Design of Trapezoidal Expansive Transitions

Open‐channel expansions for subcritical flows are encountered in the design of hydraulic structures such as aqueducts, superpassages, and so on. In these structures the flow tends to separate while subjected to the positive pressure gradient associated with flow deceleration, thus resulting in a considerable loss of energy. Considerable savings could be achieved if the transition is designed by minimizing the head loss incurred in it. In this paper which applies the optimal‐control theory, a methodology for the design of an expansive transition between a rectangular flume and a trapezoidal channel for a subcritical flow was evolved. Analyzing a large number of designed optimal transitions, empirical equations for the bed‐width and side‐slope profiles were obtained.