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A
afarias1-Visitor
1-Visitor
May 14, 2015
Question

Gradually-varied flow: backwater calculations

  • May 14, 2015
  • 3 replies
  • 2956 views

Dear Friends, I need to make a hydraulic profile of a channel. In which a control section is a free fall downstream of it. Use the software to little more than two months and do not have much skill with it. I'm trying to resolve the EDO (dx / dy = (IJ) / (1-Fr²), but I am not succeeding because an error appears in which I do not know identify. Attached hereto the file to anyone who can help me. Thanks in advance!

Anderson Farias

3 replies

V
24-Ruby III
VladimirN24-Ruby III
24-Ruby III
May 15, 2015

Hi,

I do not see any error messages in your document. Using Mathcad Prime 3.1.

R
RichardJ19-Tanzanite
19-Tanzanite
May 15, 2015

I also don't see any error, using Prime 3.0.

V
24-Ruby III
VladimirN24-Ruby III
24-Ruby III
May 18, 2015

It is possible that the user is not satisfied with the mathematical model for their calculations.

R
RichardJ19-Tanzanite
19-Tanzanite
May 18, 2015

Maybe. We have to wait for clarification.

A
afarias1-VisitorAuthor
1-Visitor
May 18, 2015

Dear Richard and Vladimir, I apologize for not having specified the right problem.

It happens when I insert the value to 0 mH, or consider a section of rectangular and not trapezoidal channel, is where the problem arises.

The important fact to be reported is that when I make the validation of my calculation model with the HEC-RAS software, which uses the same calculation methodology, the figures do not match.

I thank you help!

AF

R
RichardJ19-Tanzanite
19-Tanzanite
May 18, 2015

It happens when I insert the value to 0 mH, or consider a section of rectangular and not trapezoidal channel, is where the problem arises.

Do you mean 0 m_sub_h? I don't get any error if I insert 0 for that variable.

How do you define it to be rectangular rather than trapezoidal?

The important fact to be reported is that when I make the validation of my calculation model with the HEC-RAS software, which uses the same calculation methodology, the figures do not match.

So what is the answer supposed to be?

Where does the equation come from? If you get a different answer, then you are doing something differently. The first thing to check is the equation. Also check the units for the Manning number (which is not unitless)

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