Flow characteristics of an air chamber in a rail tunnel

In this paper, the flow characteristics of an air chamber inside a tunnel when subjected to train-nose-entry wavefronts were analyzed using numerical simulation. The results demonstrate that there exists a specific range of connection sizes for a fixed volume of air chamber, which imparts an under-damped characteristic to the chamber. Additionally, the pressure distribution within the air chamber and tunnel exhibits a noticeable three-dimensional effect as a consequence of the non-uniform flow field at the connection of the air chamber. The difference in the numerical results of the maximum pressure gradient is primarily observed at the air chamber connection when comparing the axisymmetric model to the one-dimensional model. However, this difference gradually diminishes to approximately 1% after the wavefronts have traversed through the air chamber for a distance of approximately 5 m. Furthermore, a scaled experimental setup was constructed to compare the obtained numerical results with the experimental data, successfully validating the accuracy of the numerical method.