Numerical simulation of air–water flow in gated tunnels

Abstract

Gated tunnels are among the important hydraulic structures which fulfil various functions. However, due to the high-velocity flow through these structures, critical flow conditions may occur. Generally, physical model studies are performed to optimise the design of these structures which are time consuming and also very expensive. In the present research work a three-dimensional numerical model was used to simulate complicated free-surface air–water flow in gated tunnels. The volume of fluid scheme was used together with the K–ε turbulence model in this simulation. The flow rating curve and air demand downstream of the service gate were computed at different gate openings and were compared with experimental data with good agreement. In addition a comparison of the calculated pressure distribution and cavitation index in the gate chamber with physical measurements showed the accuracy of the computational fluid dynamics model. Furthermore, a comparison of flow pattern and rooster tail formation downstream of the gate with experimental observations showed the capability of the numerical model in simulating the complex air–water flow in high-speed gated tunnels. This study shows the application of numerical simulation as a powerful tool in the design of hydraulic structures.