[Chris G.]

Just a quick head’s up that there is a nice presentation on the use of Rules posted at RASModel.com. http://hecrasmodel.blogspot.com/2013/09/advanced-rules-for-unsteady-flow.html

Enjoy!

Chris
@RASModel

[Chris G.]

Hi Pallo-

Dr. Michael Gee was kind enough to share this presentation written by Mr. Steven Piper of HEC that discusses in detail the use of Rules for inline structures and gates in unsteady flow.

http://hecrasmodel.blogspot.com/2013/09/advanced-rules-for-unsteady-flow.html

[Chris G.]

Unfortunately there is no “global” tool to do this in RAS. If you have some programming skill, you could easily create a program to read in the geometry text file and change all stationing values for station/elevation points by 10,000.

However, by the time you write that program, you could probably have manually adjusted each cross section one at a time using the Options…Adjust Stations menu item in the cross section editor.

Probably the best thing to do is find an intern and set him/her loose on this.

Good luck-
Chris G.
@RASModel

[Chris G.]

I’ve found the best way to do this is:
1. Generate a rating curve that describes the head/discharge relationship for the drop inlet structure for all expected stages.
2. Add a dummy gate in an inline structure. The invert of the gate should be the same as the crest elevation of your drop inlet structure. Gate size is irrelavant.
3. For the gate type, use “User Defined Curves”.
4. Pick an arbitrary gate opening and then assign your rating curve to that gate opening.
5. In the boundary conditions editor, use T.S. Gate Openings as the boundary condition type and assign that same gate opening for the entire simulation to the dummy gate you just made.

There you go. I’ve done this many times for morning glory spillways and other drop-inlet types structures and it works like a charm.

Good luck-
Chris G.
@RASModel

[Chris G.]

It’s really a judgement call on your part. Ideally you’ve been out to your river and have seen it at relatively high flow. But most of the time we don’t have that luxury. So you need to use your knowledge and experience on how water moves through river systems. Draw flow lines that capture your perception of how water will move through the system at high flow. Then draw your cross sections so that they are perpendicular at all locations to the flow lines (this will most likely require doglegging them). Please review this:

http://hecrasmodel.blogspot.com/2012/07/how-to-draw-cross-sections.html

Good luck-
Chris G.
@RASModel

[Chris G.]

I don’t think you’ll find anything out there better than chapter 16 of Version 4.1 Users Manual.

[Chris G.]

I’ve noticed that before as well. Remember that hydraulic transients are dynamic and the flood wave travels very fast through your canal (gh)^0.5. A depth of 3 meters gives a wave celerity of about 5.5 m/s. If your time step and detailed output intervals are very coarse and/or your canal length is relatively short, you may not notice a traveling wave at all when you animate in HEC-RAS. I’ve played around with this in the past, and by making the canal very long, using a fine time step and especially a small detailed output interval, and closing the gate very fast, you see a very well-defined wave traveling in the upstream direction. I can send you an example HEC-RAS project if you leave me your email.

Chris G.
@RASModel

[Chris G.]

I would encourage you to leave the ineffective flow areas in, if you believe they are indeed ineffective flow areas. As pointed out above, you should expect to see a local decrease in water surface elevation through a constriction (at the cross section with the ineffective flow areas). The water surface rise I think you are expecting to see will happen upstream of the constricted cross section. That is where the energy loss through the constriction manifests itself as a higher water surface. Leave the ineffective flow areas in there and then compare the with and without project profiles for a few cross sections UPSTREAM of the constriction. I bet you’ll see an increase in water surface elevation (a backwater effect) from the proposed design with ineffective flow areas.

Good Luck
Chris
@RASModel

[Chris G.]

Try looking at the internal bridge cross sections, see if you see something there. Or you can open the geometry file in a text editor (Wordpad, Notepad, etc.) and then search for the station/elevation points listed in the error message. That might show you where the offense is taking place.

If that doesn’t work, try deleting 94.1 and re-entering it.

Good Luck-
Chris
@RASModel

[Chris G.]

I’d say keep pressure flow. Try both and see which gives you the highest energy answer.

Good Luck-

Chris
@RASModel

[Chris G.]

I get that message occasionally when working in DSS and I’m right with you-it’s frustrating. That’s about the time I usually copy and paste out of DSS-VUE directly into the gate setting editor.

Good Luck

Chris
@RASModel

[Chris G.]

In the GIS Export window, there’s Additional Properties located in the lower right-hand corner where you can select Levees and Ineffective Areas. Hopefully that will help.

Good Luck

Chris
@RASModel

[Chris G.]

Go into my stable and take my finest stallion. He’s yours.

You’re welcome!

[Chris G.]

Digitizing flow lines in ArcGIS will allow HEC-GeoRAS to automatically calculate reach lengths for you. They will come into RAS when you import your GIS import file. If you don’t have access to GeoRAS, then I’m afraid you have to enter in the reach lengths manually.

Good luck.

Chris
@RASModel

[Chris G.]

That’s a bug. You should send it to HEC using their bug report. http://www.hec.usace.army.mil/software/hec-ras/bug_report.aspx

In the meantime, double check that you’ve entered in all of the required data, the data makes sense, and that you have your Windows International settings set to English (United States).

Good luck.

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