AutoCAD Civil 3D - Stormwater

AutoCAD Civil 3D - Stormwater

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cfarrow
Posts: 17
Registered: ‎06-08-2012
Message 1 of 4 (485 Views)

Inlet Bypass & Street Section Modeling

485 Views, 3 Replies
06-27-2012 02:58 PM

We recently began experimenting with SSA and are trying to verify the inlet calculations that were done in excel to make sure we understand the software before putting it into everyday use. We've created a custom parabolic street section and applied it to the bypass links, and as far as that aspect goes, we understand it and it's all working great.

 

Our issues come in figuring out how to model inlets directly across from each other in a street section. The issues arise when the top width (of Inlet 1, in the attached graphic, for example) exceeds the half section width and flows over the crown into the opposite side of the street (to Inlet 2, in attached graphic).

 

Any suggestions? We have tried weirs and flow diversions to no avail. Attached is an example of what I'm trying to explain. Inlets 1 and 2 are opposite from each other, and both connect into a MH labeled SD-J 29+33.00. Link-05 connects to the next downstream MH, and there are 2 links that follow the gutter lines to the North used as bypass links from Inlets 1 & 2.

 

Thanks,

 

Clayton Farrow

Clayton Farrow
Civil 3D 2014
Windows 7 Professional
Intel Xeon E31270 @ 3.4 GHz
8 GB, 64-bit
Employee
Matt.Anderson
Posts: 2,909
Registered: ‎05-13-2005
Message 2 of 4 (474 Views)

Re: Inlet Bypass & Street Section Modeling

06-28-2012 05:42 AM in reply to: cfarrow

Clayton -

 

Unfortunately, only a single surface outlet from an inlet is allowed. There would be no implied connectivity between the inlets.

 

From your description, Inlet-1's depth is large enought to that the spread exceeds 1/2 of the street width.   I would likely swap the inlet for two junctions, one that models the surface connection together with a lower manhole junction.  Between the surface junction and the manhole, I would add an orifice with the dimensions of the inlet structure, and then model the surface connections between the downstream structure and Inlet-2.

Matthew Anderson, PE
Product Manager
Contributor
cfarrow
Posts: 17
Registered: ‎06-08-2012
Message 3 of 4 (470 Views)

Re: Inlet Bypass & Street Section Modeling

06-28-2012 06:14 AM in reply to: Matt.Anderson

Matt,

 

Thanks for your prompt reply. That was the answer I was expecting but not hoping to receive. I'll see if I can make it work, but I'd like the two inlets to be able to "interact" to know which would be overflowing the crown instead of having to know that from the outset.

 

 

Clayton Farrow

Clayton Farrow
Civil 3D 2014
Windows 7 Professional
Intel Xeon E31270 @ 3.4 GHz
8 GB, 64-bit
*Pro
fcernst
Posts: 1,170
Registered: ‎01-07-2011
Message 4 of 4 (305 Views)

Re: Inlet Bypass & Street Section Modeling

11-27-2012 07:30 PM in reply to: cfarrow

The only problem with an orifice as suggested is that it doesn't account for dynamic trajectory flow  parameters that a rating curve built from proprietary inlet calculations would provide if these inlets are on-grade.

 

I would use two storage nodes connected with a weir to model flows back and forth across the crown, and inlet rating curves implemented in Outlet connections with flap gates closed connected to the lower nodes for the pipes, and orifices between the lower nodes and inlet storage nodes to model the possible flow reversals.

 

 

Fred Ernst, PE
C3D 2015 SP2
Ernst Engineering
www.ernstengineering.com
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