Comparison of the H2OMAP SWMM Hazen Williams Force Main Solution to a Steady State HW Solution

Note:  Comparison of the H2OMAP SWMM Hazen Williams Force Main Solution to a Steady State HW Solution

Comparison of the H2OMAP SWMM5 Hazen Williams Force Main Solution to a HW Solution

by dickinsonre
Note:  Comparison of the H2OMAP SWMM Hazen Williams Force Main Solution to a HW Solution 
In this example, we compare the force main head loss in four links in H20Map SWMM to the head loss in a steady state HazenWilliams solution for the same length pipe, diameter and flow (Figure 1).  The H2OMap SWMM model has a large constant dry weather inflow at the wet wells which floods the wet well and causes a constant pump flow to the force main (Figure 2).  TheHW calculator is located here http://www.engineeringtoolbox.com/william-hazens-equation-d_645.html and a comparison forHW head loss in PSI for 5000 feet long, 3 inch diameter pipes with HW Coefficients of 130, 120, 110 and 100, respectively, is shown in Table 1.   The SWMM 5 equation loss (PSI Diff) and the PSI loss from the HW calculator are very close for all four links.  
Table 1.  Steady State comparison between HW Calculator and H2OMAP SWMM/SWMM 5 Force Main calculations. 
HW
SWMM5
SWMM5
SWMM5 Loss
Loss 
Coefficient
Psi UP
PSI Dn
PSI Diff
PSI HW Calculator
130
84.563
44.88
39.683
39.82
120
88.772
43.765
45.007
45.16
110
91.798
41.426
50.372
50.54
100
95.354
38.727
56.627
56.82

 Figure 1.   H2OMAP SWMM Wet Well, Pump, Force Main and Gravity Main Network 
Figure 2.  Constant Pump Flows
 


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