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Watergems : finding or calculating actual flow

In watergems , a model is defined with input source as tank and gravity distribution network with junction demand (actual gravity free flow to sump) . After fixing for pipeline diameter and required head at Junction, I wish to find out actual or realistic flow from end junction , as in few nodes, residual head is more than (say 20 to 35 m.)required head as 5 m. I have tried model with Discharge to atmosphere in place of Junction, but not clear with typical flow and pressure drop input. I have gone through various post but not getting proper result. Kindlly suggest/

  • Could you please explain bit more about the issue, are you trying model free outfall at the end?

    If you have already tried the Discharge to Atmosphere Element, best for such situations, what challenges did you face in that?

    If required, you can upload your model files.

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    Regards,

    Sushma Choure

    Bentley Technical Suppport

  • Yes I can send zip file. But before that, my model is simply free outfall at end. First option calculation with average Junction demand. From junction demand run, found residual head at junction end for a particular average flow. As we want to find free outfall flow. tried D2A instead of Junction in second option by putting the value of average flow as a typical flow and residual head as a pressure drop. Is this input data is true for finding free flow or actual field flow?. or we should try hydrant instead of D2A. ?
  • Hello Devang,

    As mentioned is my previous post, discharge to atmosphere is the best option is your case for modeling the free discharge.

    Here is the technote on discharge to atmosphere element.

    http://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/19581.how-does-watergemswatercad-treat-the-discharge-to-atmosphere-element 

    Since you have finalized the head, you should use method 1 to solve for flow to get the maximum flow. 

    Have you tried any of these methods? Do you have any field data since this is an existing system to compare the results with?

    Regards,

    Sushma Choure

    Bentley Technical Suppport

  • Method 1 is a formula for minor loss and gives very less value. say for 1 m/s velocity, H= 0.05. As I know normal water demand, if I treat the same as a typical flow then what will be pressure drop value ?. Is there any connection of 'Hydrant flow curve value' of that junction ? Means that data shows flow vs Head relation. In that case what will be pressure drop value. I understand that difference between Head at zero discharge and Head at Typical flow. Kindly clarify.