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Definition of Viscosity

Definition of Viscosity –

What is Viscosity ?

Viscosity is defined as the internal friction of a flowing fluid. Viscosity may also be defined as its internal resistance to gradual deformation through shear stress or tensile stress. Viscosity is different for different fluids and will be described below with an example. The viscosity may be high or low depending on the type of liquid and type of gas.

When a cup filled with water is taken and poured into a pan, the water completely moves into the pan leaving only a few drops of water inside the cup. When the same cup is filled with light oil and poured into the pan, it moves slower than water leaving some amount of oil in the cup. When we fill the same cup with honey and poured into a pan, it moves very slowly. The differences that can be seen among water, oil and honey is only due to the viscosity. Viscosity is different for different fluids and can be increased or decreased. A fluid which has no resistance to shear stress is called as Ideal Fluid or Inviscid Fluid.

Zero Viscosity can be observed in many fluids and they are named as Super Fluids. Almost all the fluids have some viscosity  and are known to be viscous fluids or viscid fluids.

Temperature and Pressure are the two main and basic factors affecting the viscosity. When the temperature increases, the viscosity of a fluid automatically decreases and when the temperature decreases, the viscosity of the fluid increases. When the pressure increases along the side of the flow of the fluid, the flow of fluid increases and when the pressure decreases, the flow of fluid increases.

The details about Dynamic Viscosity, Kinematic Viscosity and related content to the viscosity will be described in the next posts.

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