Fluid Motion Control

A fluid is a substance that does not permanently resist distortion.

- Rupam Dutta, Tribeni Deka , Bednidhi Sharma

A fluid is a substance that does not permanently resist distortion. An attempt to change the shape of a mass of fluid results in layers of fluid sliding over one another until a new shape is attained. The branch of engineering that deals with the behavior of fluids (liquids, gases, vapors) is called fluid mechanics. It has several sub disciplines, including aerodynamics and hydrodynamics.

Different types of fluids 

Incompressible fluid: Its density changes only slightly with moderate changes in temperature and pressure. Liquids are generally considered as incompressible.

Compressible fluid: If the changes in density are significant, the fluid is said to be compressible.

Ideal fluid: An incompressible fluid having no viscosity is known as an ideal fluid. It is only an imaginary fluid.

Real fluid: Fluid which possesses viscosity is known as real fluid. All the fluid in practical are real fluids.

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

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

Ideal plastic fluid: A fluid in which shear stress is directly proportional to the rate of shear strain or velocity gradient, is known as ideal plastic fluid.