March 9, 2010

CE 261 — FLUID MECHANICS Question Papers

B.E./B.Tech. DEGREE EXAMINATION,
Third Semester
Electrical and Electronics Engineering
CE 261 — FLUID MECHANICS
Question Papers

Time : Three hours Maximum : 100 marks
PART A — (10 ? 2 = 20 marks)
1. What is the difference between cohesion and adhesion?
2. State the Newton's law of viscosity.
3. Define temporal acceleration.
4. State Bernoulli's theorem and mention the assumptions involved in it.
5. State the basic principle behind the theory of venturimeter.
6. Enlist the minor losses in flow through pipes.
7. Distinguish between laminar and turbulent flows.
8. How is specific speed of turbine defined?
9. State the basic principle of centrifugal pumps.
10. What are the uses of characteristic curves?

PART B — (5 ? 16 = 80 marks)
11. (i) A two–dimensional flow field is given by determine :
(1) the stream function (4)
(2) the velocity at L (2, 6) and M (6, 6) and the pressure difference between the points L and M (3)
(3) the discharge between the streamlines passing through the points L and M. (3)
(ii) In a pipe of diameter 200 mm and length 500 m, an oil of specific gravity 0.9 and viscosity 0.06 poise is flowing at the rate of 0.06 m3/s. Find :
(1) the head lost due to friction, and (3)
(2) power required to maintain the flow. (3)
Take f = 0.0791/(Re)1/4.
12. (a) Inside a 60 mm diameter cylinder a piston of 59 mm diameter rotates concentrically. Both the cylinder and piston are 80 mm long. If the space between the cylinder and piston is filled with oil of viscosity of 0.3 N.s/m2 and a torque of 1.5 Nm is applied, find :
(i) the r.p.m. of the piston, and
(ii) the power required. (16)
Or
(b) The dynamic viscosity of an oil, used for lubricating between a shaft and sleeve is 15 poise. The shaft rotates at 200 r.p.m. The power lost in the bearing for a sleeve length of one meter is 500 watts. The diameter of the sleeve is 250.15 mm. Calculate the diameter of the shaft and the thickness of the oil film. (16)
13. (a) A pipe line carrying oil of specific gravity 0.87 changes in diameter from 200 mm diameter at position ‘1’ to 500 mm diameter at position ‘2’ which is 4 meters at a higher level. If the pressures at 1 and 2 are 100 kN/m2 and 60 kN/m2 respectively and the discharge is 0.2 m3/s, determine :
(ii) Direction of flow. (16)
Or
(b) (i) Derive an expression to find the loss of head due to friction in pipes.
(12)
(ii) Define stream line and path line. (4)
14. (a) A reaction turbine works at 450 r.p.m. under a head of 120 m. Its diameter at inlet is 1.2 m and the flow area is 0.4 m2. The angles made by absolute and relative velocities at inlet are 20? and 60? respectively with the tangential velocity. Determine :
(i) the volume rate of flow,
(ii) the power developed, and
(iii) the hydraulic efficiency. (16)
Or
(b) The impeller of a centrifugal pump having external and internal diameters 500 mm and 250 mm respectively, width at outlet 50 mm and running at 1200 r.p.m. works against a head of 48 m. The velocity of flow through the impeller is constant and equal to 3.0 m/s. The vanes are set back at an angle of 40? at outlet. Determine :
(i) Inlet vane angle
(ii) Work done by the impeller on water per second, and
(iii) Manometric efficiency. (16)
15. (a) Derive an expression to find the discharge through an orifice meter. (16)
Or
(b) (i) The rate of flow of water through a horizontal pipe is 0.25 m3/s. The diameter of the pipe which is 20 cm is suddenly enlarged to 40 cm. The pressure intensity in the smaller pipe is 11.772 N/cm2. Determine the loss of head due to sudden enlargement and pressure intensity in the large pipe. (12)
(ii) Co–efficient of discharge of venturimeter is always greater than orificemeter. Why? (4)