Abstract
This report presents water surface profiles and their lengths from brink to critical depths in rectangular smooth channels. As a non-dimensional expression, a similar water surface profile can be obtained under various types of channel slopes (horizontal to critical slopes). Also, the experimental investigation yields that the relative length from brink to critical sections depends on channel slope and Reynolds number. Appling the momentum equation to the control volume from brink to critical sections supported the experimental evidence on the similar water surface profile and the change of relative length with channel slope and Reynolds number. Further, the comparison of the water surface profile on the trapezoidal weir has been shown. The similar water surface profile could be obtained as in the case of recatangular channels. For the length from brink to critical sections, the relative length depends on the relative drop height under a given Reynolds number.
