...
The Point of failure experiment will evaluate the point at which the diameter of the LFOM is too small to accomodate accommodate the flow throuhg through the riser pipe. At a certain point the water will back up in the pipe and then there won't be free flow from the orifice into the riser pipe. The small diameter riser pipe was tested at the pilot plant. The hypothesized results are a relationship taht that is the same as the tearget realationship target relationship until failure. The results showed a linear relationship with a lower ratio of flow/depth than the predicted for all flow rates. The hypothesis for these results is that instead of a point of failure there is total failure. If the pipe is inappropriately sized then the LFOM fails for all flow rates.
...
In order to more accurately calcualte calculate the optimal LFOM diameter it is necessary to know the point at which the diameter is to too small and will achieve failure. The point of failure experiment will test a prototype design under predicted failure conditions. The point of failure is predicted assumeing conservation of momentum.
...
The documentation of the program used to for these calcualtions calculations is available here
- The new diamter diameter of 1.5in was used in calculating the hole spacing below: the drill bit size is still 3/8 in
- The riser pipe will be constructed from PVC pipe and a reducer will be used to connect the new riser pipe to the old aparatus apparatus flange from the previous experiment, see the old page for information on the previous set-up.
...
- Record the water height for flows between 8 and 22 GPM in approximately 1 GPM increments
- *The flow meter has an accuracy of +/- 0.25% of the flow rate.
- The flow meter is composed of two pieces and is produced by siemensSiemens.
Figure 1: The sensor with display is pictured above and the model is SITRANS F M MAG 3100, statistics for the sensor are available at the Seimens website.
Figure 2: The microprocessor-based transmitter that displays the data is pictured above and the model is SITRANS F M MAG 6000, statistics are available at the siemens Siemens website.
Photograph of Point of Failure
...
- The data collected from three trials is available as an excel document.
- There is a correction factor for the water heights because the first hole isn't at the bottom of the bucket. There is an offset of 4.875 inches. Also the lengthy decimals result from using english English units with eights and sixteenths inches.
Correlation between Flow and Water Height
...
Difference Between the Recorded Data and Predicted Values as a Function of Flow Rate
Percent Deviation Between the Recorded Data and the Predicted Values as a Function of Flow Rate
...
The results of the experiment were contrary to the expected results. Originally it was assumed that there was a certain maximum flow rate for a pipe, if the flow rate exceeded a maximum value the water entering the riser pipe wouldn't be able to leave quickly enough and the water would back up in the pipe. THe The results showed an alternative situation. The pipe was sized to reach the failure point at 62.5 L/min (half the maximum flow rate of the pilot plant - 125 L/min). The results showed a linear relationship between flow rate and height for all of the flow rates, the difference was that the slope for the pipe had a different slope than the predicted values. The lack of agreement between theory and experimental values over the entire range suggest that the LFOM failed over the entire range of flows.
...
The perplexing results may be due to the fact that there we were not witnessing a point of failure, a flow rate at which a LFOM will fail, but a complete failure. If the pipe is sized too small to accomodate accommodate the flow rate which the orifice pattern is designed to support then the LFOM will fail for all flow rates. This hypothesis would agree with the results. It would be beneficial in future research to test the LFOM created above with a diameter of 1.5 inches with an orifice pattern designed to handle the maximum flow rate for the pipe, 62.5 L/min. It would also be interesting to apply a flow rate in excess of the 62.5 L/min and watch the system for evidence of failure.