# JNTU Previous Exam papers Civil B Tech 3rd Year Fluid Mechanics November 2008

**JNTU, B.Tech,I-Semester, FLUID MECHANICS , November 2008**

**(Civil Engineering)**

**SET-3**

1. (a) The space between two parallel plates is filled with oil, each side of the plate

being 720mm. The thickness of the oil film is 1.5mm. The upper plate, which moves at 3m/s requires a force of 120N to maintain the speed. Determine dynamic and Kinematic viscosity of oil if specific gravity of oil is 0.95.

(b) A vertical cylinder of diameter 180 mm rotates concentrically inside another

cylinder of diameter 181.2 mm. Both the cylinders are 300 mm high. The

space between the cylinders is filled with a liquid whose dynamic viscosity is

unknown. Determine dynamic viscosity if a torque of 20 N-m is required to

rotate the inner cylinder at 120 rpm.

2. A plane surface of negligible thickness is immersed in a static liquid at an inclination

of ? with the free surface. Determine the expressions for the total hydrostatic thrust

on one side of the plane surface and also for the centre of pressure.

3. (a) The velocity of a 3-D flow field is given by V = (y2+z2)i + (x2+z2)j + (x2+y2)k

Determine the acceleration components at a point (1,2,3)

(b) Derive the continuity equation for a 3-D fluid flow.

4. (a) A pipe line, 600 mm diameter carrying oil of sp.gr. 0.85 at the flow rate of 1800 lit/s has a 900 bend in the horizontal plane. The pressure at the entrance to the bend is 1.471 bar and loss of head in the bend is 2 m of oil. Find the

magnitude and direction of the force exerted by the oil on the bend and show

the direction of the force on a sketch of the bend.

(b) At a point in the pipe line where diameter is 20 cm, the velocity of water is

4 m/s and the pressure is 343 kN/m2. At a point 15 cm downstream, the

diameter reduces to 10cm. Calculate the pressure at this point, if the pipe is

vertical with flow downward. Neglect the losses.

5. (a) Differentiate between

i. Stream line body and bluff body

ii. Friction drag and pressure drag.

(b) A kite 60cm x 60cm weighing 2.943 N assumes an angle of 10o to the horizontal.

If the pull on the string is 29.43N when the wind is flowing at a speed of 40 km/hr. Find the corresponding coefficient of drag and lift. Density of air is given as 1.25 kg/m3.

6. (a) Describe Reynold’s experiment with a neat sketch. What are the outcomes of Reynolds experiment.

(b) A crude oil of viscosity 0.97 poise and relative density 0.9 is flowing through

a horizontal circular pipe of diameter 10cm and of length 10m. Calculate the difference of pressure at the two ends of the pipe, if 100 kg of the oil is collected in a tank in 30 seconds.

7. The population of a city is 8X105 and it is to be supplied with water from a reservoir 6.4 km away. Water is to be supplied at the rate of 0.14m3 per head per day and half the supply is to be delivered in 8 hours. The full supply level of the reservoir is R.L 180.00. and its lowest water level is R.L.105.00. The delivery end of the main is at R.L 22.50 and the head required there is 12m. Find the diameter of the pipe. Take f= 0.04.

8. A venturimeter having inlet diameter 100 mm and throat diameter 25 mm is fitted

in a vertical pipe, throat is 0.3 m below the inlet, for measuring the flow of petrol of specific gravity 0.78. Pressure gauges are fitted at inlet and throat. Taking loss of head between inlet and throat as 36 times the velocity head at inlet, find cd of the meter and the discharge when the inlet gauge reads 274.68 KN/m2.