We have a composite system for storm water network(see below screenshot)
I would like to model an overflow pipe(see below screen shot) by considering a start control structure at the outlet pipe.
My question is, What is the best type of control structure to model an overflow pipe with a vertical drop?
Mohthesham,
Can you clarify where the overflow pipe is? See below comment in red:
As water first reaches the overflow pipe, it may "spill" into it and act as weir flow, and then when the depth is high enough it would act as orifice flow. However, it may be acceptable to simply assume orifice flow and model the conduit control structure as an orifice with the Orifice Type set to Bottom Orifice. See more here: Using Start and Stop Control Structures for conduits and channels
Regards,
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
Answer Verified By: Mohthesham Mohammed
Thanks Jesse,
Your interpretation of the system is very right.
I have modelled using the pipe control structure as a weir type thinking the results will be conservative in nature when compared to real time flow rates in pipes.However, authority as commented that the pipe control structure in our case cannot be wier type.
I will change it to orifice type now and recheck.
Thanks a lot again.
regards,
Mohthesham Hussain Mohammed
Hi Jesse,
Good day!
In continuation to the above, please see the below screenshot for the results in one of the branches. The overflow pipe drops are now modelled as orifice(bottom outlet).
Appreciate, if you can elaborate on if the behavior of HGL and EGL are normal. How is it possible for the HGL rise above the EGL?
Which product and solver are you using? For example the GVF-Rational (StormCAD) solver, or the Implicit or explicit (SWMM) dynamic solver in SewerGEMS.
If you're using the Implicit or Explicit solver, ensure that the continuity error is low (see troubleshooting here and here), ensure you are looking beyond time zero (use the Time Browser to advance forward in time) and try setting the "Output Options" field for your conduits to "Detailed Results".
If this does not help, please provide a copy of the model for review along with steps to reproduce: Sharing Hydraulic Model Files on the OpenFlows Forum
Modelling the overflow pipe with start control structure set to orifice(bottom outlet) is giving unfavorable results for HGL as per our trailing discussion.
However, we have got acceptable results when we set the same to weir(v-notch 60 deg.) plus allowing it to use orifice equation when surcharged.
My question is , how to ensure the width of weir is more or less equal to the overflow pipe rather than the software considering it to be full width of the chamber? Can it be justified with the angle of the V-notch as per below screenshot?
Appreciate your expertise support!