Ideal fluid

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Fluid:

A fluid is a gas or liquid that, unlike a solid, flows to assume the shape of the container in which it is placed. This occurs because a fluid responds to a shear stress, or a force per unit area directed along the face of a cube of fluid, by flowing, rather than by an elastic displacement as in a solid.

PROPERTIES OF FLUID

1.DENSITY:

Density of a fluid is defined as the ratio of the mass of a fluid to its volume.

2.SPECIFIC VOLUME:

Specific volume of a fluid is defined as the volume of a fluid occupied by a unit mass or volume per unit mass of a fluid.

3.VISCOSITY OF LIQUID:

Viscosity is defined as the property of a fluid which offers resistance to the movement of one layer of fluid over another adjacent layer of fluid.

TYPES OF FLUIDS BASED ON VISCOSITY:

The fluids may be classified into following five types:

1. Ideal fluid
2. Real fluid
3. Newtonian fluid
4. Non-Newtonian fluid
5. Ideal plastic fluid

Ideal fluid

An ideal fluid is a fluid that has several properties including the fact that it is:

 • Incompressible – the density is constant
 • Irrotational – the flow is smooth, no turbulence
 • Nonviscous –(Inviscid) fluid has no internal friction ( η = 0)

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Ideal fluid do not actually exist in nature, but sometimes used for fluid flow problems.

2.Real fluid: Fluid that have viscosity(μ > 0) and their motion known as viscous flow.

All the fluids in actual practice are real fluids.

Fluid dynamics:

we use ideal fluid in 2 equations :

1.Continuity equation

2.Bernoulli equation

3. Newtonian Fluids:

A real fluid in which the shear stress is directly proportional to rate of shear strain (or velocity gradient).

4. Non-Newtonian Fluid:

A real fluid in which the shear stress is not proportional to the rate of shear strain.

5. 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).