CE2253 Applied Hydraulic Engineering Question Bank for May / June 2013 Exam

Anna University

QUESTION BANK

DEPARTMENT: CIVIL

SEMESTER: IV

CE2253 Applied Hydraulic Engineering

SUBJECT CODE / Name: CE 2253/APPLIED HYDRAULIC ENGINEERING


UNIT – I: OPEN CHANNEL FLOW
PART - A (2 Marks)

1. Distinguish between open channel flow and conduit flow.

2. What are wide channels?

(AUC Nov/Dec 2010) (AUC Nov/Dec 2010)

3. Define open channel flow ? (AUC Apr/May 2010)

4. Compute the hydraulic mean depth of a small channel 1m wide, 0.5m deep with water flowing at m/s. (AUC Apr/May 2010)

5. Define Specific energy of flowing liquid. (AUC Apr/May 2011)

6. How do you find the critical depth of flowing water? (AUC Apr/May 2011)

7. What are the different types of flow in open channel? (AUC Apr/May 2012)

8. Define Specific energy. (AUC Apr/May 2012)

9. Write Renold’s number for different states of flow in an open channel.

10. “Critical flow section is an excellent control section” – Justify the statement.

11. In an open channel of rectangular section if the minimum specific energy is 6 m, what is its critical depth?

12. A rectangular channel carries a flow of 4m3/s/m, what is the critical depth?

13. What are the different types of varied flows?

14. What is an isovel?

15. Define hydraulic depth(D) of an open channel flow.

PART –B (16 Marks)

1. How do you classify open channels? Explain in detail. Also explain the velocity distribution in open channel. (AUC Nov/Dec 2010)

2. Write short notes on the following:

(i) Critical flow and its computations

(ii) Channel Transition (AUC Nov/Dec 2010)

3. (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.

(ii) Calculate the specific energy, critical depth and velocity for the flow of 10m3/s in a cement lined rectangular channel 0.5m wide with 2m depth of water. Is the given flow subcritical or supercritical? (AUC Apr/May 2010)

4. (i) Define Froude number FR. Describe the flow for FR = , FR < and FR >1. Represent a discharge versus depth curve for a constant specific energy and explain its features.

(ii) A trapezoidal channel has a bottom width of 6.1m and side slopes of 2H: 1V. 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? (AUC Apr/May 2010)

5. A trapezoidal channel with side slopes of 2 horizontal: 3 vertical has to carry 20 m3/sec.

Find the slope of the channel when the bottom width of the channel is m and the depth of the water is 3 m. Take Manning’s n = 0.03. (AUC Apr/May 2011)

6. Calculate the specific energy of 12m3/sec of water flowing with a velocity of 1.5 m/s in a rectangular channel 7.5m wide. Find the depth of water in the channel when the specific energy would be minimum. What would be the value of critical velocity as well as minimum specific energy? (AUC Apr/May 2011)

7. (i) How are the flows classified under specific energy concepts?

(ii) A 8m wide channel conveys 15 cumecs of water at a depth of 1.2m. Determine

(1) Specific Energy of the flowing water (2) Critical depth, critical velocity and minimum specific energy (3) Froude number and state whether the flow is subcritical or supercritical. (AUC Apr/May 2012)

8. (i) Explain the salient features of Specific Energy curve.

(ii) Determine the critical depth for a specific energy of 1.5 m in the following channels

(1) Rectangular channel

(2) Triangular channel

(3) Trapezoidal channel. (AUC Apr/May 2012)

9. (i) Find the critical depth for a specific energy of 1.5 m in: (1) Rectangular channel of bottom width 2m (2)Triangular channel of side slope 1:1.5

(3)Trapezoidal channel of bottom width 2m and side slope 1:1? (ii) What are the different types and states of flow in open channel?

10. (i) Prove that for critical flow specific is minimum.

(ii) Calculate the width of a rectangular channel required to carry a discharge 15m3/s as critical flow at a depth of 1.2m.


UNIT – II: UNIFORM FLOW
PART - A (2 Marks)

1. Mention the significance of Manning’s formula. (AUC Nov/Dec 2010)

2. What are the essential conditions for most economical section? (AUC Nov/Dec 2010)

3. Write down the Chezy’s formula for determining velocity of flow in an open channel. (AUC Apr/May 2010)

4. Show that the maximization of discharge requires maximization of the wetted perimeter of the channel for a given area of flow. (AUC Apr/May 2010)

5. Distinguish between uniform and non-uniform. (AUC Apr/May 2011)

6. Define the Froude Number. What is its significance? (AUC Apr/May 2011)

7. Distinguish between normal depth and critical depth. (AUC Apr/May 2012)

8. What are the conditions for the most economical triangular channel section?

(AUC Apr/May 2012)

9. Define ‘conveyance’ of an open channel.

10. Why are best hydraulic sections in open channel flow referred as most economical sections?

11. A river with a lined banks has a Manning’s n = 0.014, and Chezy’ C = 55, What is its hydraulic radius?

12. What is equivalent roughness or composite roughness of an open channel?

13. What are the geometric conditions for a triangular channel to be most economic?

14. Define normal discharge and normal slope.

15. Define uniform flow.

PART –B (16 Marks)

1. A channel is designed to carry a discharge of 20 m3/s with Manning’s n = 0.015 and bed slope of 1 in 1000 (for trapezoidal channel side slope M = 1√3). Find the channel dimensions of the most efficient section if the channel is (i) trapezoidal

(ii) rectangular. (AUC Nov/Dec 2010)

2. Explain the computation of uniform flow using Manning’s and Chezy’s method. (AUC Nov/Dec 2010)

3. (i) A V – shaped open channel of included angle 90º 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.

(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 in 1500. Take the Manning’s ‘N’ as 0.013. (AUC Apr/May 2010)

4. 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. (AUC Apr/May 2010)

5. (i) Derive the Chezy’s equation for steady uniform flow.

(ii) Derive the relationship for most economical trapezoidal channel. (AUC Apr/May 2011)

6. A power canal of trapezoidal section has to be excavated through hard clay at the least cost. Determine the dimensions of the channel given, discharge equal to 14 m3/s, bed slope 1/2500, Manning’s n = 0.02. (AUC Apr/May 2011)

7. (i) Show that the hydraulic radius is half the flow depth for the most economical trapezoidal channel section.

(ii) Determine the most economical section of rectangular channel carrying water at the rate of 0.6 cumecs. The bed slope is 1 in 2000. Assume Chezy’s constant C = 50. (AUC Apr/May 2012)

8. (i) How do you determine velocity of flow in open channel?

(ii)The bed width of a trapezoidal channel section is 40 m and the side slope is 2 horizontal to 1 vertical. The discharge in the canal is 60 cumecs. The Manning’s ‘n’ is 0.015 and the bed slope is 1 in 5000. Determine the normal depth. (AUC Apr/May 2012)

9. Derive the geometrical properties of a most economical triangular channel section.

10. (i) A rectangular channel of width 15m has abed slope of 0.00075 and Manning’s n = 0.016. Compute the normal depth to carry a discharge of 50m3/s?

(ii)Explain the graphical method of determination of normal depth for a trapezoidal channel.


UNIT – III: VARIED FLOW

PART - A (2 Marks)

1. What are the assumptions made in dynamic equation for gradually varied flow?

(AUC Nov/Dec 2010)

2. What is mean by back water curve? (AUC Nov/Dec 2010)

3. What is a draw down curve? (AUC Apr/May 2010)

4. Indicate the usefulness of hydraulic jump. (AUC Apr/May 2010)

5. What is the energy loss in a hydraulic jump? (AUC Apr/May 2011)

6. How is back water curve formed? (AUC Apr/May 2011)

7. Write down the dynamic equation of gradually varied flow. (AUC Apr/May 2012)

8. Distinguish between positive and negative surges. (AUC Apr/May 2012)

9. Differentiate between draw down and back water curves.

10. Define sequent depth.

11. What is the nature of slope of the channel if critical depth line occurs above normal depth line?

12. What is the state of flow after formation of a hydraulic jump?

13. What is the control section of an open channel flow?

14. What are the assumptions in varied flow?

15. Write two methods used for flow profile determination.

PART – B (16 Marks)

1. How do you classify surface profiles? Briefly explain the various salient features of various profiles. Also write a note on hydraulic jump. (AUC Nov/Dec 2010)

2. A 50 m long laboratory flume has a rectangular section with a width of 2m and ends in a free overall. The channel is made of glass and the bed drops by 5 cm in the entire length. At a certain discharge, it was seen that the depth near the channel entrance was more or less constant at 0.5 m. Use the direct step method to obtain the length of profile. Use two equal depth increments. (AUC Nov/Dec 2010)

3. (i) In a given channel, Yo and Yc are two fixed depths if Q, N and So are fixed. Also, there are three possible relation between Yo and Yc. Further, there are two cases where You does not exist. Based on these, how the channels are classified?

(ii)A river 100 m wide and 3m 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. (AUC Apr/May 2010)

4. (i) Explain the classification of hydraulic jumps.

(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 tail water 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. (AUC Apr/May 2010)

5. In a rectangular channel of 0.5 m width, a hydraulic jump occurs at a point where depth of water flow is 0.15 m and Froude number is 0.5. Determine

(i) The specific energy

(ii) The critical and subsequent depths

(iii) Loss of head and

(iv) Energy dissipated. (AUC Apr/May 2011)

6. A river of 45 m wide has a normal depth of flow of 3 m and an average bed slope of in 10,000.A weir is build across the river raising the water surface level at the weir site to 5 m above the bottom of the river. Assuming that the back water curve is an arc of circle; calculate the approximate length of the curve. Manning’s n = 0.025.(AUC Apr/May 2011)

7. (i) What are the assumptions made in the analysis of gradually varied flow?

(ii)The bed width of a rectangular channel is 24 m and the depth of flow is 6m. The discharge in the canal is 86 cumecs. The bed slope of the channel is 1 in 4000. Assume Chezy’s constant C = 60. Determine the slope of the free water surface. (AUC Apr/May 2012)

8. (i)What are the conditions for the formation of hydraulic jump?

(ii)In a rectangular channel of bed width 0.5 m, a hydraulic jump occurs at a point where depth of flow is 0.15 m and Froude’s number is 2.5. Determine

(1) The specific energy (2) The critical depth (3) The subsequent depths (4) Loss of head (5) Energy dissipated. (AUC Apr/May 2012)

9. (i) A rectangular channel carries a flow with a velocity of 0.65m/s and depth of 1.4m. If the discharge is abruptly increased three fold by sudden lifting of a gate on the upstream side, estimate the velocity and height of the resulting surge?

(ii)With neat diagrams explain different types of channel transitions.

10. (i)Write the gradually varied flow equation in an open channel flow. Deduce the equation for a wide rectangular channel using Manning’s and chezy’s equation.

(ii)Explain with a neat diagram the surges produced when (i) a sluice gate is suddenly raised (ii)sluice gate is suddenly lowered.


UNIT – IV: PUMPS
PART - A (2 Marks)

1. Define Priming. (AUC Nov/Dec 2010)

2. What is the significance of air vessel? (AUC Nov/Dec 2010)

3. Why is the theoretical suction height of a pump limited? (AUC Apr/May 2010)

4. Define negative slip. How it occurs? (AUC Apr/May 2010)

5. What are the differences between jet pump and submersible pump?

(AUC Apr/May 2011)

6. Draw an ideal indicator diagram. (AUC Apr/May 2011)

7. Define specific speed of a pump. (AUC Apr/May 2012)

8. Draw the indicator diagram for a single acting reciprocating pump.

2012)Why submersible pump named so?

9. Differentiate between a rotodynamic pump and rotary pump.

10. What is the function of foot valve in a pump?

(AUC Apr/May

11. What is the condition for finding the minimum starting speed of centrifugal pump?

12. Name two rotary pumps.

13. What are multistage pumps?

14. For a single acting reciprocating pump what are the angles at which there is no flow into and out of the air vessel?

PART –B (16 Marks)

1. A single acting reciprocating pump having a cylinder diameter of 150 mm and stroke of 300 mm is used to raise the water through a height of 20 m. Its crank rotates at 60 rpm. Find the theoretical power required to run the pump and the theoretical discharge. If actual discharge is 5 lit/s find the percentage of slip. If delivery pipe is 100 mm in diameter and is 15 m long, find the acceleration head at the beginning of the stroke. (AUC Nov/Dec 2010)

2. Discuss in detail the working of Centrifugal pump. Also write a note on working of jet pump. (AUC Nov/Dec 2010)

3. (i) With the help of neat sketches, explain the features of a volute type and a diffusion type centrifugal pump

(ii)A centrifugal pump delivers salt water against a head of 15 m at a speed of 100 rpm. The vanes are curved backward at 30º 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%.

(AUC Apr/May 2010)

4. (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.

(ii) For a hydraulic machine installed between A and B, the following data is available: At A At B

Diameter 20cm 30cm Elevation 105m 100m 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? (AUC Apr/May 2010)

5. The impeller of a centrifugal pump having external and internal diameters 500 mm and

250 mm respectively, width at outlet 50 mm and running at 1200rpm. Works against a head of 48 m. The velocity of flow through the impeller is constant and equal to 3 m/s. The vanes are set back at an angle of 40º at outlet. Determine

(i) Inlet Vane angle

(ii) Work –done by the impeller and Manometric efficiency. (AUC Apr/May 2011)

6. A three throw pump has cylinders of 250 mm diameter and stroke of 500 mm each. The pump is required to deliver 0.1 m3/sec at a head of 100 m. Friction losses are estimated to be m in the suction pipe and 19 m in delivery pipe. Velocity of water in delivery pipe is m/s, overall efficiency is 85% and the slip is 3% Determine

(i) Speed of the pump and

(ii) Power required for running the pump. (AUC Apr/May 2011)

7. (i) Define

(1) Manometric efficiency (2) Volumetric efficiency (3) Mechanical efficiency

(4) Overall Efficiency of Centrifugal pump.

(ii) The impeller of a centrifugal pump has an external diameter of 450 mm and internal diameter of 200 mm. The speed of the pump is 1440 rpm. Assuming a constant radial flow through the impeller at 2.5 m/s and that the vanes at exit are set back at an angle of

25º, Determine:

(1) The inlet vane angle

(2) The angle, the absolute velocity of water at exit makes with the tangent and

(3) The work done per unit weight. (AUC Apr/May 2012)

8. (i) Explain the working principle of double acting reciprocating pump with a neat sketch. (ii) Length of 350 mm. The speed of the pump is 60 rpm and the discharge is

0.02cumecs of water. Determine (1) The theoretical discharge (2) Coefficient of discharge

(3) Percentage slip. (AUC Apr/May 2012)

9. (i) Compare and contrast Centrifugal pump and reciprocating pump.

(ii)The cross sectional area of a plunger of reciprocating pump equals 1.5 times that of a delivery pipe. The delivery pipe is 60m long and it rises upward at a slope of 1 in 6. If the plunger has an acceleration of 2.4m/s2 at the end of the stroke and separation pressure is 2.5m of water find whether separation will take place.

10. (i)Explain the different types of Reciprocating pumps? (ii)Differentiate pumps and turbines.


UNIT – V: TURBINES

PART - A (2 Marks)

1. Distinguish between impulse and reaction turbines. (AUC Nov/Dec 2010)

2. What is cavitation? How do you prevent cavitation? (AUC Nov/Dec 2010)

3. Classify Pelton turbine according to

(a) The direction of flow through the turbine runner

(b) The action of water on turbine blades. (AUC Apr/May 2010)

4. Define specific speed of a turbine. (AUC Apr/May 2010)

5. What is the use of draft tube? (AUC Apr/May 2011)

6. Define the specific speed of a turbine. (AUC Apr/May 2011)

7. How would you classify turbines based on the direction of flow in the runner?

(AUC Apr/May 2012)

8. Draw typical velocity triangles for inlet and outlet of Pelton wheel.

(AUC Apr/May 2012)

PART –B (16 Marks)

1. A Pelton wheel operates with a jet of jet of 150 mm diameter under the head of 500 m, its mean runner diameter is 0.25 m and it rates with a speed of 375 rpm. The angle of bucket tip at outlet as 15º, coefficient of velocity is 0.98, mechanical losses equal to 3% of power supplied and the reduction in relative velocity of water while passing through bucket is 15%. Find (i) the force of jet on the bucket (ii) the power developed (iii) bucket efficiency and (iv) overall efficiency. (AUC Nov/Dec 2010)

2. Derive the equation for power and work done for the impact of jets on moving curved vanes. Explain the classification of turbines. (AUC Nov/Dec 2010)

3. (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.

(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. (AUC Apr/May 2010)

4. (i) Draw the characteristics curves of turbines and explain.

(ii) An inward flow reaction turbine operates under a head of 25 m running at 200 rpm. The peripheral velocity at 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. (AUC Apr/May 2010)

5. A Pelton wheel generates 8000 kW under a net head of 130 m at a speed of 200 rpm.

Assuming the coefficient of velocity for the nozzle 0.98, hydraulic efficiency 87%, speed ratio 0.46 and jet diameter to wheel diameter ratio 1/9, Determine,

(i) Discharge required

(ii) Diameter of the wheel

(iii) Diameter and number of jets required and

(iv) Specific speed of the turbine. Take Mechanical efficiency is 75%.

(AUC Apr/May 2011)

6. In an inward flow reaction turbine, head on turbine is 32 m. The external an internal diameters are 0.44 m and 0.72 m respectively. The velocity of flow through the runner is constant and equal to 3 m/s. The guide blade angle is 10º and runner vanes are rigid at inlet. If the discharge at outlet is radial, determine

(i) The speed of the turbine

(ii) The vane angle at outlet of the runner and

(iii) Hydraulic efficiency. (AUC Apr/May 2011)

7. (i) Distinguish between impulse and reaction turbines.

(iii) A Pelton wheel is required to develop 8825 kW when working under the head of 300 m. The speed of the pelton wheel is 540 rpm. The coefficient of velocity is 0.98 and the speed ratio is 0.46. Assuming jet ratio as 10 and overall efficiency as 84%. Determine :

(1) The number of jets

(2) The diameter of the wheel

(3) The quantity of water required (AUC Apr/May 2012)

8. (i) What are the various types of draft tube?

(ii) A Francis turbine is to be designed to develop 360 kW under a head of 70 m and a speed of 750 rpm. The ratio of width of runner to diameter of runner ‘n’ is 0.1. The inner diameter of the runner is half the outer diameter. The flow ratio is 0.15. The hydraulic efficiency is 95% and the mechanical efficiency is 84%. Four percent of the circumferential area of runner is to be occupied by the thickness of the vanes. The velocity of flow is constant and the discharge is radial at exit.

Determine:

(1) The diameter of the wheel

(2) The quantity of water supplied

(3) The guide vane angle at inlet and

(4) Runner vane angles at inlet and exit. (AUC Apr/May 2012)