Hello:
I have a Watercad (Connect Edition) model where one of my tanks will fill up to about 95% full, and then continue to slowly fill up over time even though i have a FCV before the tank that should prevent any flow from entering the tank when it reaches the 95% full mark.
I will submit the model files for your reference after this post is created.
The tank in question is TANK-B. Run the EPS Run scenario, and view a graph of water level of the tank to see results I mentioned.
Thanks,
Jose
Thanks, Larry. Adjusting these settings does help that issue.
However, now I am noticing another odd result. Graphing TANK-C, the level jumps to full as the simulation starts, then gradually decreases over time, but stays above 85% full, even after long time of 2500 hours. It seems to me that this tank should "float" with TANK-A, since they have the same overflow elevation, and thus should have similar fluctuations in water level. TANK-A predictably has a fluctuating water level based on the controls set up. Shouldn't TANK-C also fluctuate similarly?
Jose,
We looked at your model again and found that not only does it run for around 2500 hours, the hydraulic grade for Tank B continues to climb (slightly) but the Flow into Tank B remains 0.
We attributed this to “numerical noise” (or “ghost flow”). This Wiki article explains this further. And to make it even more noticeable, the Accuracy in Calc Options had been changed from .001 to .01 because with the Default settings, the model was Unbalanced.
We also found that using the latest version of the solver (Engine Compatibility Mode) – 2.2.0 rather than 2.00.12– and the Accuracy setting put back to the Default .001, the model converged.
Please see if this is what you see and if you get good results using the latest version of the solver.
Thank-you,Larry
Jose Ortiz,
I'm still looking at your model but I am not seeing any Flow out of Tank B but I do see the Hydraulic Grade rising.
I'm going to consult with Development about why I see that and get back to you.
Here is a good reference article for Graphing flow coming out of a tank.
I'll post again here after talking to Development.