Dear Bentley,
1-reservoir - pump - network (has only junctions)
1-reservoir - pump - network (has junctions and tank as this example)
1-reservoir - pump - network (has junctions and reservoir)
Mohamad Azzam,
Basically we force a flow through the pump and we see what the difference in head will be. We repeat for multiple points to get a curve.
We have a paper coming out soon in the Journal AWWA to explain how things work for dead end systems (no discharge side tank or reservoir).
The curve will be concave downward when the flow is out of the discharge side tank/reservoir (demand exceeds pump flow). As the pump flow increases, the flow will be into the tank and the curve will become concve upward as you would expect.
Dr.Tom,
Thanks for reply, but at the mean time I did not get the point clear, usually when I use the program when I have forcemain design and lift station, the program give wonderful results and curve, here in this example how is the Static head calculated? and I mentioned three cases; two of them has reservoir and tank as discharge points, what about them? or at the mean time is there a way to do the system curve as required.
Please may you inform me when paper published in Journal AWWA or email me with copy of that paper.
Mohamd Azzam,
The system head curve is correct and the shape is what it is. You only get the shape that you expect when there is no water use along the way between the pump and the tank/outlet (as in a sewer force main).
When you have water use, the shape changes. See the paper
“Developing System Head Curves for Water Distribution Systems,” Journal AWWA, Vol. 81, No. 7,
July 1989 (Lindell Ormsbee and Tom Walski)
Mohamad,
See also this discussion thread for some more information about system head curves: http://communities.bentley.com/products/hydraulics___hydrology/f/5925/p/14911/98166.aspx
Regards,
Mal
Hi Mal,
I had read all discussion you mentioned and was great answers, in that discussion (pumping to high point) I would to ask the question in different way as follow:
the pump is filling the tank and we have negative pressure before the tank?? the understanding if you have negative pressure that means the flow does not reach to that point; so how is the flow reaches to the tank?? (many engineers I had met before asking about that case as I explained), please advise.