Hi
I am modeling a sewer project and there is only one path for the Sewage Force-main. there is a high point in the middle of the path for direct pumping from Wet Well W-7 to Manhole Su-MH-1354 and there was a negative pressure at the high point , so I suggested to put pressure breaker tank Wet Well "W-20" , to overcome the negative pressures My Questions as follows:-
1- is there any other solution than using W-20 wet well ??
2- How to control the outlet flow from Wet well W-20 (2,915.5 m3/d) to be the same as pumped flow to the wet well W-20 (891.7 m3/d), I know that the outlet flow from wet well is based on static head and downstream forcemain size , but is there any way to control, because actually the flow which will enter to W-20 is 891.7 m3/d not 2,915.5 m3/d
Hydraulic model attached in below link
https://we.tl/t-uISz3GDFVr
Regards
Sayed Ali
Thanks Jesse, the article you mentioned explains the issue well
Many Thanks to all
I suspect you are seeing the negative pressure in profile view and are concerned that is predicting column separation. As seen in this article, the negative pressure on the downstream side of an open air valve in profile view with the GVF-Convex solver can be interpreted as the part-full flow.
If by "solve the problem completely" you mean something else, please provide further screenshots and/or a copy of the model.
Regards,
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
Answer Verified By: Sayed Elhagr
If you have an air valve at the high point you will not have column separation. You will get air into the pipe which is different from column separation where the water vaporizes. Air and water vapor are very different.
The GVF solver for pressure pipes assumes the pipe will flow full. When you report negative pressure and you have an air valve, the interpretation is that the flow down the pipe is less that what it would take to fill the pipe.
Larry
Thanks for your answer, my question that I provided one air valve and it does not solve the problem completely, so what is the solution rather tan converting the downstream pipe to gravity pipe
Thanks
Sayed
I did not get what you mean by there is no negative pressure in GVF solver, can you explain this point more?
What I understand that when pump will start flow will reach the high point and then water column separation will happen and vacuum will happen at these high point and this the reason why we adding double acting air valve so when pipe line is filling accumulated air will be released and a water column separation will happen air will enter the pipeline to overcome vacuum condition