When I run my contour map my model is showing negative pressure at the water plant.
WaterGems
Hello Andrea,
Do you have a junction near the "water plant" that has an elevation set too high? Take a look at a profile of the area to help visualize the hydraulic grade versus elevation. Negative pressure will occur when the hydraulic grade is below the physical elevation. See more here: Troubleshooting negative pressures at pumps, junctions, & other node elements
If this does not help, please provide a copy of the model for review along with a screenshot of what you are seeing: Sharing Hydraulic Model Files on the OpenFlows Forum
Regards,
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
MUD 36AA.wtgpkg.wtgpkg.zip
There's my file please let me know if it works for you.
Yes I received the model.
If you graph pressure at P-1 or P-3 you will see that it becomes negative after around 13 hours. This happens because tank WP-1 GST becomes empty. See the following article for more information on that: What happens when a tank becomes empty or full? (altitude valve)
Your pump controls for this tank seem a bit odd. The pump is on the upstream side (filling the tank), but the controls are set to turn the pump off if the elevation drops. Did you mean to use ">=" for the pump off control and "<=" for the pump on control? If I switch them, the tank does not become empty or full and negative pressure no longer occurs. See more: Troubleshooting Controls in WaterCAD and WaterGEMS
In the calculation options, you have set to report only every 2 hours, so you miss out on seeing a lot of details of the results that happen between. I would suggest changing the Reporting Timestep to "all". This will also reveal that the network becomes unbalanced at times, likely related to the empty tank problem.
I also noticed you have two hydraulically close hydropneumatic tanks downstream of the pump station. I would recommend combining these into one single hydraulically equivalent tank. See more here:
Rapid flow oscillation between hydraulically close tanks
Modeling hydropneumatic tanks in an EPS in WaterGEMS and WaterCAD
do you know by at scenario "2022" p1 show 0 gpm? My "2022 Modified" is showing a gpm now but the other isn't.
Andrea,
The 2022 scenario is configured to run as EPS so the flow changes over time. I assume you are referring to time zero. The reason why the flow in P-1 is zero in that scenario is because the pump "WP-1 Well Pump" is off. That pump is off because your controls are telling it to turn off (there are two controls and both of their conditions are true at time zero because the tank level is exactly 25, and the pump off control takes precedence).
In the "2022 Modified" scenario, the flow is also zero for me for the same reasons (and for all timesteps). I am looking at the model you had previously sent, without making any changes.