One of the key technical problems of flood discharge tunnel with spiral flow shaft is gas burst being prone to occur at the outlet,as the discharging tunnel is difficult exhaust under the condition of high tail water level.For this regard,numerical simulation was conducted and combined with a tunnel project to study a novel type of vortex shaft in a flood discharge tunnel with submerged outlet.Flow pattern features,pressure distribution and other characteristics of this flow were obtained and they agreed well with the experimental results.The conversion mechanism of strong aerated turbulent flow to pressure flow and its influence on structure were discussed. Research showed that,the horizontal section can be divided into a mixing and energy dissipation area which is the main disinfection energy,an air bubble escaping area,an air discharge zone,and a smooth flow zone. In the condition of submerged outlet,the air escapes successfully, the flow pattern converts smoothly along the tunnel, and the bottom pressure is distributed reasonably. This research can be a reference for similar projects.
