Conservation of Energy Calculation

When defining the hydraulic grade line, calculations proceed from the system outfall upstream to each of the terminal nodes. For department practice, base calculation of the hydraulic grade line on conservation of energy as shown in Equation 6-22 which includes major and minor energy losses within the system. For conduit, d=1.
EquationObject216237
Equation 6-22.
where:
  • HGL
    us
     = 2 + d = elevation of the hydraulic grade line at upstream node (ft. or m)
  • v
    us
     = upstream velocity (fps or m/s)
  • v
    ds
     = downstream velocity (ft./s or m/s)
  • h
    m
    = minor (junction/node) head loss (ft. or m)
  • h
    f
     = friction head loss (ft. or m)
  • HGL
    ds
     = elevation of hydraulic grade line at downstream node (ft. or m)
  • g
     = 32.2 ft./ s
    2
     or 9.81 m/s
    2
    .