Author(s): Rahil Ahmad; Hariom Gautam
Linked Author(s):
Keywords: CFD Tunnel Spillway Discharging Capacity Velocity Distribution
Abstract: A tunnel spillway is a hydraulic structure designed to safely convey excess water from a reservoir through a tunnel. This study conducts a hydraulic assessment using CFD-based numerical modelling to evaluate the conversion of existing diversion tunnels into tunnel spillways, thereby enhancing discharging capacity of the dam. The tunnels, designated as Tunnel Spillway-1 (TS-1) and Tunnel Spillway-2 (TS-2), were modeled at a 1:40 scale using ANSYS ICEM and simulated in ANSYS Fluent. A detailed three-dimensional tetrahedral mesh, comprising approximately 3.9 million elements, was generated following a mesh sensitivity analysis to ensure accuracy. The simulations utilized the SST k-ω turbulence model, with pressure boundary conditions applied at the inlet and outlet to replicate reservoir and downstream river conditions. Discharging capacity of the tunnel spillways were computed using CFD for different reservoir water levels and tail water level. Velocity distributions at key locations along the tunnel spillways were plotted and analyzed. The findings indicated that, at maximum reservoir levels, TS-1 and TS-2 could pass flows of 1834.02 m3/s and 1843.93 m3/s, respectively, and discharge decreases as tailwater levels increased. This study demonstrates that the 3D numerical model is an accurate, cost-effective, and efficient method for simulation of flow in the tunnel spillways.
Year: 2025