In the explanation that the article “Water Model Calibration Tips” wiki à https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/40028/water-model-calibration-tips
There is an article called; “Model Calibration Data: the good , the bad, and the useless”
In that article the following is stated: “The Hazen-Williams equation can be solved for C-factor to give(1)” (p.96)
I understand why the “error” element is introduced since the article is usig the equation to highlight the impact of errors on C factors that might result from calibration. However on the “Bentley WaterGEMS CONNECT Edition Help” website à https://docs.bentley.com/LiveContent/web/Bentley%20WaterGEMS%20SS6-v1/en/GUID-E5FCE3A52CBA40899062D149A5CE2D5A.html
The Hazen Williams equation is described as follows:
Q
=
Discharge in the section (m 3 /s, cfs)
C
Hazen-Williams roughness coefficient (unitless)
A
Flow area (m 2 , ft. 2 )
R
Hydraulic radius (m, ft.)
S
Friction slope (m/m, ft./ft.)
k
Constant (0.85 for SI units, 1.32 for US units).
If I try to isolate for C using this equation I do not see how I get to:
Christen,
I consulted with Dr. Walski about this:
The second equation is the Hazen-Williams equation for an individual pipe.
The first equation represents the head loss for the effective network which includes all of the pipes and their properties. You can think of it as an equivalent pipe between the source and a demand node that behaves like the network. It is not an exact equation but teaches about the relationship between Q, C and h (or S).
The k’s in the two equations are completely different.
See attached.
HW.pdf
Regards,
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
Whit this explanation and the PDF it now makes sense. Thank you.