1.8 Types of fluids based on viscosity

There are five types of fluids in fluids mechanics

1. Ideal Fluid
2. Real Fluid
3. Ideal Plastic Fluid
4. Newtonian Fluid
5. Non-Newtonian Fluid

1.Ideal Fluid

A Fluid which has an ideal flow and which is incompressible is called as ideal fluid. Ideal fluids are assumed to have zero viscosity.
It should be noted that in practice there is no ideal fluid. 

2. Real Fluid

A fluid which doesn't have ideal flow and which is compressible is called as real fluid. Real Fluids have viscosity and they face friction while they are flowing. 
All the fluids in real practice are Real Fluids

3. Ideal Plastic Fluid

A fluid in which shear stress is more than the yield value and the shear stress is directly proportional to the shear strain(du/dy) is called as Ideal Plastic Fluid.
 One of the example of the Ideal Plastic Fluid is Bingham Plastic. 

4. Newtonian Fluid

The Fluid which obeys the newtons law of viscosity is called as Newtonian Fluid. It should be remembered that the Newtons law o viscosity can be given as

And thus the fluid which obeys this law is called as Newtonian fluid.

5. Non Newtonian Fluid

A Fluid which does not obey the above equation(Newtons law of viscosity) is called as Non-Newtonian Fluid. Thus Non Newtonian fluids deviate from the above equation.

References:
http://en.wikipedia.org/wiki/Bingham_plastic
http://www.definition-of.com/Ideal+Plastic+fluid 
http://encyclopedia2.thefreedictionary.com/Ideal+Fluid  
http://mechteacher.com/fluid/