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B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2010
Fourth Semester
Civil Engineering
CE2253 - APPLIED HYDRAULIC ENGINEERING
(Regulation 2008)
Time: Three hours Maximum: 100 Marks
Answer ALL Questions
ANNA UNIVERSITY SYLLABUS - Click Here
PART A — (10 × 2 = 20 Marks)
1. Define open-channel flow.
2. Compute the hydraulic mean depth of a small channel 1 m wide, 0.5 m deep with water flowing at 2 m/s.
3. Write down the Chezy’s formula for determining velocity of flow in an open channel.
4. Show that maximization of discharge requires minimization of the wetted perimeter of the channel for a given area of flow.
5. What is a draw down curve?
6. Indicate the usefulness of hydraulic jump.
7. Why is the theoretical suction height of a pump limited?
8. Define negative slip. How it occurs?
9. Classify Pelton turbine according to
(a) The direction of flow through the turbine runner
(b) The action of water on turbine blades.
10. Define specific speed of a turbine.
PART B — (5 × 16 = 80 Marks)
11. (a) (i) Define specific energy. How would you express the specific energy for a wide rectangular channel with depth of flow ‘d’ and velocity of
flow ‘V ’? Draw the typical specific energy diagram and explain its features. (8)
(ii) Calculate the specific energy, critical depth and velocity for the flow of 10 m3/s in a cement lined rectangular channel 2.5 m wide with
2 m depth of water. Is the given flow subcritical or supercritical? (8)
Or
(b) (i) Define Froude number r F . Describe the flow for = 1
r F , < 1
r F and
> 1
r F . Represent a discharge versus depth curve for a constant specific energy and explain its features. (8)
(ii) A trapezoidal channel has a bottom width of 6.1 m and side slopes of 2 H : 1 V. When the depth of flow is 1.07 m, the flow is
10.47 m3/s? What is the specific energy of flow? Is the flow tranquil or rapid? (8)
12. (a) (i) A V-shaped open channel of included angle 90° conveys a discharge of 0.05 m3/s when the depth of flow at the center is 0.225 m.
Assuming that C = 50 m1/2/s in the Chezy’s equation, calculate the slope of the channel. (8)
(ii) Calculate the dimensions of the rectangular cross-section of an open channel which requires minimum area to convey 10 m3/s. The slope
being 1 in 1500. Take the Manning’s ‘n’ as 0.013. (8)
Or
(b) Derive the expressions for the most economical depths of flow of water in terms of the diameter of the channel of circular cross-section:
(i) For maximum velocity and
(ii) For maximum discharge. (16)
13. (a) (i) In a given channel, 0 Y and c Y are two fixed depths if Q , n and 0 S are fixed. Also, there are three possible relations between 0 Y and c Y . Further, there are two cases where 0 Y does not exist. Based on these, how the channels are classified? (5)
(ii) A river 100 m wide and 3 m deep has an average bed slope of 0.0005. Estimate the length of the GVF profile produced by a low
weir which raises the water surface just upstream of it by 1.5 m. Assume n = 0.035. Use direct step method with three steps. (11)
Or
(b) (i) Explain the classification of hydraulic jumps. (5)
(ii) A spillway discharges a flood flow at a rate of 7.75 m3/s per metre width. At the downstream horizontal apron the depth of flow was
found to be 0.5 m. What tailwater depth is needed to form a hydraulic jump? If a jump is formed, find its type, length, head loss and energy loss as a percentage of the initial energy. (11)
14. (a) (i) With the help of neat sketches, explain the features of a volute type and a diffusion type centrifugal pump. (8)
(ii) A centrifugal pump delivers salt water against a net head of 15 m at a speed of 100 rpm. The vanes are curved backward at 30° with
the periphery. Obtain the discharge for an impeller diameter of 30 cm and outlet width of 5 cm at a manometric efficiency of 90%.(8)
Or
(b) (i) Draw the indicator diagram of a reciprocating pump for the following cases :
(1) Without air vessels on both suction and delivery sides.
(2) With air vessel only on suction side. (2 × 4 = 8)
(ii) For a hydraulic machine installed between A and B , the following data is available :
At A At B
Diameter 20 cm 30 cm
Elevation 105 m 100 m
Pressure 100 kPa 200 kPa
The direction of flow is from A to B and the discharge is 200 litres per second. Is the machine a pump or a turbine? (8)
15. (a) (i) Classify the turbines based on:
(1) Action of water on turbine blades.
(2) Head on turbine.
(3) Direction of flow through turbine runner.
(4) Specific Speed.
(5) Disposition of turbines shaft. (5)
(ii) A Pelton turbine is required to develop 9000 kW when working under a head of 300 m. The runner may rotate at 500 rpm.
Assuming the jet ratio as 10, speed ratio as 0.46 and overall efficiency as 85%, determine the following :
(1) Quantity of water required.
(2) Diameter of the wheel.
(3) Number of jets.
(4) Number of buckets. (11)
Or
(b) (i) Draw the characteristic curves of turbines and explain. (5)
(ii) An inward flow reaction turbine operates under a head of 25 m running at 200 rpm. The peripheral velocity of the runner is 20 m/s
and the radial velocity at the runner exit is 5 m/s. If the hydraulic losses are 20% of the available head, calculate:
(1) The guide-vane exit angle.
(2) The runner-vane angle.
(3) The runner diameter.
(4) The specific speed, if the width of the runner at the periphery is 30 cm and
(5) The power produced by the turbine. (11)
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