Newtonian and Non-Newtonian Fluids

Newtonian fluid named after the scientist Isaac Newton, is a fluid that stress opposed to strain rate curve is linear and passes by the origin. And the steady proportionality is referred to as the viscosity. For instance this equation will give better understanding of Newtonian fluid behavior:

Here t is the shear stress exerted by the fluid, u is the fluid viscosity and the final thing is the velocity gradient perpendicular to the direction of shear, or equivalently the strain rate.

Generally Newtonian fluid means which keeps on flowing, regardless of the forces acting on it. For instance water is said to be Newtonian, since it continues to exemplify fluid properties no matter how fast it is stirred or mixed. A Newtonian fluid, the viscosity depends only on temperature and pressure and not on the forces acting upon it.

Comparison with that of Newtonian

A non-Newtonian fluid differs in any of the way from those of Newtonian fluids through flow properties. Notably the viscosity of non-Newtonian fluids is not free of shear rate or shear rate history. Though, there are some non-Newtonian fluids with shear-independent viscosity that nonetheless exhibit normal stress-differences or other non-Newtonian behavior. Most of the salt solutions and molten polymers are non-Newtonian fluids, as are many commonly found substances like ketch up, custard, toothpaste, starch suspensions, paint, and blood so on.

These Newtonian and non-Newtonian fluids can be best studied through several rheological properties which relate stress and strain rate tensors under many different flow conditions like the oscillatory shear, or extensional flow which are measured using different devices or rheometers. And these properties are better studied using tensor-valued constitutive equations that are known in the field of continuum mechanics.

The usage of the principle

Newtonian fluid in contrast to the non-Newtonian fluid stirring will leave a hole, or climb the stirring rod since the shear thinning the drop in viscosity causing it to flow more. The shear thickening is also used in all wheel drive systems utilizing a viscous coupling unit for power transmission. A known example of the opposite, a shear thinning fluid, or pseudo plastic fluid, is paint: one wishes the paint to flow readily off the brush when it is being applied to the surface being painted, but not to trickle extremely.

Thus both Newtonian and non-Newtonian fluids play crucial role in many of the applications and the latter exceeds the previous by formula and practicality to apply through new mechanisms.

Questions:

• What are Newtonian and non-Newtonian fluids?
• State the significance of the types of fluids.