FLUID MECHANICS UNIT - I

FLUID MECHANICS UNIT - I 

1. Define density or mass density. 

Density of a fluid is defined as the ratio of the mass of a fluid to its volume.

Its unit is Kg/m3 .

2. Define specific gravity or relative density. 

Specific gravity is defined as the ratio of the weight density of a fluid to the weight density of a standard of a standard fluid.. for liqids, the standard fluid is taken as water and for gases , the standard fluid is taken as air.

3. Define specific volume. 

Specific volume of a fluid is defined as the volume of a fluid occupied by a unit mass or volume per unit mass of a fluid.

It is expressed as m3 /Kg.

4. Define specific weight or weight density. 

Specific weight or weight density of a fluid is defined as the ratio between the weight of a fluid to its volume.

It is denoted by ω. ω = ρg

5. Define compressibility. 

Compressibilty is the reciprocal of bulk modulus of elasticity K, which is defined as the ratio of compressine to volumetric strain.

6. Define coefficient of compressibility.

 Coefficient of compressibility is denoted by β and defined as volumetric strain per unit compressive stress.

7. Define surface tension of fluids. 

The surface tension of a fluid is the property which enables the fluid to resist tensile stress. It is due to the cohesion between the molecules at the surface of a liquid.

8. What is meant by capillarity. 

Capillarity is defined as the phenomenon of rise or fall of a liquid surface in a small tube relative to the adjacent level of liquid, when the tube is dipped vertically in the liquid.

Its unit is metre.

9. What is meant by capillary rise and capillary depression.

The rise of liquid surface in the capillary tube is known as capillary rise and the fall of liquid surface in the capillary tube is known as capillary depression.


10. What is known as viscosity. 

The property of a fluid whidh offers resistance to the movement of one layer of fluid over adjacent layers of fluids is called viscosity. 10

11. What is meant by kinematic viscosity? 

The ratio between the dynamic viscosity and density is defined as kinematic viscosity of a fluid.

12. State ‘Newton’s law of viscosity. 

It states that ‘For a steady uniform flow, the shear stress on a fluid element is layer is directly proportional to the rate of shear strain. The constant of proportionality is called the coefficient of viscosity.

13. State Pascal’s law.

Pascal’s law states that the pressure or intensity of pressure at a point in a static fluid is equal in all directions.

14. Define Newtonian and Non-Nwtonian fluids.

 A real fluid in which the shear stress is proportional to the rate of shear strain is known as Newtonian fluid. Fluids which donot obey Newton’s law of viscosity are called Non-Newtonian fluids.

15. State Bernoulli’s equation.

 In a steady flow of frictionless and incompressible fluid flow system, the total energy per unit weight of flowing fluid remains constant.

16. What is known as Euler’s equation of motion.

If the flow is assumed to be ideal viscous force and it is zero then the equation of motion is known as Euler’s equation of motion.

17. Mention hydraulic devices using Bernoulli’s equation. 

1. Venturimeter 2. Orificemeter 3. Pitot tube

18. What is a flow net?

 The graphical pattern obtained by the intersection of stream lines and equipotential lines are known as flow net.

19. Define Stream line. 

Stream line is said to be an imaginary line drawn through a flow field such that the tangent at each point on the line indicates the direction of the velocity of the fluid particle at that point.

20. What are manometers? 

Manometars are defined as the devices used for measuring the pressure at a point in afluid by balancing the column of fluid by the same or another column of the fluid.