Unconfined Expansion of Supercritical Water Flow

Abstract

The spread of supercritical free-surface flow on a smooth horizontal plane is considered. Experiments with selected approach Froude numbers are presented indicating that the effect of the Froude number may be dropped for hypercritical flow, that is, for values larger than 3. Also, a simple relation between local streamline direction and local flow depth is established. For sufficiently large approach flow depth, the Froude similarity law governs the phenomenon. Assuming that the streamwise velocity component is constant yields a system of equations identical to the one-dimensional simple wave problem. The solutions are compared with observations, and reasonable agreement is noted. Further particularities of hypercritical channel flow are established that are important for the numerical simulation of such currents. The features of expansion flow are documented with selected photographs. Supercritical unconfined expansion flow on a horizontal plane is studied. The governing equations can be shown to simplify considerably for hypercritical flow. A complete description is given based on both computations and experiments.