Optimal channel contraction for supercritical flows

The optimal transition for channel contraction with supercritical flows in a horizontal straight-wall channel is investigated. A new optimal contraction diagram is developed based on the fundamental relationship for oblique shock waves. The diagram may replace the commonly used trial-and-error procedures for the determination of the optimal contraction. Two equations are also proposed to approximate the functional relationship in the optimal contraction diagram. Two application tests are presented to demonstrate that the optimal contraction determined from the newly developed diagram agrees with those calculated by the trial-and-error method. Numerical simulations are also used to examine the validity of the new optimal contraction diagram. © 2004 International Association of Hydraulic Engineering and Research.