Cs382/Flow Rate Experiment

This is a detailed description of one experiment listed on the CS382 course page

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Goal

The goal of this experiment is to observe the flow rate of a dye plume in the groundwater simulator and note the plume's properties as it the dye travels through sand or gravel. The data gathered here will be used to verify a computer simulation of groundwater contamination.

Equipment

• enVision sand and gravel groundwater simulator
• water soluble dye
• pipette
• water
• ruler
• kitchen timer or some other time measurement device

Procedure

1. Fill the groundwater simulator with fresh water This yields the greatest contrast between the dye plume and surrounding clean water.
2. Open the ocean valve and close the river valve.
3. Make the pump's output approximately halfway between its maximum and minimum.
4. Allow time for the water table to stabilize.
5. Fill the pipette at least halfway full with dye.
6. Insert the pipette completely into well number 1 (confined artesian aquifer)
7. Inject enough dye into the well to create a quarter sized plume.
8. Keep the pipette's bulb depressed until after it is removed from the well to avoid creating a vacuum and sucking dye from the plume back into the well. A little of this may occur as the water level in the well rises to fill the space formerly occupied by the pipette's barrel.
9. Measure the distance from the bottom of the well and the plume's leftmost edge and start the timer in the horizontal plane.
10. Continue to measure the plume's leading edge at regular intervals until the plume has reached well number 8.
11. Repeat this experiment using well number 2.
12. Graph your results.

Results

• Determine the velocity of the plume's leading edge.
  • <math>d(t)</math> = distance between source well and leading edge of plume at time interval <math>t</math>
  • velocity = <math>(d(t2)-d(t1))/(t2-t1)</math>
  • Does the plume's velocity change over time?

• Is there a direct correlation between the flow rate and the plume velocity?
  • How did your two runs differ? What might account for this?
  • Why might the flow rate differ in different parts of the simulator?

Considerations for a Computer Based Simulation

• If the flow rate is not constant within runs, how might we account for this in the simulation?