Extended time period simulation EPANET 1

[Mussif07]

Hi everyone,
Since the question is serious, allow me to go straigth to the problem.
I'm modeling a tank with a storage capacity of 100 cubic meters, the inflow of 51 l/s is provided by a constant power pump, while about the same outflow of 50 l/s (180 cubic meters per hour) is drawn by two pipes, each of them leads to the network's downstream zone. Considering one hour time step simulation, in theory, if the inflow falls to zero, the 100 cubic meters volume is not enough to guarantee the fixed outflow. After some hours of simulation the tank is filled and the inflow becomes zero: since the volume storaged is less than 180 cubic meters, the outflow over the next hour should be less than 50 l/s but the results show 0 in the pump and the same outflow as before. Examining the level in the tank, it is not even affected: it is only slightly less than the previous time step but it should be zero.
I have been looking for an explanation for weeks without finding anything and my deadline is approaching so, please help me.

 

[JGard1985]

Can you share/upload you EPA NET file?

Jeff
Pipe Stress Analysis
Finite Element Analysis

http://www.xceed-eng.com

 

[JGard1985]

So.....This better be for work...not a school project, but

1) Water tanks with residence times of <2 hours aren't really that common as reservoirs (drained in no time) and EPANET is having trouble capturing this

2) You need to turn down the timestep to something much less than 1hr to capture the tank/pump relationship.

3) Read the EPANET manual on how to do it, but in short the way I did it was export your network to a text file, then edit the [Hydraulic Timestep] time to something much less than 1 hour, say 5 minutes, SAVE and re-import. I cant find a way to do it in the GUI of EPA NET

Jeff
Pipe Stress Analysis
Finite Element Analysis

http://www.xceed-eng.com

 

[Mussif07]

Thank you JGard1985. I have edited the file because I'm not sure if I'm allowed to share the original project (which replicates an actual aqueduct) so you won't find any town names on the objects and the network has less components, but it still contains the pump in question.
To answer 1): this work started based on a file 10 (maybe 20) years old and my task is to update the network's components to present day, moreover the original file was designed to perform only a steady state simulation, so I think that 100 cubic meters is used as default number just to fill the requested input data but I don't have the actual volume at the moment.
To answer 2) and 3): I can use MIKE URBAN, which is an EPANET based commercial software with a GIS interface and the timestep can be reduced to 5 minutes. As soon as I go back to the PC with the MIKE URBAN's local licence I will upload a screenshot with the results obtained reducing the timestep.
Meantime, if you want, I would be glad to hear an overall judgment over the use of the EPANET's components to represent the water supply network's behaviour (some elements are questionable to my limited experience but I didn't modify the original configuration, surely developed by a more experienced engineer than me...)
Thanks again, have a nice day.

 

[Mussif07]

Not sure the previous post shows the attachment:

https://files.engineering.com/getfile.aspx?folder=5e251348-0994-485a-8005-4c84af842f42&file=0001.inp

https://files.engineering.com/getfile.aspx?folder=ae78231d-5adb-4a6e-9f87-0541f305cd7a&file=0001.net