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inverse flow direction in watergems

Zeinab Amiri
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Hi

I have a model in watergems. I have asked a question about before. But I have two other questions, which decided to say them in  a new post.

First, as I have taken all the errors, and it seems that all details work correctly, I noticed that the direction of the flow is inverse the one that should be. It means that flow conveys from downstream to the well pumps. What is the reason of it?

Secondly, I replaced my reservoir with a node to balance the amount of flow I desired. Then I gave the demand I wanted from each well to the node right after that well. I have to give some demand to the node which is represented for the supply reservoir in order not to be removed from the model. But the demand is added to the total demand of wells. I gave it a little amount, but I'm not sure if it is true. And the question that does the amount of demand given to the supply reservoir effect on the direction of the flow?

I  upload my model here.

WTG 2K 4W GE NP 435 5.zip

Thanks for your help.

Zeinab 

  • 0 Offline
    Zeinab,

    Your flow is going from J-7 towards J-2 because the only demands that you have in your model that need to be met are on the junctions just downstream of the pumps in your model. The flow will therefore travel to just those junctions in order to fulfill the demands because WaterCAD is a demand driven program, which means that all demands must be satisfied. To put it very basically, if you don't have demands in one section or branch of your model and there is no need for water to flow through it to supply a demand somewhere else you will not get flow through that section of the model. If you want to see the flow go from J-7 to J-21 then you will need to place a demand on J-21. I placed a demand of 75 L/s on J-21 because that's the demand you had on the other junctions and if you do the same you'll see how the flow reverses direction to fulfill that demand.

    Regards,
    Mark

    Mark

    Answer Verified By: Zeinab Amiri 

  • 0 Offline in reply to MPachlhofer
    Hi Mark
    Yes, I placed the demand to the J-21 and I get the result. As an explanation I want to say you that I have a supply reservoir on J-25. In fact it is a reservoir that I have changed it to a junction because I had extra flow after the pumps.
    (And I want to extract ( draw out) the amount of water equal to the demand in each joint from the well before. )
    So by these explanation, is my model correct?

    Thanks
    Zeinab
  • 0 Offline in reply to Zeinab Amiri
    Zeinab,

    I'm not sure what you mean by extra flow after the pumps. Maybe if you could describe this in more detail using labels of elements in your model and the exact values that you are getting vs. what you expect to get I can have a further looks at the issue. I think part of your confusion in this case might be with how pumps work in WaterGEMS. I've included a link below that explains this:

    communities.bentley.com/.../20867.how-do-pumps-work-in-the-hydraulics-and-hydrology-products

    It would also help me if you could put this statement, "(And I want to extract ( draw out) the amount of water equal to the demand in each joint from the well before.", into other words because I'm still having trouble trying to understand what you're looking to do.

    Regards,
    Mark

    Mark

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