Supercritical Flow behind Chute Piers

The present paper provides an experimental study of standing waves generated by piers in chute spillways. The wave pattern is described with the coordinates at the wave beginning, at the section of maximum wave height, and at the wave end. Wave 1 refers to the immediate tailwater zone of the pier, whereas wave 2 may appear at the chute wall farther downstream. Both waves tend to become independent of the approach Froude number provided $F_0>5$. Wave 1 is shown to depend exclusively on the ratio of approach flow depth to pier width, whereas wave 2 is also affected by the relative wall distance. The flow is described both analytically and by selected photographs. Means to reduce the wall waves are presented. The principle of wave reduction involves a shift of wave phases of the flows originating from either pier side. The optimum length of pier extension length is discussed and a design procedure is represented. As a result, standing chute pier waves can practically be inhibited.