SSA - Inlet Bypass

[jmiller0621]

I have a project using several curb inlets on grade with the associated road bypass links as well.  The bypass links were set at the elevation of the invert of the curb inlet opening.

In reviewing the results, I often find the situation where my inlet results say that (for example) 0.5 cfs has bypassed the inlet.  However, looking at the Bypass results, significantly less shows up (about 0.2 cfs).

I have tried adjusting my lengthening timesteps for the hydrodynamic flow, changed my user-defined cross section to a pipe, lowered the bypass inverts to be equal with the sump bottom, etc. but I always get the same result where my results from the two sections don't come close to matching.  Could this be a result of my short TOCs (all about 5 minutes due to the flow just being on a road section?)

Unfortunately, I can't post my model on here as the .spf file extension isn't allowed.  However, could anyone comment on my basic setup or be willing to take a quick look at my model?

Thanks

Jesse

[DBRay]

Hi Jesse,

You mentioned that you connected at the invert elevations of the respective inlets. But, bypass links represents the roadway so in my opinion they all should be connected at the rim elevation of the respective inlets. You could make the changes accordingly in your model to check the results.

Also, if you are not using Rational, Modified Rational or DeKalb Rational as your hydrology method then you may want to make the reporting and routing time steps equal under Analysis Options dialog.

Thank you,

Debajit

[jmiller0621]

Hi Debajit

Apologies for not being clear about this before... I did connect the bypass at the rim elevations.  I then proceeded to try different elevations and link configurations to see if that made a difference.

Regarding methodolgy, I am using Rational Method with hydrodynamic routing.  I did a lengthening time step of 10 seconds to stabilize the model in other links, but no matter what I try, I can never get the inlet bypass result to match the actual flow in the bypass link.

I don't believe that we can adjust the Routing Time Steps in the Rational method as that area is grayed out.  I think that must be the issue though as the 30 second time step is probably missing the peak flow passing through the Bypass link.

any other thoughts?

Thanks

Jesse

[DBRay]

Hi Jesse,

I could take a quick look at the model if I would be able to help you. If you don't mind, you could send the project file at debajit@bossintl.com.

Thank you,

Debajit

[clemk]

Jesse.  To get around the problem with posting the SPF file, you can ZIP the file and post that.

[Matt.Anderson]

Jesse -

Feel free either to compress the SPF file and post it as a Zip file and attached it to the discussion group or drop me or Debajit an email.

matt dot anderson at autodesk dot com

[jmiller0621]

Thanks for the tip regarding the .zip .... hadn't thought of that!  I have passed the .spf file to Debajit by separate email.  Thanks for your help.