Question Set 106

1. What is fluid ? What is fluid mechanics ?

Answer : A fluid is a substance which always responses to shear stress and doesn’t have any definite shape. It may or may not have any definite volume.

2. How to determine the characteristics of fluid flow ?

Answer: By the values of Reynolds Number.

3. What are laminar and turbulent flows ?

Answer : When a fluid is flowing around an object or flowing through an object, the flow may be smooth or may be distorted. The smoother flow occurs due to low velocity and distorted flow occurs due to high velocity. This low velocity smoother flow is called laminar flow and distorted flow is called turbulent flow.

4. What is buoyancy force ?

Answer : Buoyancy is the upward force which is felt on an object simply immersed into a fluid.

5. Which dimensionless number is used to determine the speed of aircraft ?

Answer : Mach Number.

6. What are compressible and incompressible flows ?

Answer : compressible flow – variable density fluid flow .

Incompressible flow – fixed density fluid flow .

7. What is meant by compressibility property of fluid ?

Answer : Compressibility is the property of those fluids which doesn’t have any fixed density.

8. What is meant by flow property of fluid ?

Answer : Flow property means the responsiveness of the fluid to the shear stress.

9. What is meant by no-slip condition in fluids ?

Answer : No-slip condition occurs at the microscopic level where the fluid is flowing on a solid surface and the velocity of the fluid is zero at the contact surface .

10. What are the different units of viscosity ?

Answer : In SI – Kg (m.s) . In CGS slug (ft.s) . The values of viscosity is often very small so for that reason a more reasonable unit is used which is called cP or centipoise.