Fluid Mechanics (Part-3) (General Engineering) (SSC JE)

Forced vortex is a rotational flow field in which the fluid rotates as a solid body with a constant angular velocity ω, and the streamlines form a set of concentric circles, because the fluid in a forced vortex rotates like a rigid body, the forced vortex is also called flywheel vortex.

Cavitation is a phenomenon in which the static pressure of the liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapour filled cavities in the liquid.

If the density of fluid does not change during its flow, the liquid is said to be incompressible. If the density of fluid changes due to flow of fluid, this type of flow is known as compressible liquid.

Viscosity is defined as the property of a fluid which offers resistance to the movement of one layer of fluid over another adjacent layer of the fluid.

Surface tension depends on intermolecular forces. As temperature increases, molecules of liquid become more active and they move more rapidly, therefore, the intermolecular forces are more instable. Surface tension decrease with increasing temperature.

Incompressible–A fluid in which the density of the fluid does not change during flowing is called as incompressible fluid flow otherwise compressible fluid flow.

Uniform flow–It is defined as the flow in which the velocity at any given time does not change with respect to space.

Cavitation– Cavitation begins to appear in centrifugal pumps when the pressure at the suction falls below the vapour pressure of the liquid.
• The intensity of cavitation increases with the decrease in value of NPSH.
• To avoid cavitation, the suction pressure should be high.

Bourdon gauges–A mechanical gauge used to measure gauge pressure of both liquid and gas. It is invented in France by Mr. Eugene Bourdon.