Effects of Step Transverse Slopes on Locations of Inception Point of Flow over Stepped Spillways
Abstract
In this experimental study, the effects of the steps having transverse slope in a zigzag pattern on the inception point location for flows over the stepped flat spillways were experimentally explored. Accordingly, three wooden stepped spillways were erected in a rectangular flume and tested under several discharges; ranging from 0.003 to 0.05 m3/s. The dimensions of the stepped spillways, each has thirty-two steps, were 0.605 m, 0.96 m, and 1.92 m for the width, depth, and length respectively. Thirty-two steps (with three different transverse slopes ranging from zero to 2.84˚) were cut into the surface of the models from the crest to the toe. From the results, it was found that the distances of the inception points from the downstream edge of the spillway crest were decreased by 37%, on average, for the stepped spillways with steps having a transverse slope of 2.84º. It was also found that the onset of the skimming flow for the stepped spillways with steps having the transverse slope occurred at higher discharges; yc/h ≥ 2.06. In addition, an expression for calculating the locations of the inception point for flows over stepped spillways, for longitudinal slope equals 26.6° and 1 < F* < 10, was obtained
