EPANET Total Head of Junction

Question

EPANET Total Head of Junction

kc27315 (Civil/Environmental)

(OP)

13 Mar 18 19:10

Considering Bernoulli's Equation, the Total Head should be the sum of the Elevation/Velocity/Pressure Heads at each point. My EPANET question is this: Is Velocity Head included in the computation of "Total Head" at a given Node? If so, which velocity is used? One of the upstream velocities? A downstream velocity? Average of those? Also, if it doesn't include velocity head, why not?

I've attached an example screen shot, and running a quick calculation shows that 4552+77.88*2.31 ≈ 4731.9 which is very close to 4731.73 ft of total head, so I'm imagining that maybe the Total Head doesn't include velocity head...

Hopefully I'm asking this in the right place. If not, I apologize and please delete.

Thank You!!

http://files.engineering.com/getfile.aspx?folder=d5d98709-4de2-4f57-8472-74

coloeng (Civil/Environmental) · Answer 1 · 2018-03-15 15:10:16

Velocity head is not usually included. It is usually fairly insignificant in a typical distribution system.

kc27315 (Civil/Environmental) · Answer 2 · 2018-03-15 15:16:05

Gocha, thanks for the reply coloeng! I guess looking at, say, a V = 10 ft/s would yield a velocity head of only (10^2)/(2*32.2) ≈ 1.55 ft => 3.59 psi, which isn't a ton of pressure I suppose... And perhaps by not including it, we would have conservative results. Thoughts anyone?

coloeng (Civil/Environmental) · Answer 3 · 2018-03-16 14:12:33

10 ft/s actually only gets you 0.67 psi. Also, 10 ft/s is awfully high for a typical distribution system.

cvg (Civil/Environmental) · Answer 4 · 2018-03-16 15:34:21

to convert feet of head to pressure in psi, you need to divide by 2.31 not multiply. that will solve a lot of your issues

kc27315 (Civil/Environmental) · Answer 5 · 2018-03-16 20:15:57

cvg, that's correct. PSI = Feet of Head divided by 2.31,

however, in my case, I'm converting in the other direction. 77.88 PSI, when converted, is 179.9 feet of head.

This makes my equation: 4552 ft + 179.9 ft = 4731.9 ft

Units can definitely be a bugger sometimes though. I mix them up more often than I'd like to admit!

Come Join Us!

Posting Guidelines

Related Projects

Jobs

EPANET Total Head of Junction