Advanced rules to control gates in internal SA Connections (2D Mesh)

[Simon A.]

Good evening,

I have built a 2D model of a river that splits in two reaches in HEC-RAS 5.0.3. Water levels upstream of the split are controlled by two dams (see attached image).

I added those dams as internal SA connections inside the 2D mesh. Each of these dams possesses gates that are operated using stop logs. I would like to know if it is possible to apply advanced rules in the unsteady flow file in order to control the gate openings and discharge coefficients. So far, although the detailed output files show that my rules are valid and that the parameters are properly calculated, I cannot apply theses parameters for each gates. The model keeps using the initial values during the entire simulation (see attached .txt file with the rules that I wrote for one of the dams).

Could it be a limitation of using an internal connection to represent those dams? Should I rather divide my 2D area in two separate zones and put separated 2D connections instead?

Best regards,

QC_07_2014.txt

[cameron]

I don’t see why the rules boundary condition would not work inside of 2D unless it is not enabled yet. Is this a model you could share to see if it is set up correctly? You could try a simple test case to see if breaking it up into two different 2D areas fixes it or two 2D areas connected to 1D areas.

[Simon A.]

Hello Cameron,

Because of a confidentiality agreement with our client, I cannot share the model.

The main reason why I wanted to use rules for the dams opening was for setting variable discharge coefficients for each gates. Using Kindsvater and Carter equations, I wanted to calculate the discharge coefficients at every time steps for each gates based on their opening and upstream water level. By checking the detailed output HDF file, I see that the calculation are done properly, but the results are not applied in the geometry.

So far I decided to skip the rules and rather use the Kindsvater equation already available in HEC-RAS for a sharp-crested weir. The only problem is that this method uses a “fixed” crest elevation value for each gate to compute the variable discharge coefficient. The only varying parameter used then is the water level. I understand that HEC still uses gate openings to calculate discharge but I worry that the actual computed discharge does not correspond to reality. The dam system is quite complex and it is used to manage a reservoir that has a volume capacity of trillion cubic meters.

So far the results I obtain using standard equations in HEC-RAS are correct, but I would like to refine the approach I use. I also though using custom rating curves, but discharge is influenced by downstream water levels that can submerge the gates.

Maybe I missed a step when setting my rules? Is there a pointer in the HDF file I could use to see where the computed parameters should apply?

Best regards,

[cameron]

I tested this in a study I am working on and found that the advanced rules do not apply either. I would assume it should work, but this is something that should be brought up with the developers.

[Simon A.]

I also did some further research and I found that advanced rules are not yet supported for a 2D mesh. A user would need to set a 1D structure connected to a 1D reach in order to use them. Maybe it will be possible in a next release?

Thanks for your help!

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