開水路
h o = ( Q 2 C 2 B 2 I ) 1 3 {\displaystyle h_{o}=\left({\frac {Q^{2}}{C^{2}B^{2}I}}\right)^{\frac {1}{3}}}
h D ≃ 0.81 {\displaystyle {\frac {h}{D}}\simeq 0.81} のとき、 v v 0 = 1.14 {\displaystyle {\frac {v}{v_{0}}}=1.14}