fluidmechanics-jntu old question papers

II B.Tech I Semester Regular Examinations, November 2008
FLUID MECHANICS AND HYDRAULIC MACHINERY
( Common to Electrical & Electronic Engineering and Production
Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
1. (a) What is the principle on which a peizometer works? Draw a neat sketch and
explain. What are dierent types of the same?
(b) If the surface tension at the soap air interface is 0.088N/m, Calculate the
internal pressure in a soap bubble of 3 cm diameter. [10+6]
2. (a) What is the criteria to distinguish laminar flow from turbulent flow?
(b) Determine whether the following velocity components satisfy the continuity
equation.
i. u = cx, v = −cy
ii. u = −cx/y, v = c log xy. [6+10]
3. (a) Draw neat sketches of total energy line and hydraulic gradient line for the
following cases and discuss:
i. Uniform diameter parallel pipe line
ii. Parallel converging pipe line
iii. Parallel diverging pipe line.
(b) Two reservoirs are connected by a pipeline consisting of two pipes in series,
one of 15 cm diameter and 6m long and another of 22.5 cm diameter and 15m
long. If the dierence in water levels of the reservoirs is 6m, calculate the
discharge by considering all the losses. Assume f = 0.02 for both the pipes.
[8+8]
4. (a) A jet of water of 86 mm diameter strikes a curved vane at the centre with a
velocity of 30 m/sec. The curved vane is moving with a velocity of 8m/sec in
the direction of the jet. Find the force exerted on the plate in the direction of
the jet, power and eciency of the jet. Assume that the plate is smooth.
(b) Explain, how you find the impact of jet striking an unsymmetrical fixed curved
plate at one of the tips. [8+8]
5. (a) Describe the status of hydroelectric power in India.
(b) Explain how the load factor, capacity factor and utilization factor interrelated.
Also explain the significance of diversity factor. [8+8]
6. (a) In a Pelton wheel the buckets deflect the jet through 1700 and the relative
velocity is reduced by 12% due to bucket friction. For a speed ratio of 0.47,
calculate from first principles the hydraulic eciency of the wheel. The bucket
circle diameter of the wheel is 0.9 m and there is one jet for which Cv = 0.98.
The actual eciency of the wheel is 0.9 times its theoretical eciency. The
wheel develops 1700 kW under a head of 550 m. Calculate:
i. The speed of wheel in r.p.m and
ii. The diameter of the nozzle.
(b) A Francis turbine has to be designed to develop 367.5 kW under a head of H
= 70 m while running at N = 750 r.p.m. Ratio of width of runner to diameter
of runner, n = 0.1, inner diameter is half the outer diameter. Flow ratio =
0.15, hydraulic eciency = 95%, mechanical eciency = 84%. Four percent
of the circumferential area of runner to be occupied by the thickness of vanes,
velocity of flow is constant and the discharge is radial at exit. Calculate:
i. The diameter of the wheel,
ii. The quantity of water supplied, and
iii. The guide vane angle at inlet and runner vane angles at inlet and exit.
[16]
7. (a) Define the terms ‘unit power’, ‘unit speed’ and ‘unit discharge’ with reference
to a hydraulic turbine. Also derive expressions for these terms.
(b) Sketch and describe a modern method of regulation to maintain a constant
speed for either
i. Pelton wheel or
ii. Francis turbine. [8+8]
8. (a) Define indicator diagram. How will you prove that area of indicator diagram
is proportional to the work done by the reciprocating pump?
(b) A centrifugal pump impeller whose external and internal diameters are 400 mm
and 200 mm respectively is running at 950 r.p.m. The rate of flow through the
pump is 0.035 m3/s. the suction and delivery heads are 5 m 25 m respectively.
The diameters of the suction and delivery pipes are 120 mm and 80 mm
respectively. If the outlet vane angle is 450, the flow velocity is constant and
equal to 1.8 m/s and power required to drive the pump is 15 kW, determine:
i. Inlet vane angle
ii. The overall eciency, and
iii. The manometric eciency. [8+8]