Types of Fluid

Fig.- Types of Fluids

Non- Newtonian Fluids

These types of fluids do not obey Newton’s Law of viscosity. The relation between Shear Stress and Velocity gradient is given by the following formula-

τ = A (du/dy)n + B

Here A and B are constants which depend on the type of fluid and condition of flow.

Conditions for different Non-Newtonian Fluids

For Dilatant Fluids

  • n > 1; and B = 0
  • Ex- Butter, Quicksand

For Bingham Plastic Fluids

  • n = 1; and B ≠ 0
  • These fluids always have certain minimum shear stress before yielding.
  • Ex- toothpaste, gel, sewage sludge etc.

For Pseudoplastic Fluids 

  • n < 1 ; and B = 0
  • Ex- Paints, Blood, Paper pulp, Lipsticks, Rubber solution etc.

For Thixotropic Fluids

  • n < 1; and B ≠ 0
  • Viscosity increases with time.
  • Ex- Enamel, Printers Ink etc.

For Rheopectic Fluids

    • Viscosity decreases with time.
    • Ex- Gypsum solution in water, etc.

Compressibility (β), Isothermal Bulk Modulus (kT) and Adiabatic Bulk Modulus

Compressibility (β)

  • It is the inverse of Bulk Modulus of Elasticity.

β = 1/k = -dv/(v × dp)

v = volume

Isothermal Bulk Modulus (kT)

kT = Pfinal = Ρrt

Adiabatic Bulk Modulus

ka = ϒ × Pfinal

ϒ = Cp/Cv