Which is the fluid whose viscosity does NOT change with the rate of deformation?

Explanation:

Newtonian fluids: fluids for which the shear stress is linearly proportional to the shear strain rate and follow Newton's law of viscosity.

• \(\tau = \mu \frac{{du}}{{dy}}\) where μ is shear viscosity of the fluid
• Newtonian fluids are analogous to elastic solids (Hooke’s law: stress proportional to strain)
• Any common fluids, such as air and other gases, water, kerosene, gasoline, and other oil-based liquids, are Newtonian fluids
• A fluid whose viscosity does not change with the rate of deformation or shear strain is known as a Newtonian fluid.

Non-Newtonian fluid: fluids for which the shear stress is not linearly related to the shear strain rate are called non-Newtonian fluids 

• In non-Newtonian, the viscosity is dependent on the shear rate (Shear Thinning or Thickening)
• examples include slurries and colloidal suspensions, polymer solutions, blood, paste, and cake batter

Ideal fluid: fluids which don’t have viscosity and are incompressible are termed as an ideal fluid

• The ideal fluid does not offer shear resistance i.e no resistance is encountered as the fluid moves.

Real fluid: Fluids which do possess viscosity are termed as real fluids.

These fluids always offer shear resistance i.e. Certain amount of resistance is always offered by these fluids as they move.