Cress Help - Flow - Flow and structures - A15.2

Gate structures 

Discharge

        (equation 1)

Generally

                                    (equation 2)

 

In which:

  • b = width of the spillway or gate [m]
  • g = acceleration of gravity = 9.81 [m/s2]
  • Dd = sill height [m]
  • He = upstream energy level [m]
  • hdstr = downstream water level of spillway [m]
  • hupstr = upstream water level [m]
  • hs = dimension of opening under the gate [m]
  • Q = rate of discharge [m3/s]
  • uupstr = average rate of flow upstream [m/s]
  • m = discharge coefficient or contraction coefficient [-]

The energy level, water levels and sill heights are determined in relation to a horizontal reference level.

It should be noted that the equations are based on the law of Bernoulli and thus are only valid if the friction and inertial losses play a subordinate role. In practice this means that there must be a question of a significant hydraulic gradient (ord 0.1 m) over the structure.