UNCONFINED EXPANSION OF SUPERCRITICAL WATER-FLOW

The spread of supercritical free-surface flow on a smooth horizontal p lane is considered. Experiments with selected approach Froude numbers are presented indicating that the effect of the Froude number may be d ropped for hypercritical how, that is, for values larger than 3. Also, a simple relation between local streamline direction and local flow d epth is established. For sufficiently large approach flow depth, the F roude similarity law governs the phenomenon. Assuming that the streamw ise velocity component is constant yields a system of equations identi cal to the one-dimensional simple wave problem. The solutions are comp ared with observations, and reasonable agreement is noted. Further par ticularities of hypercritical channel flow are established that are im portant for the numerical simulation of such currents. The features of expansion flow are documented with selected photographs. Supercritica l unconfined expansion flow on a horizontal plane is studied. The gove rning equations can be shown to simplify considerably for hypercritica l flow. A complete description is given based on both computations and experiments.