In SewerGEMS, we are having a scenario were we are designing a Sewage Pump Station for a new Development, that will pump INTO a sewage storage tank. From this Sewage Storage tank, we will have flows regulated; because the downstream local Municipality's Sewage Pumping Station can only allow so much flow. For my Storage Tank, I used a Pond. for outlet, I was using a Vortex Valve. I am trying to set the flow out of pond to a constant flow rate. I would I accomplish this with the Outlet Structure? Is vortex Valve best choice for Model?
Jason Grimm
Jason Grimm, PE
Jason, you could model storage either with the wetwell element or a pond. With the wetwell, outflow would be controlled either by the hydraulics of the downstream pipe, a weir or orifice control structure placed on that conduit, or with a pump. So for example you could model it as wetwell > pressure pipe > pump > pressure pipe > outfall (or manhole > conduits), with the pump's pump definition configured to produce a constant desired flow.
Or, you could use the Depth-Flow option with a conduit control structure on a conduit downstream of the wetwell.
The pond element is the third approach, where you can use a composite outlet structure with a user defined rating table as Scott mentioned. With the user defined rating table, you can specify the exact flow for each pond water surface elevation. So, you could specify a constant outflow for the whole range of pond elevations, to achieve a constant outflow.
Regards,
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
Jesse
Currently, I have the following order in the Model;
1. Wet well (represent Pump's wet well)
2. Pressure pipe (suction piping of pump)
3. Pump
4. Pressure pipe (discharge piping of pump)
5. Conduit (inflow pipe to outlet structure)
6. Oufall structure
7. Pond
8. Outlet Structure
9. conduit.
This option, I would need to set the defined rating table
If I use a wet well, I want to do the following order (upstream to downstream)
5. Manhole (represent the elevation change from pump wet well to pipe before it enters storage tank)
6. Conduit (inflow pipe to sewage storage tank)
7 Second Wet Well (represent sewage storage tank)
8. Conduit
Two questions with this arrangement. Do I need an Outfall after my Pump Station wet well (before second wet well)? Does the wet well beingused as storage tank need an orifice control?
Jason
Hello Jason,
It is not necessary in case of second wet well to have outfall before it, you can just end the network with an outfall though like in below screenshot.
About orifice control for the second wet well, as mentioned by Jesse in his reply, with the wetwell, outflow would be controlled either by the hydraulics of the downstream pipe, a weir or orifice control structure placed on that conduit, or with a pump. So in this case you could try by placing a conduit control structure on conduit downstream of the wetwell and see how it responds.
Sushma Choure
Bentley Technical Suppport
If I do not add a "second outfall" before the Sewage Storage Tank (My second wet well), I get the following error:
"Gravity sub-network has more than one outfall or wet-well. Run query "Find subnetwork with more than one outfall"." Hydraulic Results
If I add a second outfall before my second wet well, I get the following message:
How do I get the model to run without one of these two error messages?
You must be using the GVF-Rational solver which is not capable of solving networks where one or more gravity subnetwork is connected to more than one outfall. This is documented in the below wiki article;
How to resolve the user notification: Gravity sub-network has more than one outfall or wet-well
You can try using our dynamic solvers such as Implicit or Explicit SWMM solvers which are capable of handling such situations.
As Sushma has suggested rather than simulating storage with a pond or a second wetwell, you can simply try using a conduit control structure which can regulate the flow downstream towards the outfall.
Another option is to have two separate subnetworks. This would mean you would have to end the first one at an outfall and then have a separate subnetwork beginning with the second wetwell and ending with a second outfall. Please ensure that both these are not connected with one another in any way. Now after solving initially observe the flow vs time relationship at the first outfall and use this as an input to the second wetwell. This way you can analyze for your system.
Yashodhan Joshi