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Thursday, 7 December 2017

CLASSIFICATION OF FLUIDS IN FLUID MECHANICS

We were discussing the basic definition and significance of fluid mechanics, kinematic viscosity, Dynamic viscosity and various properties of fluids in our previous post. 

Now we will understand here the various types of fluids with respective examples with the help of this post.

Types of fluids

Fluids are basically classified in to the following seven types as mentioned here
1. Ideal fluid
2. Real fluid
3. Newtonian fluid
4. Non-Newtonian fluid
5. Ideal Plastic fluid
6. Incompressible fluid
7. Compressible fluid

Ideal fluid

Ideal fluid is basically defined as a fluid which will be incompressible and in which viscosity will be zero. 

If we talk practically, there will be no existence of ideal fluid and therefore ideal fluid is an imaginary fluid only.

Real Fluid

Real fluid is basically defined as a fluid which will be incompressible and in which viscosity will not be zero. There will be viscosity in such fluids.

Example:
Water, Kerosene, Petrol, Air

Newtonian fluid

Newtonian fluid is basically defined as a fluid in which shear stress will be directly proportional with the velocity gradient.

We can also say that a fluid which follows the Newton’s law of viscosity will be termed as Newtonian fluid.
Example:
Water, Air, Benzine etc

Non- Newtonian fluid

Non- Newtonian fluid is basically defined as a fluid in which shear stress will not be directly proportional with the rate of shear strain or velocity gradient.

We can also say that a fluid which does not follow the Newton’s law of viscosity will be termed as Non- Newtonian fluid.
Example:
Plaster, Flubber, Slurries and Pastes etc.

Ideal Plastic fluid

Ideal Plastic fluid is basically defined as a fluid in which shear stress will be more than the yield value and shear stress will be directly proportional with the rate of shear strain or velocity gradient.

Incompressible fluid

If density of a fluid will not be changed with change in external pressure or force, then that fluid will be termed as Incompressible fluid.

Liquids will be considered as incompressible fluid. Therefore, hydraulic accumulators are used to develop the nature of compressibility in hydraulic systems.

Compressible fluid

If density of a fluid will be changed with change in external pressure or force, then that fluid will be termed as compressible fluid.

Gases will be considered as compressible fluid.

We will now discuss Newton’s law of viscosity in the category of fluid mechanics in our next post.

Do you have suggestions? Please write in comment box.

Reference:

Fluid mechanics by Y. Nakayama and R F Boucher
Image Courtesy: Google

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