3D numerical model analysis of the ski-jump spillway downstream of the Wushe Sediment Bypass Tunnel

The Wushe Dam, located in Ren'ai Township, Nantou County, Taiwan, has experienced a significant reduction in storage capacity due to sedimentation since it began operation in 1959. To address this issue, a sediment bypass tunnel was planned, comprising various hydraulic structures such as an intake, gate, air vent, tunnel, spillway, and energy dissipation. This paper focuses on the hydraulic analysis of the ski-jump spillway and plunge pool energy dissipation. A three-dimensional (3D) numerical simulation was conducted using Flow-3D, computational fluid dynamics (CFD) software, to simulate complex flow dynamics and energy dissipation mechanisms. The study aims to predict the trajectory of the water jet and the required size of the energy dissipation pool under varying discharges. Results indicate that the integrated design effectively reduces high-velocity flows, preventing shock waves and minimizing potential scour damage to the riverbed. Furthermore, the installation of a weir at the downstream river manages the water level and enhances the cushioning effect, ensuring stable and safe sediment bypass tunnel operations.