Study on effects of the train-induced airflow on the temperature field of high-speed railway tunnels in cold regions

High-speed railway tunnels in cold regions often suffer severe frost damage in winter. In these tunnels, the traininduced airflow is generally regarded as an important factor exacerbating frost damage. Thus, the CFD methods were used in this paper to investigate the effects of the train-induced airflow on the temperature field of tunnels in cold regions. In this simulation, the behavior of the train passing through the tunnel was simulated using a dynamic mesh technique. The results show that the effects of the train-induced airflow will last for about 16 min when one train passes through the tunnel at 350 km/h. High-speed trains carry large amounts of lowtemperature air into the tunnel, resulting in lower tunnel air temperatures and enhancing convective heat transfer between the air and the structure. The effects of the train-induced airflow are proportional to the train's speed. The minimum air temperature of the monitored cross-section at 350 km/h is 12.6% lower than that at 250 km/h. The effects of the train-induced airflow are negatively correlated with the interval between two trains passing through the tunnel. For every 5 min of interval time reduction, the local lowest air temperature drops by 0.55 degrees C and the heat dissipation rate of the structure increases by 12.3%. The lower the ambient temperature, the more significant the temperature drop caused by the train-induced airflow. However, the train-induced airflow can be a beneficial factor during the high temperature hours of the day.