Fluid Mechanics (Part-2) (General Engineering) (SSC JE)

Variation of viscosity with temperature–
• Temperature affects the viscosity. The viscosity of liquids decreases with the increase of temperature while the viscosity of gases increases with the increase of temperature.
• This is due to reason that the viscous forcese in a fluid are due to cohesive forces and molecular momentum transfer.
→ Gas possesses no definite volume and is compressible in nature.

When fluid passes through the nozzle, the pressure of the fluid decreases because cross-sectional area decreases and the velocity of the fluid increases. Continuity equation,

Viscosity–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.

• Viscosity of fluid is due to cohesion and interaction between fluid particles.

Ideal fluid–A fluid, which is incompressible and is having no viscosity, is known as an ideal fluid. Ideal fluid is only an imaginary fluid as all the fluids which exist have some viscosity.

In impulse turbine steam expands in nozzles only.
In impulse reaction turbine steam expands in nozzles as well as it passes through blades.