A new plug arrangement,which was a combination of vertical gradually contracted plug and venturi plug as well as horizontal gradually contracted plug,was proposed for meeting the requirement of energy dissipation of plug discharge tunnel.The plug discharge tunnel with high head,large flow rate and low tailwater lever was reconstructed from a diversion tunnel.Then the RNG k-εtwo-equation model for turbulent flow and the VOF method were applied to simulate the turbulent flow in the plug discharge tunnel. The distribution of some important hydraulic characteristics was obtained, such as pressure, velocity, and energy dissipation rate. Moreover, parts of the calculations were compared with the experiments．It was concluded that the strong turbulence, strong shear jet and large-scale vortex flow in the pressure plug discharge tunnel could be simulated. And the new plug arrangement remarkably enhanced the efficiency of energy dissipation due to the strong turbulence taking place in the plug discharge tunnel.
