B.E./B.Tech. DEGREE EXAMINATION,
Third Semester
Civil Engineering
CE 233 — FLUID MECHANICS
Time : Three hours Maximum : 100 marks
Answer ALL questions.
PART A — (10 ? 2 = 20 marks)
1. Distinguish between ideal and real fluids.
2. Express 3 m of water head in cm of mercury and pressure in KPa.
3. List out the properties of a velocity potential function.
4. Can the path line and a streamline cross each other at right angles? Why?
5. Why is it necessary to assume that the flow is steady before integrating Euler’s equation to derive Bernoulli’s equation?
6. What is the meaning of the term momentum flux? What are its units?
7. What is meant by the term ‘‘Piezometric head’’?
8. A pipe has D = 40 cm, L = 100 m, f = 0.005. Compute the length of an equivalent pipe which has D = 20 cm and f = 0.008.
9. State three demerits of a distorted model.
10. Define momentum thickness.
PART B — (5 ? 16 = 80 marks)
11. A trapezoidal plate of top width 5 m, bottom width 4 m and height 3 m is immersed vertically in water with its parallel sides parallel to the water level and its top edge at a depth of 2 m below the water level. Find the water thrust on one side of the plate and the depth of center of pressure.
12. (a) A mercury U–tube monometer shown in the fig. is used to measure the pressure above atmospheric of water in a pipe, the water being in contact with the mercury in the left–hand limb.
(i) Explain its action.
(ii) If the mercury is 30 cm below A in the left–hand limb and 20 cm
above A in the right–hand limb, what may be gauge pressure at A?
Specific gravity of mercury is = 13.6.
(iii) If the pressure at A is reduced by 40 kN/m2 what will be the new
difference in level of the mercury?

Or
(b) List out the various methods of construction of flow nets and Explain the graphical method in detail.
13. (a) Derive Euler’s equations for a three–dimensional fluid flow.
Or
(b) A jet propelled boat moves at 32 km/hr in a fresh water lake. There are two jets each of diameter 20 cm. The absolute velocity of the discharged jets is 25 km/hr. Calculate the pump discharge, force of propulsion, power input and efficiency of propulsion if the inlet orifices are located at amid–ships and in bow.
14. (a) Two reservoirs whose water surface elevations differ by 12 m are connected by the following horizontal compound pipe system starting from the high level reservoir. = 200 m, = 0.2 m, and
= 500 m, = 0.3 m, = 0.006. Considering all head losses and assuming that all changes of section are abrupt, compute the discharge through the system. Determine the equivalent length of a 0.25 m diameter pipe if minor losses are neglected and friction factors are assumed to be the same. Sketch HGL and TEL.
Or
(b) Water flows through a 10 cm diameter, 30 m long pipe at a rate of
1400 lpm. What percent of head would be gained by replacing the central one third length of pipe by another pipe of 20 cm diameter. Assume that the changes in section are abrupt and f = 0.008 for all pipes. Neglect entrance and exit losses but consider all other losses.
15. (a) Using Buckingham’s ??theorem, show that the drag of a supersonic aircraft is given by :
.
Where = Reynolds number, = Mach number,
? = fluid density, V = velocity of aircraft, c = sonic velocity =
K = bulk modulus of fluid, L = chord length, = wing area =
chord x span, ? = a functional notation.
Or
(b) It is desired to obtain the dynamic similarity between a 30 cm diameter pipe carrying linseed oil at 0.5 m3/s and a 5 m diameter pipe carrying water. What should be the rate of flow of water in lps? If the pressure loss in the model is 196 N/m2, what is the pressure loss in the prototype pipe? Kinematic viscosities of linseed oil and water are 0.457 and 0.0113 stokes respectively. Specific gravity of linseed oil = 0.82.