ABSTRACT
Now Q is a maximum when A*)P2 is a maximum. If x is some variable, such as a leading dimension, the condition for maximum discharge is (d/dx)(A5/P2) = 0. Thus
For a given sectional area A , dA/dx = 0, and hence the maximum dis charge is obtained when
or
(7.25)
(7.26)
that is to say when the wetted perimeter is a minimum. This section is known as the best hydraulic section. Furthermore, it follows that for a
given discharge the sectional area is a minimum, although the excava tion volume is not a minimum unless bank-full flow conditions pertain.