LAB 4 Water Hammer

Apparatus
Initial Setup
Manual Flow Measurement
Manual Pressure Measurement
Computerized Flow and Pressure Measurement

 Introduction

 Safety Considerations

  • Closed toed shoes are required in the Hydrotechnical Lab
  • Safety glasses are required in the Hydrotechnical Lab
  • Do not stand on the grate under the wave simulator flume as it can shift.

Link to Lab 4 Manual  CIVL315_Lab 4_ Manual_Sep2018_Final

Apparatus

A schematic of the experimental apparatus is shown below. The large vertical tank on the left is the constant head tank and water is brought to this tank from the pump in the basement. The flow of water into the tank is controlled by valve A, labelled “EXP4 Valve A” by the wall. Valve B is a bypass valve, which allows for adjustment of tank level and thus the absolute pressures that can be generated in the system. The TA will set these two valves before the lab session. From the constant head tank, the water flows through a 300 foot long copper pipe, which is coiled to conserve space. Valve C is a computer controlled solenoid valve, which is used to cause the water hammer. Valve D leads to the surge tank and when valve D is fully closed, the surge tank is not considered part of the system. Valve E controls the flow of water through the experiment. When water leaves the pipe system it enters the measuring tank. Valve F controls the flow of water out of this tank. This tank is used to measure flow rate by timing how long it takes to fill a known volume.

Pressures are measured at three points in the system. Each of these points has a valve that can be set to either show the pressure on the gauges or to use the pressure transducers which are connected to the data acquisition computer. Do not alter the valves located at the gauges. The TA will do this for you when necessary.

The data acquisition computer is connected to the three transducers, as well as the two level sensors in the measuring tank and valve C. Details on using the computer are presented in the Procedure section.

Procedure

Initial Setup

The following video demonstrates the initial setup of the water hammer lab. Although the setup will be performed by the TAs, it is important for students to watch this video to better understand the system and the location of the valves.

    1. Valves A , C, and E should be fully open. Valve B and D (surge tank) should be closed.
    2. It is very important that all of the air in the system is removed before beginning measurements. Trapped air has a damping effect and reduces water hammer pressures. T.A. will start up the apparatus 10-15 minutes before you arrive, which should give plenty of time for any trapped air to escape.
    3. Set valve E (the last valve on the copper tube) to the highest flow setting that does not begin to fill the measuring tube on the side of the tank. There should be no water in the clear tube attached to the measuring tank. If there is check that the drain valve is open and close valve E slightly.
      valve E
    4. Open the computer controlled valve (solenoid valve C).
    5. Close valve F (the drainage valve) by pushing it so it points up.

↑top↑

Manual Flow Measurement

  1. Set valve E to the highest flow setting that does not begin to fill the measuring tube on the side of the tank.
  2. Time how long it takes to fill the measuring tank. Use height of the water and simple geometry to determine flow rate.
  3. Open the measurement tank valve and drain the tank. You may repeat the 
flow rate measurement to increase accuracy.

Manual Pressure Measurement

The following video shows the steps needed to open and close the computer controlled valve C. Video 2 (Step 2 & 5)


  1. Verify with the TA that the 3 pressure measurement points are setup for manual measurements.
  2.  Measure the steady state pressure at all of the gauges.
  3. Close the computer controlled valve and read the maximum pressure on each of the gauges.
  4. Open the computer controlled valve and read the minimum pressure at 
each gauge.
  5. Open the surge tank valve.
  6. Close the computer controlled valve and measure the maximum pressure 
on the gauges as well as the period of the water oscillations in the surge
tank.

Computerized Flow And Pressure Measurement

The following video shows you how to switch the 3 tee valves to send pressure from the mechanical pressure gauges to the transducers and to collect one of the waterhammer datasets. Video 3 (Step 1 – 16)

[Video 3]

  1. Switch all the gauges over from mechanical pressure sensing to transducers by adjusting the 3 way tee valve to the transducers (confirm this step with the TA).
  2. You will collect six data sets in total for three different flow rates (high, medium and low) with or without the surge tank. We use a program called DASYlab for data acquisition.
  3. On the waterhammer program, clicking on “CONTINUE” will bring up the data acquisition screen showing real time pressures measured by the 3 pressure transducers on the top graph. The bottom graph will show the actual data collected that you can save to a file.
  4. Make sure the valve D is closed and that the surge tank is not part of the system.
  5. With the measuring tube drainage valve and computer controlled valve open, set the flow rate by adjusting valve E to the highest flow rate that has a steady state water level of zero. So the water level is below the lower acquisition probe.
  6. On computer click the DETERMINE FLOW button to switch to the flow calibration window. If the lower sensor is green even with the measuring tube drainage valve open then close valve E slightly to reduce flow.
  7. Close the Measuring tube drainage valve.
  8. Press START CALIBRATION. Be sure to press start calibration before the lower sensor is activated.
  9. Wait for the calibration to complete.
  10. Open the drainage valve on the measuring tank. You will need to repeat the calibration each time you change the flow rate.
  11. Press RETURN. You will not be able to return until both water level sensors are red.
  12. Close the computer controlled valve, the program will automatically begin collecting data from all the transducers.
  13. After about 15 seconds open the computer controlled valve to record the pressure drop on the same dataset.
  14. Wait for the “Ready” text to display and save your data by pressing SAVE
  15. Select the experimental conditions used to specify the name of the file.
  16. Press RETURN to return to the data acquisition screen.
  17. Open the surge tank valve.
  18. Close the computer controlled valve, the program will automatically begin collecting data from all the transducers.
  19. After 20 seconds open the computer controlled valve to capture the pressure drop on the same 30 second dataset.
  20. Wait for the “Ready” text to display and save your data by pressing SAVE
  21. Select the experimental conditions to specify the name of the file.
  22. Press RETURN to return to the data acquisition screen.
  23. Set valve E to a medium flow rate and repeat steps 7-22.
  24. Set valve E to a low flow rate and repeat steps 7-22. At the end you should have 6 datasets. (3 flow rates) * (Surge on/off)