Some of the important properties of the fluid are: density or mass density of the fluid, specific weight or weight density of the fluid, specific volume of the fluid, specific gravity or relative density of the fluid, viscosity of the fluid and others. All these are discussed in this two-part series
3) Specific Volume of the fluid
The specific volume of the fluid is defined as the volume of the fluid occupied by the unit mass of the fluid. Specific volume can also be defined as the volume per unit mass of the fluid.
Specific volume of the fluid is reciprocal of the density of the fluid so its unit of measurement in SI system is m3/kg. This term is important for the gases.
4) Specific gravity of the fluid
Specific gravity of the fluid is defined as the ratio of the density of the fluid to the density of the standard fluid. For the liquids the standard fluid is water and for the gases the standard fluid is air. Specific gravity is also called as relative density. Since specific density is the ration of the two densities, it is a dimensionless quantity and has not unit of measurement. It is denoted by symbol S.
Viscosity of the Fluid
The fluids like water or oil, flow on the surface in the form of layers with the top layer moving at the fastest speed and the bottom layer moving at slow speed. This shows that as we move from the top layer to the bottom layer the speed of the flow of fluid reduces. There is some sort of resistance to the flow of various layers of the fluid, which is offered by the adjoining layers, this property of the fluids is called as viscosity of the fluid.
The viscosity of the fluid is defined as the property of the fluids that offers resistance to the movement of one layer of the fluid over another adjacent layer of the fluid.
In the figure various layers of the liquid are shown. There will be viscous forces between various layers that will resist the movement of the adjoining layers. Let us consider the two layers separated by small distance dy. If the velocity of the lower layer is u, the velocity of the layer just above it will be u+du, where du is the small incremental velocity. This is because the velocity of the upper layer of the fluid is more than the velocity of the lower layers of the fluid.
The SI unit of measurement of viscosity of the fluid is Ns/m2.
Reference
Book: Fluid Mechanics and Hydraulic Machines by Dr. R. K. Bansal
Fluid Mechanics, Applications and Properties of Fluids
This is the series of articles on fluids that describes important concepts of fluids like what is fluid, what is fluid mechanics, applications of fluids, properties of fluids etc. Some important properties of fluids are mass density, specific weight, specific volume, specific gravity, viscosity etc.