FLUIDS

Ideal fluid:

A fluid, which is incompressible and having no viscosity, is known as an ideal fluid. Ideal fluid is only an imaginary fluid as all the fluids, which exist, have some viscosity.

Real fluid:

A fluid, which possesses viscosity, is known as real fluid. All the fluids, in actual practice, are real fluids.

Example : Water, Air etc.

Newtonian fluid:

A real fluid, in which shear stress in directly proportional to the rate of shear strain or velocity gradient, is known as a Newtonian fluid.

Example : Water, Benzine etc

.

Non Newtonian fluid:

A real fluid, in which shear stress in not directly proportional to the rate of shear strain or velocity gradient, is known as a Non Newtonian fluid.

Example : Plaster, Slurries, Pastes etc. 

Ideal plastic fluid:

A fluid, in which shear stress is more than the yield value and shear stress is proportional to the rate of shear strain or velocity gradient, is known as ideal plastic fluid.

Incompressible fluid:

A fluid, in which the density of fluid does not change which change in external force or pressure, is known as incompressible fluid. All liquid are considered in this category.

Compressible fluid:

A fluid, in which the density of fluid changes while change in external force or pressure, is known as compressible fluid. All gases are considered in this category.

Graphical representation of different fluids

CLASSIFICATION OF FLOWS ON THE BASIS OF MACH NUMBER.

1. Incompressible flow-M less than 0.3
2. Compressible subsonic flow-M between 0.3 and 1
3. Transonic flow-M ranging between values less than 1 and more than 1
4. Supersonic flow-M greater than 1 but less than 5
5. Hypersonic flow - M greater than 5

Types of fluid	Density	Viscosity
Ideal fluid	Constant	Zero
Real fluid	Variable	Non zero
Newtonian fluid	Constant/ Variable	T = u(du/dy)
Non Newtonian fluid	Constant/ Variable	T ≠ u(du/dy)
Incompressible fluid	Constant	Non zero/zero
Compressible fluid	Variable	Non zero/zero