Author(s): Youichi Yasuda
Linked Author(s): Youichi Yasuda
Keywords: Hydraulic jump Low Drop Structure Assembled Boulders Seepage flow Local Scour Protection
Abstract: Generally, a hydraulic jump is formed at the downstream of a low head drop structure. According to hydraulic design manuals, protective blocks are installed downstream of the drop structure to prevent local scouring. If the streamline at the beginning of the jump is curved, a mainstream of the jump is located near the bottom, and the position of the main stream is continued far downstream. During flood stages, jump formation causes the mainstream in the jump to be located near the bottom, forming local scouring downstream of the drop structures. The protection blocks have no function to control the main flow, and the main flow during the jump does not rise to the water surface, and the mainstream near the bottom continues downstream of the protection blocks. There is no technique in hydraulic investigations to substantially protect the riverbed at the downstream of the low drop structure. Recently, the installation of consecutively assembled boulders on the ramp may reduce the velocity of flow near the bottom and allow the mainstream to rise to the surface, deflecting it from the side bank to the center of the river. The authors proposed the installation of consecutively assembled boulders in the jump formation region downstream of a low drop structure. Flow velocity measurements showed that the mainstream of the jumps rose toward the water surface and deflected from both sidewalls to the center. The mean flow velocity and standard deviation reduced near the bottom downstream of the area where the assembled boulders were installed. The seepage flow in the assembled boulders may help the reduction of the velocity near the bottom.
Year: 2025