velocity measurement
On 26th of October we met again next to Pieni-Valkeinen lake solve new tasks.
The aim of our first task was to measure the flow rate of the incoming and outgoing water from Pieni-Valkeinen lake using current meter.
We carried out the measurements for the flow rate at two different locations.
We counted the drills of the current meter a minute for calculating the flow of the water.
After the drill counting we used the cross-section of the stream for calculating the flow of the stream.
For flow velocity calculating we had used this formula:
width: 20 cm
depth: 8 cm
For the outgoing stream the parameters were:
width: 62 cm
depth: 12 cm
For the conversion in the flow velocity of m/s in m³/s, we have used the following formula:
The calculation gives us the information that the incoming water is 2,8 L/s and the outgoing water is 6,6 L/s. The flow rate has a lot of influence factors like: weather, amount of leafs in the stream, temperature and amount of rain.
The following link shows a small video about velocity measurement:
https://drive.google.com/file/d/0B5fOieV0Absob21tT3RoM0ZmcHc/view
field measurements
Our 2nd excersice at this day was to measure the oxygen level, pH, electrical conductivity and the temperature of incoming and outgoing lake water. At the Iso-Valkeinen lake we measured only the incoming flow water.
Also we looked for the smell and the appearance of the water.
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| pic 1: measuring device for measurements |
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| pic 2: Xinyue is measuring the oxygen level at incoming water of Pieni-Valkeinen lake |
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| pic 3: Zhang is measuring the pH of the outgoing water of Pieni-Valkeinen lake |
It was a little bit suprising for us that the conductivity at the incoming flow water was so much higher than the outgoing flow rate. But after a discussion with Teemu we have found out that the way the water travels until it reaches the lake has a big influence on the conductivity. The influence of rain storm, the living area near of the lake and melting water contribute a large part of it.
Also we can see that the pH value is in a neutral range at each of the diffenerent sites.
Please refer the map to our measuring points:
For our next time in the field we have to taking water samples and review of the catchment area.
Thank you for the report. There is something strange in your calculations. In formula V = k*n+D, D is characteristic of the current meter (m/s) and k is hydraulic pitch of the propeller (m). These parameters are determined by tests in hydraulic towing channel. These are given to you readily. You have used "cross-section of the stream" as a D parameter. Please, check this and re-calculate your results.
ReplyDeleteYou have also presented that area is same for both measurement points, incoming and outgoing. Is this really possible with natural streams? It would be nice if you provide also cross-section figure with dimensions for both measurement points.
Great video! Underwater parts and storyteller are amazing! Thank you for providing this kind of material.
You have also found the phenomena of incoming water quality. Electrical conductivity is higher, compared to other measuring points. It was nice discussion about the reason for this.
Check your calculations and update this blog writing after that,
Teemu