Types of Fluids
Fluids are classified into the following types
Ideal fluid: A fluid said to be ideal if it is both incompressible and have no viscosity. Its bulk modulus is infinite. It has no surface tension. Such fluid is only imaginary and does not exist in nature.
Real fluid: A fluid that possesses viscosity, finite compressibility and surface tension.
Newtonian fluid: A real fluid that obeys the Newton’s law of viscosity. In this type of fluid shear stress is directly proportional to shear strain (or velocity gradient).
- For the Newtonian fluid coefficient of viscosity remain constant.
Ideal plastic fluid: A fluid in which shear stress must overcome a yield value and then shear stress is directly proportional to the rate of shear strain.
Types of non-Newtonian fluids
Time independent: (i) Dilatant fluid (ii) Bingham fluid (iii) Pseudoplastic fluid
Time-dependent: (i) Thixotropic fluid (ii) Rheopectic fluid
n > 1, B = 0
Also called shear thickening fluid
Eg. Quicksand, Butter
n = 1, B ≠ 0
Act like solid by withstanding a certain amount of stress without a change in strain.
Eg. Toothpaste, water suspension of clay, jellies
n < 1, B = 0
Eg. Paint, slurry, blood, milk
n < 1, B is a function of time, B = f(t)
Viscosity increases with time.
Eg. Enamels, printer ink
n > 1, B = f(t)
Viscosity decreases with time.
Eg. Gypsum solution
- Types of fluid flow
- Flow Lines - Pathlines, Streamlines, Streaklines, Timelines, Stream Tube