### 4HE Fluid Mechanics April-1996

Part A (20 X 2 = 40 marks)

1. An ideal fluid is an incompressible and __________ fluid.
2. For a Newtonian fluid shear stress is directly proportional to __________.
3. Kinematic viscosity of a liquid is dynamic viscosity divided by its __________.
4. In M, L, T system of dimension, Power is represented as __________.
5. Weber number is ratio of inertial force to __________ force.
6. For incompressible fluid, continuity equation in integral form is Q = __________.
7. In flow net equipotential lines are orthogonal with __________.
8. Relative roughness of a pipe surface is its absolute roughness divided by its __________.
9. In laminar flow through pipe as Reynolds number increases the friction coefficient __________.
10. Pitot -Static tube measures __________ pressure.
11. Turbulent velocity fluctuations in a flow is measured by __________ meter.
12. For a solid sphere falling under gravity at terminal settling velocity in a fluid the buoyant force is equal to __________.
13. Pressure drag on a body is due to the formation of __________.
14. Ergun's equation relates __________.
15. Reciprocating pumps are suitable for high pressure rise and __________ discharge.
16. An example of Positive displacement pump is __________.
17. In a centrifugal pump as head increases discharge __________.
18. Power required by a fan is proportional to the discharge, pressure rise and __________.
19. Pump suitable for corrosive liquid is __________.
20. Fans have __________ pressure rise than blowers.
21. Part B (5 X 12 = 60 marks)

UNIT - I

22. a) Explain the following terms
1. Vapor pressure
2. Bulk modulus

b) State the Pascal's law of pressure at a point.

c) What are the desirable properties of manometric fluid.

Or

23. a) A soap bubble 50 mm in diameter contains a pressure (in excess of atmospheric) of 2 bar. Find the surface tension in the soap film.

b) If a 1 m diameter pipe carrying air at a velocity of 3.8 m/s is to be modelled for dynamic similarity by a water pipe of diameter 10 cm, what would be the velocity of water.

(Data to be given:rair = 1.16 kg/m3; mair = 1.81 x 10-5 kg/m.sec;
velocity of water = 2.435 m/sec )

UNIT - II

24. a) Check whether the following function is a valid potential function
25. f = A(x2 - y2)

(Yes; the given is a valid potential function)

b) A siphon consisting of a 3 cm diameter tube is used to drain water from a tank. The outlet end of the tube is 2 m below the water surface in the tank. Neglecting friction, calculate the discharge. If the peak point of the siphon is 1.4 m above the water surface in the tank, estimate the pressure of fluid at the point of siphon.

(15.94 m3/hr; 67.96 kPa abs )

Or

26. a) Distinguish between Laminar and Turbulent flow with example
27. b) Distinguish between subsonic flow and supersonic flow

c) Explain the term "Boundary Layer" and friction drag.

UNIT - III

28. a) Explain the working principle of a Hot wire anemometer.
29. b) Water flows through a Venturi meter which has a diameter at the inlet of 1.2 m and a diameter of 0.6 m at the throat. The difference in pressure between the main and the throat is measured by a differential mercury gauge, which shows a deflection of 5.1 cm. Find the discharge through the meter and also calculate the velocity of water at the throat. Take the coefficient of discharge of the meter as 0.98.

(1.016 m3/sec; 3.594 m/sec)

Or

30. a) Compare the merits and demerits of Orifice meter and Venturi meter in the measurement of flow.
31. b) A 75o triangular notch is discharging under submerged conditions. The vertex of the notch is at a height of 30 cm from the channel bed. The elevation of water surfaces upstream and downstream of the notch, measured from the channel bed are 75 cm and 50 cm respectively. Assuming Cd = 0.6, estimate the discharge over the notch.

UNIT - IV

32. A water softener consists of a vertical tube 50 mm diameter and packed to a height of 0.5 m with ion-exchange resin particle. The particles may be considered as sphere with a dia of 1.25 mm. Water flows over the bed, because of gravity as well as pressure difference, at a rate of 300 cc/s. The bed has a porosity of 0.3. Calculate the pressure drop.
33. (5.519 Bar)

Or

34. Derive an expression for minimum fluidization velocity. Also give its physical significance.
35. UNIT - V

36. Explain the working principle of an Air-lift pump with a neat sketch. What are its merits and demerits over conventional centrifugal pump.
37. Or

38. Explain the various pump characteristics and indicate the shut-off head and design point.