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Reg. No. :

B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2010Third Semester

Mechanical Engineering

ME 2204 FLUID MECHANICS AND MACHINERY

(Common to Aeronautical Engineering, Automobile Engineering and

Production Engineering)

(Regulation 2008)

Time : Three hours Maximum : 100 Marks

Answer ALL questions

PART A (10 2 = 20 Marks)

1. Suppose the small air bubbles in a glass of tap water may be on the order of50 m in diameter. What is the pressure inside these bubbles?

2. Why is it necessary in winter to use lighter oil for automobiles than insummer? To what property does the term lighter refer?

3. Cite examples for dimensionally homogeneous and non-homogeneousequations.

4. Mention the circumstances which necessitate the use of distorted models.5. What is a laminar sub layer?6. Define eddy viscosity. How it differs from molecular viscosity?7. State the principles on which turbo-machines are based.8. Under what conditions would you suggest use of double-suction pump and a

multistage pump?

9. What is an air vessel? List the objectives that would be fulfilled by the use ofair vessels.

10. What is priming?PART B (5 16 = 80 Marks)

11. (a) (i) A U-tube is made of two capillaries of diameter 1.0 mm and 1.5 mmrespectively. The tube is kept vertically and partially filled with

water of surface tension 0.0736 N/m and zero contact angle.

Calculate the difference in the levels of the menisci caused by the

capillary. (6)

(ii) Lateral stability of a long shaft 150 mm in diameter is obtained by

means of a 250 mm stationary bearing having an internal diameter

of 150.25 mm. If the space between bearing and shaft is filled with

a lubricant having a viscosity 0.245 N s/m2, what power will be

Question Paper Code : 53196

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required to overcome the viscous resistance when the shaft is

rotated at a constant rate of 180 rpm? (10)

Or

(b) (i) A pipeline 60 cm in diameter bifurcates at a Y-junction into two

branches 40 cm and 30 cm in diameter. If the rate of flow in the

main pipe is 1 .5 m3/s, and the mean velocity of flow in the 30 cm

pipe is 7.5 m/s, determine the rate of flow in the 40 cm pipe.

(4)

(ii) Derive the energy equation and state the assumptions made while

deriving the equation. (12)

12. (a) A pipe of 10 cm in diameter and 1000 m long is used to pump oil ofviscosity 8.5 poise and specific gravity 0.92 at the rate of

1200 lit./min. The first 30 m of the pipe is laid along the ground sloping

upwards at 10to the horizontal and remaining pipe is laid on the ground

sloping upwards 15to the horizontal. State whether the flow is laminar

or turbulent? Determine the pressure required to be developed by the

pump and the power required for the driving motor if the pump efficiency

is 60%. Assume suitable data for friction factor, if required.

Or

(b) Two pipes of diameter 40 cm and 20 cm are each 300 m long. When the

pipes are connected in series and discharge through the pipe line is

0.10 m3/sec, find the loss of head incurred. What would be the loss of head

in the system to pass the same total discharge when the pipes are

connected in parallel? Take f = 0.0075 for each pipe.

13. (a) (i) The resisting force F of a plane during flight can be considered asdependent upon the length of aircraft (l), velocity (v), air viscosity

( ), air density ( ) and bulk modulus of air (K). Express the

functional relationship between these variables using dimensional

analysis. Explain the physical significance of the dimensionless

groups arrived. (8)

(ii) A geometrically similar model of an air duct is built to 1/25 scale

and tested with water which is 50 times more viscous and 800 times

denser than air. When tested under dynamically similar conditions,

the pressure drop is 200 kN/m2 in the model. Find the

corresponding pressure drop in the full scale prototype and express

in cm of water. (8)

Or

(b) The drag force (F) on a partially submerged body depends on the relative

velocity (V) between the body and the fluid, characteristic linear

dimension (l), height of surface roughness (k), fluid density ( ), the

viscosity ( ) and the acceleration due to gravity (g). Obtain an

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expression for the drag force, using the method of dimensional analysis.

14. (a) The head discharge characteristics of a centrifugal pump is givenbelow.

Discharge (lit/sec) 0 10 20 30 40 50

Head (meters) 25.3 25.5 24.5 22.2 18.7 12.0

The pump delivers fresh water through a 500 m long, 15 cm diameter

pipe line having friction coefficient of f = 0.025. The static lift is 15 m.

Neglecting minor losses in the pipe flow, find (i) the discharge of the

pump under the above conditions (ii) driving power of the pump motor.

Assume a pump efficiency of 72%.

Or

(b) An inward flow reaction turbine having an overall efficiency of 80% is

required to deliver 136 kW. The head H is 16 m and the peripheral

velocity is 3.3 H . The radial velocity of flow at inlet is 1.1 H . The

runner rotates at 120 rpm. The hydraulic losses in the turbine are 15% of

the flow available energy. Determine (i) diameter of the runner, (ii) guide

vane angle, (iii) the runner blade angle at inlet and (iv) the discharge

through the turbine.

15. (a) Explain the working principle of single and double acting reciprocatingpumps with neat diagram in detail. Also explain the effects of inertia

pressure and friction on the performance of the pump using indicator

diagrams with and without air vessel. (8 + 8)

Or

(b) (i) For a single acting reciprocating pump, piston diameter is 150 mm,

stroke length is 300 mm, rotational speed is 50 r.p.m. The pump is

required to lift water to a height of 18 m. Determine the theoretical

discharge. If the actual discharge is 4.0 lit./sec, and the mechanical

efficiency is 80% determine the volumetric efficiency, slip,

theoretical power and the actual power required. (10)

(ii) Explain the working principle of screw pump and gear pump with

neat diagram in detail. (6)

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