Types of Fluid
- Newtonian Fluid
- Non-Newtonian Fluid
Non- Newtonian Fluids and Types
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 that depend on the type of fluid and condition of flow.
The Non-Newtonian Fluids are further categorized as-
- Dilatant Fluids
- Bingham Plastic Fluids
- Pseudoplastic Fluids
- Thixotropic Fluids
- Rheopectic Fluids
Non-Newtonian Fluids Conditions
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
- 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