I'm modeling a residential storm sewer system in StormCAD. Most of the inlets are "On Grade" and a "Conventional" gutter shape with a maximum depth of 6-in has been included between them to account for any overflowing.
The problem I have is that when the inlet results indicate that there is overflowing, no flow is reported at the gutter downstream of "overflowed inlet"
Hello Jose,
Gutters will accept bypass flow, but not overflows. If you need to model overflows going into the gutter, you would need to model this using CivilStorm or SewerGEMS and the Explicit solver, as detailed here.
If you have seeing overflows at the catch basin, that is a sign that the system is undersized. You would want to look into sizing the pipes or making other adjustments to system so that the overflows do not occur.
Regards,
Scott
Hello Scott,
I understand that the overflow results should be a sign of a system undersize. Actually, I increased the pipe size and resolve the "overflowing". But now I just got a bit of confuse on how stormcad perform the calculation vs what happen in "real life".
Under what conditions the model recognizes a bypass flow? In this case, the pipes are undersized. But what if the runoff at a given storm event is higher than the inlet capacity, Should it be able to recognize the "bypass flow" into the next inlet?
Jose,
Bypass flow is gutter flow that is not captured by an inlet, so it continues traveling down the gutter to the next inlet. So, this is a surface (inlet/gutter) network concept. StormCAD does not have interaction between the surface network and the subsurface (conduit) network. As Scott mentioned, you would need to use CivilStorm or SewerGEMS for this, because StormCAD is focused on designing networks to not flood. You can read more about flooding/overflow limitations with StormCAD here: Why is the HGL reset to rim elevation for flooded structures?
José Díaz said:But what if the runoff at a given storm event is higher than the inlet capacity, Should it be able to recognize the "bypass flow" into the next inlet?
Per the above, flow that cannot be captured by an inlet becomes bypass flow and travels down the downstream gutter to approach the next inlet. When using a catalog inlet, StormCAD uses the HEC-22 methodology for inlet capture calculations to determine the capture efficiency (percentage of approach flow that is captured) for the given inlet parameters.
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.