Sluice Gate

Remember that a sluice gate can be used upstream of a channel, or somewhere in between a channel.

For a frontwater curve:

• if hup=0, the discharge Q must be given (the discharge Q will be used here interchangeably for the mass flow $\dot{m}$; the ratio is the constant density $\rho$). For the gate height (ha) one can determine hup.
• else if hup $>$ 0 and Q=0, the discharge can be calculated from hup and ha.
• else either hup $>$ 0 and consequently Q $\ne$ 0 or hup $<$0. In the latter case the sluice gate must be somewhere in the middle of the channel and Q will be known. So Q is known at any rate and hup is determined based on Q and ha.

For a backwater curve:

• if hup is a boundary condition Q* can be calculated based on hup, hdo and ha (hdo is known since the curve is a backwater curve). If this value matches the value Q used for the backwater curve the solution is found. Else, restart the backwater curve calculation with (Q+Q*)/2 until convergence.
• else the discharge was given at the sluice gate. From Q, ha and hdo the value of hup can be determined.