EGL OUT higher than EGL IN

Hello Steve,

In the profile PDF you sent, the EGL appears to be increasing as you move upstream - 106.05 < 106.73 < 106.85.

Are you referring to the "jump" seen in the EGL across CB-5? This could be related to an increase in velocity head between the two pipes. What is the flow profile showing as for both pipes? (M2, S2, etc) It looks like it may not be the case, but if there are two hydraulically steep pipes in series, you can see a discontinuity because of the interruption from two consecutive frontwater analysis as explained here:

Hydraulic grade discontinuity at steep pipes or across nodes (frontwater analysis)

Also, from the help topic "Energy Discontinuity",

"The program by default uses hydraulic grade as the basis for its hydraulic computations. Energy grade at any given point is then computed by adding the velocity head to the hydraulic grade. Because of this standard practice, energy discontinuities may occasionally occur, such as when pipe size decreases in the downstream direction, or pipe slope increases."

For information on the impact of the structure loss mode (EGL vs HGL), see this article:

What is the difference between the Hydraulic Grade and Energy Grade 'Structure Loss' calculation option?

If this does not help, please send a copy of the model files (.STSW and .STSW.SQLITE, zipped), per the following article. With the model file, a more specific answer can be provided.

Sharing Hydraulic Model Files on the Haestad Forum

Bentley Help.stsw_1_175.zipJesse, thank you for the reply.

Yes, the EGL discrepancy I was referring to was at CB-4.  I would have expected the EGL always increase here. The flow profile for CO-105 is M1 and for CO-104 it is M2.  I have also included the model here with this reply.  I am having the same problem at CB-1 and CB-2.  CO-103 also has an odd HGL and EGL profile.  

Thank you again for your help!

Hello Steve,

Thanks for sending the files. This situation is addressed in the "Energy Discontinuity" help topic that I previously mentioned and related wiki article. If you look at the Velocity Head result for the two pipes adjacent to CB-4, you will see that it increases as you move downstream.

Because the program defaults to basing the calculations on hydraulic grade, an energy discontinuity can occur like in the case you cited. If you change the "Structure Loss Mode" calculation option to "Energy grade", the discontinuity in EGL will no longer occur, but there's a chance you could experience HGL discontinuity.

Structure Loss Mode = Energy Grade: