Perforated Partition Walls in Extra-Long Tunnels: A One-Dimensional Flow Model Based on Orifice Theory

Perforated partition walls are widely employed in complex underground transportation systems to mitigate tunnel pressure waves, harness train-induced piston wind for reduced ventilation energy consumption, and support emergency operations. Building on orifice flow theory, this study develops a one-dimensional flow model for tunnels equipped with perforated partition walls. The model is applied to examine the aerodynamic performance of such walls in extra-long tunnels through a comprehensive parametric analysis, considering the presence of openings, opening ratio, spacing, and spatial arrangement. The results demonstrate that, for opening ratios, defined as the ratio of the perimeter of a single opening to the wetted perimeter of the tunnel on the train-passing side, ranging from 0 to 0.32, the model accurately captures train-induced pressure fluctuations. The introduction of a perforated partition wall reduces the overall amplitude of pressure fluctuations by 41.7% compared with the non-perforated configuration. Specifically, pressure peaks outside the leading and trailing cars decrease by 41.4% and 28.5%, respectively. Increasing the opening area enhances cross-wall airflow and effectively attenuates pressure fluctuations on the train-passing side, while reducing opening spacing further intensifies this effect. For a fixed number and ratio of openings, a uniformly distributed arrangement along the entire wall produces smoother pressure variations than configurations concentrated near the center or ends. An optimal design is identified, consisting of a uniform opening distribution with an opening ratio of 0.20 and a spacing of 10 m.