Scour of Clear Water Rock W-Weirs in Straight Rivers

Abstract

Scour characteristics downstream of rock W-weir structures were studied in a horizontal straight channel and under clear water conditions. For each structure, different hydraulic conditions were considered, including densimetric Froude numbers, water drops, and tailwaters. Results showed that the tailwater depth plays an important role in predicting the scour parameters. Dimensional analysis was used to derive equations to predict the maximum scour depth and length and the maximum dune height and length. Selected tests were conducted with an open W-weir. In this case, results show that the maximum scour depth decreases and its location shifts downstream with respect to classical W-weirs. Three types of scour morphology were classified: Type A, characterized by one scour hole and two ridges; Type B, with two scour holes and two ridges; and Type C, characterized by only one scour hole and one ridge.