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B.TECH DEGREE ( CHEMICAL ENGINEERING) ( 5th SEMESTER)

FLUID MECHANICS (CH333)

Time : 3 hrs. Max. Marks : 100

PART - A ( 10 X 2 = 20 Marks)

1. When do you prefer an inclined manometer ?

2. A vaccum gage reads 10 in. Hg when the atmospheric pressure is 30 in. Hg. Assuming the density of

mercury to be 13 . 595 kg / m3 , determine the pressure in Pascal.

3. Define the following dimensionless numbers:

(i) Weber number (ii) Froude Number, (iii) EulersNumber

4. Explain geometric similarity, kinematic similarity and dynamic similarity.

5. Distinguish between Laminar and turbulent flow.

6. Distinguish between kinetic energy correction factor and momentum correction factor.

7. Define sphericity factor.

8. Water is flowing in two different pipes of diameters d and D . Sketch the friction factor vs Reynolds

Number for the two cases.

9. Define hydraulic radius and equivalent diameter.

10. Why is there a negative sign in the pressureheight relation?

PART - B ( 5 X 16 = 80 Marks)

11. The density of a sample of cement is found to be 3100 kg/m3. 25.4 gm of this cement is packed into

a column of diameter = 2.50 cm to form a bed of 27.3 cm thick. When a pressure drop of 12.5 cm of Hg

is established across the bed, it is found that 774 secs. are required to drive 250 c m3 of air through the

bed.

Calculate the average diameter of particles in the cement (assuming spherical) and the surface area per

gram of cement.

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Data : air = 1.83 X 10-5 kg / msec2 ?Hg = 1.355 X 104 kg/m3

g = 9.81 m/sec2

12. (a) A uniform film of oil 0.13mm thick separates two dics, each of 200mm diameter, mounted

coaxially. Ignoring edge effects, calculate the torque necessary to rotate one disc relative to other at a

speed of 7 revolutions/sec., if the oil has viscosity of 0.14 Pascalsec.

(OR)

(b) Compute the atmospheric pressure at elevation 6000m, for the two cases listed below. Considering

the atmosphere as a static fluid.

Case (i) Constant temperature between sea level and 6000m and

Case (ii) air temperature decreasing linearly with elevation at a standard rate of

0.0065 c/m.

Data : At sea level T = 15c P = 100 KN/m2v = 12.03 N/m3

13. (a) Bring out the importance of the relation between the shear stress and velocity

gradient in characterizing the behaviour of flowing fluids.

(b) Water at room temperature flows through a smooth straight pipe A of internal diameter 4cm at an

average velocity of 42 cm/sec. Oil flows through another pipe B of internal diameter 12.5 cm at such a

velocity that dynamic similarity exists between the two streams. Calculate the velocity through pipe B.

(Specific Gravity of oil = 0.85, viscosity of oil = 2 cp and viscosity of water = 1 cp.)

(OR)

(c ) Derive Bernoullis equation for flow througha straight pipe.

(d ) Explain the significance of each term in the above equation

14. (a) Derive Hagen Poisuille equation for pressure drop in laminar flow.

(OR)

The power required by an agitator in a tank is a function of the following four Variables : (a) diameter of

the impeller, (b) RPM of the impeller, (c ) viscosity of liquid, (d) density of liquid and acceleration due to

gravity (g)

From the dimensional analysis, obtain a relation between power and the variables. The power of

consumption is found, experimentally, to be proportional to the square of the speed of rotation.

15. (a) A two dimensional fluid motion is specified in the Legrandian manner by the equation x = x0 ekt ,

y = y0 e-kt

(1) find the path of fluid particle

(2) the expression for velocity in the Eulerian form

(3) state whether the motion is steady and

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(4) whether it is kinematically possible for an incompressible fluid

(OR)

(b) For the velocity profile u= umax ( Ir/rw) 1/n compute the kinetic energy correction factor and

momentum correction factor. What are the values when n = 7?

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PM 305 FLUID MECHANICS

Time : Three hours Maximum : 100 marks

Answer ALL questions.

PART A (10 ? 2 = 20 marks)

1. Distinguish between Newtonian and Nonnewtonian fluids.

2. Define : (a) Path line and (b) Stream line.

3. What is a pitot tube? Sketch a standard pitot tube.

4. What do you mean by Coutte flow?

5. State various minor losses that occur in pipe flow.

6. Define Reynolds number.

7. What are the uses of Vane pump?

8. Distinguish between fixed and variable displacement motors.

9. What are the functions of relief valves in fluid power control systems?

10. State the importance of balancing valves in power actuating systems.

PART B (5 ? 16 = 80 marks)

11. (i) Explain the phenomenon of capillarity. (6)

(ii) Find the capillary rise in a tube of 5 mm diameter, when immersed in(1) water and (2) in mercury. The temperature of water and mercury is 20C and the surface tension of

water and mercury at 20C in contact with air are 0.07358 N/m and 0.51 N/m and the density of water

and mercury at 20C are 998 kg/m3 and 13550 kg/m3. The contact angle for water is 0 and for mercury

is 130. (10)

12. (a) Derive Eulers equation of motion acting along a stream line. Obtain Bernoullis equation by its

integration. List all assumptions made. (16)

Or

(b) (i) Sketch the development of velocity profile for laminar flow through a pipe. (3)

(ii) Crude oil is flowing through a pipe of 50 mm diameter with a velocity of 1.5 m/sec. A pressure

difference of 180 N/mm2 was recorded from two pressure gauges 8 m apart. Find the viscosity offlowing oil. Use HagenPoiseuille Law. (13)

13. (a) (i) Distinguish between laminar and turbulent flow through a pipe. (2)

(ii) An oil flows through a 20 cm diameter pipe at the rate of

75 litres/sec. Find the head lost due to friction for a 500 m length pipe. Take 4f = 0.01874. Also calculate

the power required to maintain this flow. Use Darajs formula. (14)

Or

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(b) Show that the power P developed in a water turbine can be expressed as

where D and B are the diameter and width of the runner, N is the speed in rpm, H is the operating head,

and are coefficient of dynamic viscosity and mass density of the fluid. (16)

14. (a) What is an axial piston pump? Sketch and explain. How does this differ from radial piston pump?

(16)

Or

(b) What is a power pack? Explain different types of power packs used in fluid power control

applications. (16)

15. (a) Discuss with neat sketches, construction and operation of pressure reducing valves. (16)

Or

(b) Write brief notes on : (16)

Flow control and pressure control valves.