SPSC 2014 Assistant Engineer (Civil) BPS-17, Public Health Engineering Department (2014) — Hydraulics & Fluid Mechanics Paper

Assistant Engineer (Civil) BPS-17, Public Health Engineering Department (2014) — Hydraulics & Fluid Mechanics. Competitive examination for the post of Assistant Engineer (Civil) BPS-17 in PHED, Government of Sindh · Thursday 23 January 2014, 2:00 pm to 5:00 pm · Max marks 100. Attempt any five questions.

1. 1(a) Discuss Density, Specific weight and Specific volume of a fluid. Derive the relationship between (i) Specific weight and Density (ii) Density and Specific volume. (10) (b) Describe surface tension. If the pressure difference between the inside and outside of an air bubble of diameter 0.01 mm is 25.2 kPa, what will be the surface tension at the air-water interface? (10)

2. 2(a) Describe the working mechanism of a Reciprocating Pump. (08) (b) Give classification of Turbines and discuss how a suitable type of turbine is selected under the existing conditions and requirements. (12)

3. 3(a) Describe Hydraulic coefficients for an orifice and find out the relationship between them. (10) (b) A circular tank of diameter 2.75 m contains water up to a height of 5 m. The tank is provided with an orifice of diameter 38 cm at the bottom. Find the time taken by water to fall from 5 to 3.2 m. Also compute the time of emptying the tank. (10)

4. 4(a) Give characteristics of Compound, Parallel and Equivalent pipes. (09) (b) A power of 125 kW is to be transmitted through a 2.6 km long pipeline having a pressure of 3900 kN/m² at the inlet. If the pressure drop over the entire length of pipe is 790 kN/m² and the coefficient of friction of the pipe is 0.0059, find the diameter of the pipe and efficiency of transmission. (11)

5. 5(a) What is Buoyancy and Center of Buoyancy? Also describe stability of floating bodies. (08) (b) On a flat plate of size 2 m × 1 m, experiments were conducted in a wind tunnel with a wind speed of 50 km/hr. The plate is kept at such an angle that the coefficients of drag and lift are 0.8 and 0.9 respectively. Determine (i) Drag force (ii) Lift force (iii) Resultant force and (iv) Power exerted by the air stream on the plate. Take density of air = 1.15 kg/m³. (12)

6. 6(a) What is fluid mechanics? Differentiate between solids, gases and liquids. (10) (b) State Pascal's law and mention its application in engineering and technology. (10)

7. 7A wall having dimensions of 5 m in vertical and 100 m in width is erected across a stream. The water level on the up- and downstream of the wall is 4 and 2 m respectively; find (a) the total pressure on the wall, and (b) the position of center of pressure from the water surface. (20)

8. 8An aqueduct having a discharge of 100 cusecs fills up a certain tank of volume 720000 ft³. The water flows through the aqueduct at its maximum permissible velocity of 3 ft/sec. Find: (a) how many hours would be required to fill up the tank, (b) what is the cross sectional area of the aqueduct, and (c) what is the pressure per unit area on the bottom of the tank? (20)