Hello Bentley,
Why is it hard to control flow in an open system? I am getting undesired flow from the reservoir to the tank however how much I specify the demand at different nodes. I don't want to use a flow control valve since it adds excessive/abnormal head to my model not a similar case in the real life scenario since the position of the flow control valve is right at the intake structure /weir. My worry is that I Fear it might have less to near NO effects unlike it has been exaggerated.
see the attached .how can I cure this?
Hello Mulongo,
How much flow do you expect to be going into the tank?
I recommend modeling the actual system as accurately as you can. If there are demands and a flow control valve then include them in the model.
When I opened the model there weren't any demands applied. After computing, there was 28 l/s going into the tank. The lowest pressure was about -28.6 mH2O.
After applying a demand of 0.2 l/s at each junction (about 20 l/s total) there was 17 l/s flowing into the tank. However, the lowest pressure was about -40 mH20.
Then I added a flow control valve next to the tank and limited the flow to 10 l/s. The lowest pressure was about -20 and the highest pressure was about -20.
Regards,
Craig Calvin
Bentley Technical Support
Thank you Craig for your time,
I want to achieve a flow of not more than 20l/ s, a flow that is enough to enable me to avoid any negative pressure at any junction .I tried to apply a demand of about 20l/s at the tank and the node next to the tank but the flow in both cases still remains 28l/s. How can I achieve a flow of not more than 20l/s without using the FCV since in real situation the FCV doesn't have direct effects to the pipeline since it will be positioned just at the reservoir
Flow can move by gravity based on boundary condition HGL differences. When you don't apply any demands the headloss is what restricts the flow. Using an FCV would be another way to restrict flow, but you can't use one.
Another option would be to reduce the pipes' diameters or increase the roughness.