Supercritical Flow in Channel Junctions

Abstract

Using both a theoretical and an experimental approach, the main flow features in junctions with thoroughly supercritical flows are considered. The junctions are characterized by rectangular channels of equal branch width and sharpedged corners. Junction angles of 22.5° and 45° are considered. Expressions are given for the direction of the main wave front, and the wave angles in both the upstream, and the lateral branches. The prediction is based on a conventional crosswave analysis, in which streamline curvature effects were not incorporated. Yet, reasonable agreement is found between predictions and observations regarding the maximum wave height, and its position in the junction. Furthermore, the velocity field, and the flow surface are discussed for typical flow configurations. Finally, the limits of thoroughly supercritical flow conditions are verified by the momentum equation, thereby including the flow contraction generated at the inflow to the downstream branch. Conclusions are given from which a design may easily be accomplished.