No tailwater effect using a composite outlet structure with a user defined rating

Applies To
Product(s): Bentley SewerGEMS, Bentley CivilStorm
Version(s): 08.11.XX.XX
Environment:
Area: Calculations
Subarea: N\A
Original Author: Mark Pachlhofer, Bentley Technical Support Group

 

Problem Description

I have pond outlet structures that contain user defined rating curves of the flow vs. elevation and during my simulation there is a tailwater effect that causes the water to backup into the pond. I should see forward and reverse flow when I look at the results, but I'm only seeing forward flow. Why?

Resolution

The user defined rating tables in the outlet structure will not account for any tailwater because they assume forward flow only with a free outfall condition. What you will need to do is construct an outlet structure that is equivalent to your user defined rating curve and use that, while making sure the option for forward and reverese flow is set. This will allow SewerGEMS to account for the tailwater effect because you get a family of rating curves when using your outlet structure that account for the forward and reverse flow conditions.

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