CE322 Hydraulic Laboratory Component General Information, Requirements, and Instructions (Prepared by Dr. Jim Liou, Department of Civil Engineering, Univ. of Idaho) CONTENT General Requirement. 2 Lab Format Lab Reports Self-evaluation Grading of Lab Reports Reference Guidelines for Preparing and Grading Rubric of Lab Reports 4 List of Individual Lab Exercise and Objectives... 6 Flow Measurement and Energy Loss in Pipes 7 Water Hammer, Wave Speed, Line Pack, and Attenuation...11 Pelton Turbine... 15 Centrifugal Pump... 18 Flow Measurement, Channel Transition, and Hydraulic Jump..... 23 Channel Resistance and Water Surface Profile. 25 Appendix Sample Peer Evaluation Form 27 Prepared for CE322 by C. P. Liou, Page 1 of 26
General Requirements Lab Format All lab sessions will be conducted at the Hydraulics Laboratory in BEL G6. At the beginning of each lab session, the instructor or lab technician will demonstrate the usage and function of the equipment and instrument involved. Afterwards, you as a group is expected to complete the lab unassisted and unsupervised. Each lab should last no more than three hours. With tasks well planned beforehand, the duration can be shortened, sometimes considerably. Before each lab session, you should read the lab description (attached), plan tasks, and divide responsibility for data taking, sample calculations, data reduction and analysis, and report writing. Although unsupervised, assistance is available. If you encounter a problem and cannot overcome it, please see Dr. Erik R. Coats in BEL 129 or Mr. Don Parks, Lab Technician, in BEL G3. Lab Reports Lab reports are due one week after each lab session. A general guideline for preparing the lab report is given in the next section. Self-evaluation After the submission of each lab report, a confidential peer-evaluation should be completed by each individual and emailed to the instructor. The peer evaluation form attached to the end of this handout should be used for this purpose. In general, if no problem is revealed by the self evaluations, a common mark (i.e., same mark for all group members) will be assigned. Grading of Lab Reports Reports will be graded for technical content and for writing, For technical content, the rubric is given in the next section. For writing, miss-spelling, and muddled thoughts will cause you points. Reference Other than the material in this packet, there is no required text. However, the following reference is very helpful: An Introduction to Error Analysis The Study of Uncertainties in Physical Measurements, 2 nd Edition, John R. Taylor, University Science Books, 1997, ISBN 0-935702-75-X. The instructor has one copy available on loan to lab groups. Prepared for CE322 by C. P. Liou, Page 2 of 26
Guidelines for Preparing and Grading Rubric of Lab Reports The following main sections are required. 1. Introduction (all paragraphs in Introduction should be brief and concise) What is this lab for? What do you want to accomplish? What are the main findings? How is this report organized? 2. Theory Describe the theory involved in your own words. Cut-and-paste passages from another source is not acceptable. Relate the theory to the lab. What and to what extent do you expect the data to verify with the theory? 3. Approach Describe the work performed in a logical sequence. Describe any difficulties encountered and note the anticipated effects. 4. Results Establish uncertainty bounds for all direct measurements and derived quantities. Describe the results, including uncertainty bounds, in words and in plots, tables, etc. 5. Discussions How the data (observations) relates to theory? Explain differences between theory and data in terms of assumptions and uncertainties. 6. Design of Experiment Envision a different design of the experiment to achieve the same learning objective (described for each lab experiment below). Include the following in the description of the design: a schematic, a functional description, and a list of quantities to be measured. 7. Appendix 1 Raw data as recorded during the lab session. 8. Appendix 2 Sample calculation. During a lab session, carry out calculations for one data point from beginning to end. This must be done by hand calculations with a calculator. The sample calculations serves several purposes: (1) ensures that no data items are missing; (2) helps you develop a feel for the magnitude of quantities involved; (3) show your thought process in data reduction. No specific format of sample calculation is required. Sample calculations generated after the lab session defeat the purpose and are not accepted. Prepared for CE322 by C. P. Liou, Page 3 of 26
Appendix 3. Details of data reduction using Mathcad or Excel. The lab report must show the progression of thoughts and how parts fit together. A collection of parts completed by individuals without careful editing and integration is not acceptable. Keep the following in mind when editing: 1. be complete: what, how, why, when, where 2. be clear: format, order, word choice, sentence structure 3. be coordinated: logical transitions of thoughts Exam questions may come from the lab experiments. Each member of the group should understand and agree with the whole content of the report. Before submitting, each member should affix his or her signature on the cover sheet of the report indicating that he or she has proof-read the report. Prepared for CE322 by C. P. Liou, Page 4 of 26
List of Individual Lab Exercise and Objectives Lab. 1: Flow Measurement and Energy Loss in Pipes Objectives: to become familiar with some basic pressure and flow measurements, and to gain an understanding of head losses of incompressible flow in pipes. Lab. 2: Water Hammer, Wave Speed, Line Pack, and Attenuation Objectives: to observe the phenomenon of water hammer in a long copper piping system, and to quantify wave speed, potential surge, line pack, and attenuation. Lab. 3 Pelton Turbine Objectives: to obtain a feel on what the water horsepower, the brake horsepower, and the efficiency of a hydraulic machinery are, and to see that a turbine can be operated over a range of speeds, and that there is an optimum operating point. Lab. 4 Centrifugal Pump Objectives: to understand the pump characteristics, and to see how the performance data of a pump is established and presented. Lab. 5 Flow Measurement, Channel Transition, and Hydraulic Jump (if time allows) Lab. 6 Channel Resistance and Water Surface Profile (if time allows) Objectives: (1) to understand the occurrence of critical flow and the usage of critical flow section as a flow meter, (2) to understand the concept of specific energy as applied to a transition, and (3) to verify the momentum and the energy principles as applied to a hydraulic jump. (If time does not permit at the end of the semester, labs 5 and 6 will be replaced by a class demonstration and homework exercise.) Prepared for CE322 by C. P. Liou, Page 5 of 26
CE322-Hydraulics Flow Measurement and Energy Loss in Pipes Objectives The objectives of this experiment are: to become familiar with some basic pressure and flow measurements, and to gain an understanding of head losses of incompressible flow in pipes. Tasks to be accomplished 1. Calibrate a Venturi flow meter. 2. Determine the Darcy-Weisbach friction factor for a pipe at two Reynolds numbers. 3. Determine the head loss characteristics of a gate valve at three different openings. Equipment Description The Scott Fluid Circuit System will be used for this experiment. A schematic of the circuit is shown on page 7. Valves 45 and 52 are throttled, separately, for regulating flow. The remaining valves are used to set the flow path. They should be either fully open or fully closed unless otherwise stated. The supply reservoir is vented at the top. The sight glass attached to the reservoir can be used to determine water level inside. Make sure the reservoir is about half full throughout the experiment. There are two independent differential manometers shown in the schematic. The finger screw at the top of each unit is used to vent air bubbles and, separately, to trap air as manometer fluid. During differential head measurements, the screws must be tightly closed. Venting air pockets trapped in the circuit and in the manometer sensing lines will be demonstrated in the class. General Procedures 1. Venturi Flow Meter Calibration. You can use any combination of valves to provide flow through the Venturi meter. Valve 52 should be fully closed and valve 45 should be used as a throttling valve to control the flow-rate. At this configuration, the water is wasted and does not return to the reservoir. Tap water must be fed to the reservoir at the same rate as that through valve 45. Use the reservoir level as a guide to adjust the faucet. The flow-rate through the Venturi is measured by weighing the water discharged through valve 45 over a time. A bucket, a scale, and a stop watch will be used for this purpose. Fill the bucket near capacity to obtain accurate flow-rates. Prepared for CE322 by C. P. Liou, Page 6 of 26
Once the reservoir level becomes constant, you can take time to obtain the differential manometer reading. You need to estimate average readings as the water columns in the manometer fluctuate due to turbulence. Note the range of fluctuations as they are needed to establish error bounds. You should obtain at least ten (10) pairs of manometer reading and volumetric flow-rate data to generate the calibration curve for the Venturi flow meter. During the flow-rate measurement, also measure the water temperature for use in Task 2. 2. Darcy-Weisbach Friction Factor Determination. Use the Venturi flow meter to obtain the volumetric flow-rate through pipe 3. The flow direction can be either way, depending on your valve configuration. The differential head between taps 24 and 32 is measured by the second differential manometer. (The first differential manometer is used by the Venture.) Both valve 45 and the fill valve should be closed fully. The water is now recirculating through the system. Use valve 52 to control the flow-rates. Set the flow-rate at the top of range tested in Task 1. When the flow is steady, read the head difference between taps 24 and 32. Obtain the second pair of data at a flow-rate half as large as the first one. (Can you estimate the desired differential manometer reading for the Venturi directly without consulting the calibration curve?) Calculate the Darcy-Weisbach friction factors and the Reynolds numbers for the measured data. Plot your results on a standard Moody diagram. Do they match the standard data? Explain why they do or don't match. Use a pipe inside diameter of 0.785 inches in your calculations. You must measure the length of the pipe between taps 24 and 32. Also measure the temperature of the water (as noted in 1) so that a proper viscosity is used. 3. Gate Valve Head Loss Characteristics. Valve 45 and the fill valve should be closed fully. The water is recirculating through the system. Use valve 52 to control the flow-rates. Set the remaining valves such that the flow through the gate valve on pipe 3 is common to the flow through the Venturi flow meter. The head difference between the two sides of the gate valve is measured by the second manometer. (Again, the first manometer is used by the Venturi meter to obtain flow-rate.) It takes about 5.5 turns to move the valve from full open to full closed position. You are required to obtain a flow versus head loss curve at three valve settings. These settings Prepared for CE322 by C. P. Liou, Page 7 of 26
are: 1 turn open, 2 turns open, and full open. Use at least 5 data points to establish the curve for the two larger valve openings. Make sure that the data points cover as a wide range of flow as possible. For the case with the smallest opening, the manometer may be too short when the flow is high. When this occurs, three data points (at lower flow-rates) will be sufficient. Plot all three curves on one graph paper. Discuss the results. At a fixed valve position, what is the length of pipe that will produce the same head loss as the valve itself? Make sure that you turn the pump off after the experiment. Because the pump runs very quietly, it may be left on unknowingly. Minimum Report Requirements The following items must be provided or addressed in your report. 1. Tables of raw and processed data. 2. One complete set of sample calculations. If you use a spreadsheet program to manage data, you need to provide the algorithms used so that your thought process can be understood. 3. A brief discussion for each completed task. (Do the results make sense? What do they confirm or disprove? What is the point of this task?) 4. Estimation of error bounds for the results. State the basis of your estimations 5. Description of an alternate design of this experiment There is no required format for the report. You are encouraged to develop your own style of report writing. Other Equipment 1. stopwatch, 2. thermometer, and 3. tape measure. (all in a tool box). Other Information You should allow at least three hours to complete this lab session. Plan the test and divide the work evenly. You also need to meet and prepare the report. Make sure everyone is aware of all aspects of the lab. As you become familiar with the process, future labs will become easier and faster. It is essential that calculations on one data point be carried out during the lab session. It will help you to prevent errors and to alert you of missing data before it is too late. Prepared for CE322 by C. P. Liou, Page 8 of 26
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CE322-Hydraulics Water Hammer, Wave Speed, Line Pack, and Attenuation Objectives The objectives of this experiment are: to observe the phenomenon of water hammer in a long copper piping system, and to quantify wave speed, potential surge, line pack, and attenuation. Equipment Description The test loop is made of cooper (red brass) type k tubing. It has an internal diameter of 0.995 inch and a wall thickness of 0.065 inch. As a material, red cooper has a Young s modulus of elasticity between 15*10 6 to 17*10 6 psi. The length of the tubing is approximately 1100ft. The pipe is mounted in such a way that it forms a loop like a racing track. The pipe inlet is located in the water sump below floor level. About 31.5 ft from the pipe entrance on floor level is a pump with a variable frequency drive. The pump speed may be adjusted by pushing up or down buttons on variable frequency drive panel mounted on the wall near the pump. For personal and equipment safety, the frequency should never exceed 30 Hz during this lab. Water circulates in the loop and empties into the sump. At the outlet of the loop are two quarter-turn valves. One of them is connected to a hose. The other is closed and is not involved in this lab. For this lab, two piezoelectric pressure transducers (Keller PAA-25) are used to capture the rapidly varying pressures of water hammer. The transducers convert the source pressures into DC voltages which are written into a data file by the PC-based data acquisition system. The voltage is proportional to the pressure level. The calibration of the transducers are 0 Volts at 0 psi (absolute), and 10 Volts at 200 psi (absolute). The linear distance along the pipe between the transducers is 1097 ft. The elevation of these transducers are the same. The data file is a text file formatted in three columns. Column 1 is time in seconds, Column 2 the pressure (in volts) close to the pump. Column 3 is the pressure (in volts) near the loop outlet. Bring a USB thumb drive so you can copy the data file to your thumb for offline processing. A bucket, a weighing scale, a stopwatch, and a thermometer are provided to measure the volumetric flow rate prior to water hammer. Procedures 1.) On the pump control panel, push the start button to turn the pump on. Increase the power line-frequency to 60 Hz by pressing the up button. Open wide the valve at the loop outlet. (i.e., the valve connected to the hose). Let the flow go through the loop for several minutes to force out any trapped air in the loop. Prepared for CE322 by C. P. Liou, Page 10 of 26
2.) Reduce the power-line frequency down 30 Hz by pressing the down arrow on the wall mounted control panel. Let flow stabilize and then measure the volumetric flow rate. Be sure to keep the pipe hose at a constant elevation and clear form the bucket when doing this. Take 3 flow measurements and establish an average flow rate. Note the uncertainties involved in measurements. Also measure the temperature of the water. 3.) Start a data acquisition session. The session only last 5 seconds. Have one person at the computer control while another person is poised to slat-shut the outlet valve. On the command of the control and 1 second into the session, shut the valve. Five seconds later, open the discharge valve so the pump is not pumping against a dead end for too long. The instructor will demonstrate this fast sequence. 4.) At this point we have the data to show what happens when the outlet valve is suddenly closed. A computerized strip chart provides the visual for the data. Make note of the steady state frictional head loss, the potential surge, the line packing, and the attenuation of the water hammer. 5.) After seeing what is going on, you are ready to take data on your own. Take three sets of data to ensure the phenomenon is repeatable. After the lab session, import the data into a spreadsheet program or Mathcad and plot the digitized pressure traces. Can you pick out the potential surge and the line pack? Compute the Darcy-Weisbach friction factor from the measured flow, the average inlet and outlet pressures collected by the computer prior to water hammer generation. Also compute the potential surge and the wave speed. Computed the water hammer wave speed three ways: (1) by the theoretical approach, (2) by the potential surge relationship, and (3) by wave travel time. Discuss the results and estimate the error bounds. Minimum Report Requirement 1. Show all raw data and one set of complete calculations. 2. Establish error estimations. 3. Discuss the results. 4. Describe an alternate design of this experiment Reports are due one week after data is taken. Prepared for CE322 by C. P. Liou, Page 11 of 26
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CE322-Hydraulics Pelton Turbine Objectives The objectives of this experiment are: to obtain a feel on what the water horsepower, the brake horsepower, and the efficiency of a hydraulic machinery are, and to see that a turbine can be operated over a range of speeds, and that there is an optimum operating point. Equipment Description This lab is to be performed on a hydraulic bench and a model Pelton impulse turbine. The bottom portion of the bench is a sump tank. A centrifugal pump draws water from the sump and feeds it to the turbine. The spent water is dumped into a volumetric measuring tank. The water is eventually returned to a sump tank for recirculation. Located at the lower left side of the bench is a pump discharge valve. This valve should be fully open during tests. The turbine sits over the side channel on the top of the bench. The flow into the turbine is controlled by a spear valve assembly. The other function of this assembly is to form a solid water jet directed at the turbine buckets from left. A pressure gauge mounted on the assembly indicates the pressure head (in meters) of flow approaching the spear valve. For this experiment, we will determine the efficiency of the system (the spear valve assembly and the turbine) instead of the turbine runner alone. The jet velocity, although not directly measurable, can be estimated from the pressure head with some approximating assumptions. A load to the turbine is applied through a tensioning device mounted on a support frame over the turbine. This device is made of a belt with its ends attached to two spring balances dangling down from the support frame. The belt is looped around a drum mounted on the turbine shaft. By raising (lowering) the device, the torque applied to the running turbine can be increased (decreased). Facing the turbine, its rotation is counterclockwise. The spring balance on the left will indicate a greater force than that of the right. The difference of these two forces multiplied by the radius of the drum (3 cm precisely) yields the torque applied to the turbine. Any offset of the force readings should be corrected. The speed (in rpm) of the turbine can be measured by a digital tachometer. Aim the tachometer at the reflective patch on the turbine shaft and press the white switch on its right side to obtain readings. Speeds from 10 to 30,000 rpm can be measured. The rpm uncertainty is: 0.1 rpm from 10 to 1000 rpm, 1 rpm from 1000 to 6000 rpm, and 2 rpm from 6000 to 30,000 rpm. Please keep this tachometer dry as it is not water-proof. General Procedures Prepared for CE322 by C. P. Liou, Page 14 of 26
1. Make sure the spear valve and the pump discharge valve are fully closed. Plug in the power cord. Measure the distance between turbine shaft center and the center of the buckets. 2. Turn the pump on (the switch is located at the lower left panel). Turn the pump discharge valve to its wide-open position. This valve should remain wide open during the lab. 3. Lower the tensioning device so that the belt is not touching the drum. 4. Open the spear valve slowly until the pressure gauge indicates a pressure head of 20 meters. 5. Measure the turbine speed. This is the runaway speed at the set spear valve position. 6. Measure the flow rate. This is done by dropping (i.e., closing) the dump valve and measuring the time required to collect a given volume of water. A sight class and scale on the lower left panel of the hydraulic bench are to be used for this measurement. Open the dump valve when finished. 7. Raise the tensioning device to apply a torque to the turbine. The turbine will slow down. Obtain its rpm. Also, obtain the force readings from the two balances. 8. Repeat step 7 no fewer than 15 times. You want to span the turbine speed from runaway to nearly zero rpm. At a very low rpm, the belt slips, the balances jump wildly, and a constant turbine speed cannot be maintained. Use your judgment to get as low a turbine speed as possible but still can get valid data. 9. Repeat the volumetric flow rate measurement. 10. Open the spear valve further until a pressure head of 10 meters is reached. 11. Repeat steps 5 to 9. 12. Close all the valves. Turn the pump off and unplug the power cord. Minimum Report Requirement 1. Tabulate all raw data and provide a complete set of sample calculations on one data point. 2. Establish water horse power versus bucket speed curve at the two spear valve positions. 3. Establish brake-horse power versus bucket speed curve at the two spear valve positions. Prepared for CE322 by C. P. Liou, Page 15 of 26
4. Establish system efficiency versus bucket speed curve at the two spear valve positions. 5. Discuss the results, including experimental errors and uncertainties. 6. Describe an alternate design of this experiment Report Due Date: One week after data is taken. Prepared for CE322 by C. P. Liou, Page 16 of 26
CE322 Hydraulics Centrifugal Pump Objectives The objectives are: (1) to establish pump performance curves and (2) to verify the homologous theory. Develop an understanding on the characteristics and operation of centrifugal pumps through these activities Equipment Description A centrifugal pump and a motor are mounted on a test stand (see Fig. 1). Electric power is fed to the motor via a variable frequency drive. The pump takes suction from a tank (see Fig. 3) via a suction pipe. On the discharge side of the pump are a control valve, a dial pressure gauge, and a Venturi flow meter (see Figure 2). A second control valve is located on the discharge pipe between the Venturi and the pipe outlet to the tank (see Fig. 3). Water in the tank is conveyed to the pump inlet through the suction pipe, upon acquiring the total dynamic head of the pump, the water goes through the Venture meter and re-circulates back to the tank. Figure 1 Centrifugal pump (left), a torque sensor (middle) and a motor with a force gauge (right) Prepared for CE322 by C. P. Liou, Page 17 of 26
Figure 2 Pump discharge control valve, pressure dial gauge, and Venturi flow meter During test, the control valve between the pump discharge and the dial pressure gauge should remain wide open. Use the control valve near the discharge pipe outlet (see Fig. 3) to regulate the flow. Prepared for CE322 by C. P. Liou, Page 18 of 26
Figure 3 Tank, flow control valve, carrier-demodulator for the differential pressure transducer (left on shelf), power supply for the torque sensor (middle on shelf), and variable frequency drive (right on shelf) The power input to the test stand is measured by a Watts meter. The torque exerted by the motor on the pump shaft is measured in two ways: (1) by a torque sensor, and (2) by a force gauge with a known moment arm. A hand-held tachometer is used to measure the rotational speed of the pump. The measured torque and the rotational speed enable the power input to the pump (which is the same as the power output from the motor) calculated. From the water level in the tank (measurable using a staff gauge), the flow rate (measurable using the Venturi), pressure at pump discharge, and the known elevations of the suction pipe and the dial pressure gauge, the total head at pump suction and discharge can be calculated. The difference between the two is the total dynamic head produced by the pump at the given flow. Consider all head losses (entrance, elbow, and friction) along the suction pipe in calculating the total head at pump suction. Additional information are given below: Suction pipe centerline elevation: 0 in (i.e., this the datum for elevations) Suction pipe length: need to be measured. Pump suction pipe inside diameter: 1.025 in Pump discharge pipe inside diameter: 0.805 in Venturi throat diameter: 0.48 in Prepared for CE322 by C. P. Liou, Page 19 of 26
1.1 Venturi Calibration 1.086 1.072 1.058 1.044 K 1.03 1.016 1.002 0.988 0.974 0.96 1 10 3 1 10 4 1 10 5 1 10 6 1 10 7 SQR(2 g dh)*(d/nu) Figure 4. Calibration curve of the flow coefficient K for the Venturi meter (See Roberson and Crowe Figure 13.13 and CE322 first Lab) Elevation of the pressure gauge at pump discharge: 8.625 in Supply tank bottom elevation: 2.25 in. This is the elevation of the zero reading of the staff gauge affixed to the inner wall of the tank. The calibration flow coefficient K for the Venturi meter is provided in Fig. 4. The d horizontal axis of Fig. 4 represents 2g h, where g is gravitational acceleration (32.2 ν ft/s 2 ), h is the differential piezometric head (in ft) between the Ventuii approach section and the throat, d is the diameter at Venturi throat, and ν is the kinematic viscosity of the fluid in ft 2 /s. h is related to the output of the differential pressure transducer. (8 Volts corresponds 10 psi, linear). Knowing K, the flow can be computed from Q = KA 2g h o Prepared for CE322 by C. P. Liou, Page 20 of 26
The output from the torque sensor is Volts. This voltage output, corrected for any offset, is converted to torque in inch-ounce by ( ) ( 44 3825 0 00322 ) Γ in oz =. +. *Volts *Volts The moment arm to be used in calculating the torque using the force gauge is 4.06 inches. Both methods of torque measurements should be used and reported. Procedure 1. Before turning the power on, ensure the pump discharge control valve is fully closed. 2. Turn on the power, adjust the frequency of the input power to nearly zero. 3. Gradually open the pump discharge control valve. Ensure both valves are now fully open. 4. Gradually increase the power frequency to 60 Hz. Once there, record tank level, dial pressure gauge reading, Venturi meter output, torque sensor output, and the reading from the Watts meter. 5. Reduce the flow by adjust the control valve near the discharge pipe outlet (the valve at the pump discharge should stay wide open) and record the data. Repeat this at least ten times in such a way that your flow data is more or less equally spaced between 0 and the maximum. 6. Reduce the power frequency to 30 Hz. Repeat the same to obtain the data set at the lower pump speed. Minimum Report Requirement 1. Outline the theory behind pump performance characteristics and homologous theory 2. Establish the head versus flow and efficiency versus flow curves (pump efficiency, motor efficiency, and overall efficiency) for the two pump speeds 3. Establish the head versus flow curves in terms of homologous variables 4. Uncertainty bounds must presented as an integral part of your results 5. Discuss the results 6. Describe an alternate design of this experiment 7. Include raw data sheets, sample calculations, and all data reduction in an appendix Prepared for CE322 by C. P. Liou, Page 21 of 26
CE322 - Hydraulics Flow Measurement, Channel Transition, and Hydraulic Jump Objectives There are three objectives: (1) to understand the occurrence of critical flow and the usage of critical flow section as a flow meter, (2) to understand the concept of specific energy as applied to a transition, and (3) to verify the momentum and the energy principles as applied to a hydraulic jump. Equipment Description A flume is constructed from Lucite sheets. It has a width of 3.8 cm and a length of 8.6 m. A ramp is inserted near the mid-length of the flume. The upper-end of the flume rests on a rigid support. The lower-end rests on a thick pin inserted in a support frame. The slope of the flume can be adjusted by lifting up the lower end of the flume with a wrench, remove and reinsert the pin to a new position, and lower the flume to the pin at the new position. Water is supplied to the head box by pump located at the free-fall end of the flume. Water flows through the flume and free-falls into the pump supply reservoir. General Procedure Make sure the pump discharge valve is closed. Turn the pump on. Slowly open the discharge valve so that the water level in the head box is about two-thirds full. Using the valve to make small flow adjustment to create: (1) a subcritical flow region upstream from the ramp, (2) a supercritical flow region immediately downstream from the ramp, (3) a hydraulic jump, and (4) a subcritical flow region between the jump but and the free-fall. Once the valve position is set, it should remain unchanged throughout this lab exercise. The slope of the flume is preset so that you can create the required flow conditions with the valve. Please do not change the slope of the channel. The scales (two vertical and one along the channel) affixed to the flume are not involved with this lab exercise. In the following tasks, each member of the team should make a complete set of measurements. All measurements should be used in your team report. Flow measurement A weighing tank and a stop watch are provided. Use the deflector to direct the falling jet into the weighing tank for flow measurement. Measure the depth of critical flow sections (there are two) and compute the flow rate. Do the calculated values match the measured one within the uncertainties of measurements? Transition Prepared for CE322 by C. P. Liou, Page 22 of 26
Measure depths of flow at the approach section to the ramp and at the section at the midpoint of the ramp. Can you explain the observed trend of changes in flow depth? How do the measured depths compare with theory? Hydraulic Jump Measure the depth of flow before and after the jump. Use your judgment to decide where these measurements should be. Verify the conjugate depth ratio versus Froude number relationship (Eqs. 7-25 and 7-26 of the text). Also verify the energy loss-relationship (Eq. 7.28 of the text). Minimum Report Requirement 1. Tabulate all raw data. 2. Provide one set of complete sample calculations. 3. Discuss the results in terms of assumptions, uncertainties, etc. 4. Describe an alternate design of this experiment Prepared for CE322 by C. P. Liou, Page 23 of 26
CE322-Hydraulics Channel Resistance and Water Surface Profile Objectives The objectives are (1) to understand open channel's resistance to flow by determining the Manning's n value, (2) to understand water surface profiles physically and computationally. Equipment Description A flume is constructed from Lucite sheets. It has a width of 3.81 cm and a length of 8.6 m approximately. The upper end of the flume rests on a rigid support. The lower end rests on a thick pin inserted in a support frame. The slope of the flume is adjustable by changing the pin position. Use the wrench to lift the lower end of the flume so that the pin can be repositioned. Water is recirculated through the flume by a pump. The flow rate is adjustable by throttling the discharge valve of the pump. Flow rate is measured by a weighing tank and a scale. If the water is wasted during flow rate measurement, than you need to make up the lost water with the hose connected to the building water supply. You need to keep the water level in the pump constant. Otherwise, the flow rate may vary over time. Two vertical scales are affixed at the two ends of the flume. A third scale is affixed along the flume. With these scales and using a level, the slope of the flume can be determined. General Procedure Turn the pump on and have water circulating in the flume. Set the flume to a mild slope (hydraulically speaking). Make further flow adjustment until a smooth M2 profile is created. Use the level to record needed data for channel slope determination. (The level will be set up and ready to record data.) Use the weighing tank to determining the flow rate. Use the flow rate to calculate the critical depth. Locate the channel cross-section near the free-fall where critical flow occurs. This section is the control for the M2 profile. Starting at the control section, record the flow depth and the corresponding distance along the channel so you have a measured M2 water surface profile. By using the measured flow rate and the control section, and by assuming a range of Manning's n values, a set of M2 profiles can be computed with the direct step method. You should write a simple compute program or to use a spread sheet program for this purpose. The Manning 's n associated with the computed profile that best matches the measured profile is the answer. Minimum Report Requirement 1. Tabulate all raw data 2. Provide one set of complete sample calculations with uncertainties indicated Prepared for CE322 by C. P. Liou, Page 24 of 26
3. Provide the listing of the computer program (or make explicit cell formulas if you use a spread sheet) for the water surface computations 4. Discuss your results 5. Describe an alternate design of this experiment Prepared for CE322 by C. P. Liou, Page 25 of 26
Appendix Sample peer evaluation form (adopted from ABET student Outcomes by Gloria Rogers, http://www.abet.org/defining-student-outcomes/) Please rate each member of the team on the following scale: Unsatisfactory Developing Satisfactory Exemplary 1 2 3 4 Name Attribute 1 2 3 4 Carlos Sara Jeffrey Rima Researched and gathered information Fulfilled team roles when assigned Shared in the work of the team Demonstrated good listening skills Researched and gathered information Fulfilled team roles when assigned Shared in the work of the team Demonstrated good listening skills Researched and gathered information Fulfilled team roles when assigned Shared in the work of the team Demonstrated good listening skills Researched and gathered information Fulfilled team roles when assigned Shared in the work of the team Demonstrated good listening skills Prepared for CE322 by C. P. Liou, Page 26 of 26