Hydraulic Grade Line Calcualtion 1

[marthab]

I was asked to furnish hydraulic grade line calculations for a system of 4 pipes that go from CB to CB. I created a spreadsheet, but I am getting for my last 2 pipes (upstream) the E.G is lower than the invert of the pipe. Is that possible? Also, does anybody know of a spreadsheet that is already developed for this?

 

[gbam]

marthab- mathematically it is possible to achieve an EGL below invert. That only means that the pressurized system analysis (I assume you used that) becomes unsealed. You now need to evaluate based on open channel flow. If you have not read through FHWA's HEC22, I recommend that you download and follow the procedure within.

The process is relatively straight forward to code within a spreadsheet. There are a number software packages that use the HEC22 procedure.

Free -- EPA SWMM 5.0, Demos of fee based software.

$$$$ -- Stormcad, Inroads Storm & Sanitary, Hydraflow, HYDROCAD to name a few.

Goodluck.

 

[Drew08]

Energy = Invert elevation + Depth + Velocity Head.

Depth and Velocity are either positive or zero, so it is not possible for energy grade to be below the invert.