Hi,
I am trying to balance the flow going into a reservoir. However, there is a snapshot showing a spike which has made me very hard to see the tolerance. I realized the spike happened when the reservoir level reach to the highest level i set at the control or maximum level. Could anyone suggest what is the best way to set a control at the reservoir?
Mark
Hi Mark,
Your solution is not solved my problem yet.
This is about reservoir overflow. For my model, there are few reservoirs are overflow. Take example of tank label R-00014, the maximum level is 6m and the inflow is from borehole pump which is pump for 24hrs nonstop. If i set the control to go off at 5.9m, there would zero flow when level reach the max level which is in reality there are still have a flow into the reservoir. That is why the flow at the inlet have a spike.
For my model calibration to solve this i had introduced a dummy reservoir which is allowed the overflow and increased the max level and level to shut at control. That is why u doesn`t see the problem at the area i mentioned before. However, added the dummy reservoir to solve this problem doesn`t looked practical. I just hope that u could provide other solution for this problem.
Your help really appreciated.
Azizah
Azizah,
I'm not sure if what I did was correct for how you have your model setup, but I tried to just delete all the reservoirs the you had the named "dummy". After I did that I think I saw the spikey opening and closing pattern problem you might have been referring to on pipes P-08299 and P-11333. It looks like it was the same problem as before too and has the same solution, if I'm seeing the problem you were referring to in your post above. I'm not really sure if I am though because the exact problem isn't 100% clear to me.
Based on what I have seen though from the location that you referenced in your screen capture above your problem is with the control labeled LC25268. The control reads: IF R-00014 Level >= 6.49 m THEN P-11050 Pipe Status = Closed ELSE P-11050 Pipe Status = Open
The problem with the control is that once the level of the tank drops below 6.49m then the pipe opens again. Just as with the last problem with the controls this type of setup will can cause sharp spikes flow because you're opening and closing the pipe rapidly until the flow out of the tank is great enough to drop the tank level fast enough and far enough below the point where the controls oscillate back and forth. What you'll need to do in order to fix this issue is make sure there is some kind of gap between the levels that cause the pipes to open and close. For example, "IF R-00014 Level >= 6.49 m THEN P-11050 Pipe Status = Closed" and then have a separate statement that reads, "IF R-00014 Level <= 3.0 m THEN P-11050 Pipe Status = Open". Keep in mind that these are just example levels and that you should use whatever levels these tanks operate at in the real systems for creating your controls.
The other issue that you're running into is I don't think you are seeing all the little changes that are made in between your time steps because you have the "reporting time step" property in your calculation options set to report at a constant time step of 0.25 hours. When you're looking at the graphs this prevents you from seeing everything that occurs in between those 15 minute intervals. If you set the reporting time step to <All> that will allow you to see everything that is happening over the entire course of your simulation when you graph elements.
If there are still saw-tooth pattern flow problems in your model after making these changes have a look at the controls related to the area in question and make sure there is some gap between whatever is controlling the elements. If there are still issues please let me know what you are seeing and where exactly you're seeing it, so I know exactly where to look in your model to observe the issue.
Regards,
Answer Verified By: Sushma Choure