Train-induced airflow effect on coupled heat and mass transfer in a permafrost tunnel

When a high-speed train passes through a tunnel, it disturbs the original airflow state in the tunnel, which is an aerodynamic and thermodynamic process. This process involves complex heat and mass transfer in the coupled fluid-solid system. To date, more attention has focused on train-induced aerodynamic forces, waves and acoustics in tunnels, and energy transfer has received limited attention. Needless to say, few studies have the train-induced airflow effect on coupled heat and mass transfer in permafrost tunnels. To solve this problem, we built a nu-merical model for the Fenghuoshan tunnel in permafrost regions based on three conservation principles and then simulated the aerodynamic and thermodynamic responses to a high-speed train. When the train enters the tunnel, a large mass of air is pressed from outside to the inside of the tunnel, and the air in front of the train is pushed and speeded up. A high-pressure zone appears in front of the train, while a low-pressure zone forms behind the train tail. Under the action of a pressure gradient, the air rapidly flows toward the low-pressure zone. In addition, the moving train disturbs the original airflow state in the tunnel. The train-induced airflow raises the air temperature in the permafrost, and the maximum rising temperature of the air can reach 1.6 ?. The heat energy in the air gradually transfers into the surrounding permafrost, causing the permafrost to thaw and reducing the tunnel's safety. Therefore, the train-induced airflow effect on the heat and mass transfers in permafrost deserves our attention and further study.