Properties of Fluids

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properties of fluids


Understanding the properties of fluids is essential to analyze their behavior in working conditions.
In this article, we have covered the fluid properties namely mass density, specific weight, specific volume, specific gravity, viscosity, vapor pressure, compressibility and surface tension.

Mass Density:

Mass Density (ρ) is the property of a fluid that is the mass per unit volume.

Specific Weight:

Specific Weight (w) of a fluid is the weight per unit volume.

Specific Volume:

Specific Volume (v) of a fluid is the volume of the fluid per unit mass.

Specific Gravity or Relative Density:

Specific Gravity (s) of a fluid is the ratio of the mass density of a fluid to the mass density of a standard fluid.


Viscosity is the property by virtue of which it offers resistance to the movement of one layer of fluid over the adjacent layer.

Vapor Pressure:

When a liquid is confined in a closed vessel, the ejected vapor molecules accumulated in the space between free liquid pressure and top of the vessel exert a partial pressure on the liquid surface. This pressure in the liquid is known as vapor pressure.


The normal compressive stress of any fluid element at rest is known as hydrostatic pressure which arises as a result of innumerable molecular collisions in the entire fluid. The degree of compressibility of a substance is characterized by bulk modulus of elasticity (B).

Surface Tension:

Surface tension is a measure of the fluid tendency to take a spherical shape, caused by the mutual attraction of the liquid molecules.

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