0) is called an
ideal fluid and the resulting motion is called an
ideal or inviscid flow.