Study on the diffusion law of ventilation airflow in high altitude spiral tunnel

In order to explore the unique engineering design of spiral tunnel, its structural characteristics, complex terrain and changeable climatic conditions have a significant impact on the flow field in the tunnel, which makes it significantly different from the linear tunnel in terms of air flow diffusion. Through numerical simulation, factors such as fan supply speed, tunnel natural wind, altitude and longitudinal slope are adjusted. The law of airflow diffusion in high altitude spiral tunnel is studied. The results show that the instability of the flow field increases with the increase of the fan supply speed. The increase of altitude has little effect on the flow field distribution in the tunnel, but will reduce the fan pressure boost efficiency. At a small slope, the airflow is evenly distributed, and a concentrated high-speed area will be formed with the increase of the slope, but a large slope will lead to the dispersion of the airflow. It can be seen that through fitting analysis, the relationship formulas of tunnel entrance distance and static pressure at different altitudes and tunnel entrance distance and static pressure at different gradients are obtained. These formulas are helpful to understand the law of airflow diffusion.