Study of flow characteristics in tunnels induced by canyon wind

Mountain tunnel is inevitably connected to those canyon areas that could result in a very special situation for the related designs. When the airflow goes through the canyon from an open terrain, it is accelerated to a strong canyon wind under the Venturi effect. However, the flow characteristics in tunnels affected by the canyon wind are still not known. Therefore, the flow characteristics in the tunnel, such as structure, velocity and pressure distributions, together with external canyon wind, were investigated, for the first time, through this study. Different canyon wind velocities and tunnel types were analyzed numerically and experimentally. The results showed that the flow structure in tunnels can be divided into the vortex region and the uniflow region. Besides, a linear relationship was found between the average cross-section velocity of uniflow regions and the canyon wind velocity, where a quadratic relationship was also found between the minimum pressure of vortex regions and the canyon wind velocity. Furthermore, the results indicated that the flow characteristics in the tunnel induced by canyon wind are mainly affected by the hydraulic diameter of the tunnel, where the influences of different types of cross-sections with the same hydraulic diameter are limited.