Behaviour of Viscosity-Viscous Force

It is easier to move in a liquid with a low viscosity than a liquid with high viscosity. Viscosity is the density of the liquid. More density makes it difficult for objects to go through it, making it a more viscous liquid. Less density makes things go through it quickly, thus making it a liquid of less viscosity. It occurs from friction or the interaction between fluid molecules. For example, oil is thick; therefore, it has a high viscosity; water, on the other hand, is not thick and its viscosity is “thin”. After reading this article, you will know about viscous Force, Newton’s law of viscosity, viscous Force and much more.

Types of viscosity

There are four types of viscosity.

• Extensional viscosity: This type of viscosity reflects the non-Newtonian actions when applied to tensile strength. The relation between the deformation speed and stress occurs in the axial, shaft or biaxial. 

• Kinematic viscosity: We get kinematic viscosity when dynamic viscosity is divided by the fluid’s density and by maintaining the temperature of both viscosities. “V” is the symbol used to represent it; it is noticed under Newtonian force.

• Apparent viscosity: apparent viscosity is defined as viscosity that changes with shear stress.

• Dynamic viscosity: dynamic viscosity is defined as the force needed by any liquid to overcome its internal molecular friction, so the liquid flows.

Viscous force

Viscous force is the force per unit volume that occurs due to tangential stress’s action in the viscous fluid moving. It means the resistance force that a fluid offers when acted upon by some tangential force to its surface. When fluid moves on a surface, fluid molecules adjacent to the surface stick to it, the relative velocity of the fluid being zero concerning the surface. 

Viscous forces arise because of the cohesive forces present in the fluid. When exerted upon by an unbalanced force, fluid layers get dragged. There is a drag by the layer on the downward layer due to attraction forces. This part of the article will answer your question of

What is the Viscous Force? 

The viscous force formula that is applied is

• F=ηA*dv/dx

• η= coefficient of viscosity.

• dv/dx = velocity gradient along x-direction.

• A= Area of the surface of the fluid

Newton’s Law For viscosity

Newton’s law for viscosity explains the relation between the shear rate of the fluid in use and the shear stress. It relates the shear stress(in fluid flow)  to the velocity gradient in a perpendicular path to the fluid’s flow. Shear stress to shear rate ratio is constant, defined as the coefficient of viscosity or viscosity. Newtonian fluids follow Newton’s law. Non-Newtonian fluids do not follow Newton’s law. The viscosity of these Non-Newtonian fluids is not constant and relies on the shear rate.

Application of viscosity

• Arteries and veins circulating blood are dependent upon the fluid’s viscosity.

• Liquids with high viscosity are used as brake oils and are also used to damp some instruments’ motion.

• Liquids with high viscous coefficients are used as lubricants for machinery. To use a suitable lubricant tone needs to know its viscosity and how it differs with temperature because, with a temperature rise, the liquid’s viscosity increases too and vice versa. Knowing viscosity will also help select oils that are low in viscosity used in car engines. Viscosity is the most important characteristic in lubrication and it is also very important in greases; viscosity is the movement resistance.

• Understanding the viscosity of organic fluids helps determine the molecular weights of these liquids.

• Medicines made by drug companies, such as syrup for cough, are made of syrup with high viscosity.

• Varnishes and paints viscosity is controlled closely to be used and applied smoothly without any effort.

• Gum is commonly used and is highly viscous to make it more sticky; viscosity also plays a significant role in preparing food. Cooking oil loses its viscosity when heated and tends to become more viscous when left to cool.

Conclusion

So now you know why knowing viscosity is important and you also got to know its applications in our day-to-day life. Gathering the information on material viscosity will help the producers predict how a product behaves in the environment in which it is put. Knowing the viscosity of a product is very important; for example, knowing the viscosity of toothpaste helps you to pump out the toothpaste as required; if you didn’t know its viscosity, it would be too difficult to pump it out or it would pump out way too much than required.