2007 Anna University B.E Mechanical CE 253-FLUID MECHANICS AND MACHINERY

[ganeshbala]

B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2003.

Third Semester

Mechanical Engineering

[blink]CE 253 — FLUID MECHANICS AND MACHINERY[/blink]

(Common to Mechatronics Engineering)

Time : Three hours Maximum : 100 marks

Answer ALL questions.  PART A — (10 ? 2 = 20 marks)

1. What is a real fluid? Give examples.

2. Find the height through which water rises by capillary action in a 2 mm bore if surface tension at the prevailing temperature is 0.075 g/cm.

3. When is the flow regarded as unsteady? Give an example for unsteady flow.

4. Define the following terms (a) Source and Sink (b) Doublet.

5. A 20 cm diameter pipe 30 km long transport oil from a tanker to the shore at 0.01 m3/s. Find the Reynolds number to classify the flow. Take viscosity
= 0.1 Nm/s2 and density = 900 kg/m3 for oil.

6. What is boundary layer? Give a sketch of a boundary–layer region over a flat plate.

7. Give the dimensions of the following physical quantities :

(a) Pressure
(b) Surface tension
(c) Dynamic viscosity
(d) Kinematic viscosity.

8. What is a Mach number? Mention its field of use.

9. What are reaction turbines? Give examples.

10. What are rotary pumps? Give examples.

PART B — (5 ? 16 = 80 marks)
11. Show for a perfect gas the bulk modulus for a elasticity equals its pressure for (i) An isothermen process (ii) times the pressure for an isentropic process.

12. (a) Derive the continuity equation of differential form. Discuss whether the equation is valid for a steady or unsteady flow, viscous or inviscid flow, compressible or incompressible flow.

Or

(b) (i) Does a velocity given by represent possible fluid motion of an incompressible fluid. (4)
(ii) Two components of velocity in an incompressible fluid flow are given by and Determine the third component, assuming that the origin is a stagnation point. (4)
(iii) The velocity in flow field is given by
u = 3 m/s v = 6 m/s
Determine the equation of the streamline passing through the origin and the one passing through the point (2m, 3m). (8 )

13. (a) Derive an expression for Darcy–Weisbach formula to determine the head loss due to friction. Give the expression for relation between friction factor 'f' and Reynolds's number 'Re' for laminar and turbulent flow.

Or

(b) A 30 cm diameter pipe of length 30 cm is connected in series to a 20 cm diameter pipe of length 20 cm to convey discharge. Determine the equivalent length of pipe of diameter 25 cm, assuming that the Friction factor remains the same and the minor losses are negligible.

14. (a) Consider force F acting on the propeller of an aircraft, which depends upon the variable U, , D and N. Derive the non–dimensional functional form

Or

(b) A Pelton turbine is required to develop 9000 KW when working under a head of 300 m the impeller may rotate at 500 rpm. Assuming a jet ratio of 10 and an overall efficiency of 85% calculate
(i) Quantity of water required
(ii) Diameter of the wheel
(iii) Number of jets
(iv) Number and size of the bucket vanes on the runner.

15. (a) Draw a neat sketch of a reciprocating pumps. List the components and briefly explain their functions.

Or

(b) A radial flow impeller has a diameter 25 cm and width 7.5 cm at exit. It delivers 120 liters of water per second against a head of 24 m at
1440 rpm. Assuming the vanes block the flow area by 5 percent and hydraulic efficiency of 0.8, estimate the vane angle at exit. Also calculate the torque exerted on the driving shaft if the mechanical efficiency is
95 percent.