Research Of The Pressure Induced By Traffic Wind On The Wall Of Urban Tunnel

The main factors of the partition length of urban tunnel include that, the critical concentration of pollutants and critical wind speed, the emission concentration in portals and exhaust outlet. Therefore the ventilation shaft of multi-modular is adopted widely, but it's mechanical tower is so hard to adapt to city view, and it cost too much. The ventilation method of setting up natural openings on tunnel wall directly, have been developed in recent years, it could renew air in tunnel though the composite effect of traffic wind and nature wind with openings. The current design code don't involve the above ventilation method, so it's need to research it.The paper shall research the change and distribution law of the pressure on the wall of one-way tunnel in only effect of traffic wind with Fluent,that without openings. The research of pressure change law on tunnel wall indicate that, the pressure of all point on wall change periodic, and sometimes positive value, sometimes negative value. The wall in any condition, the time ratio of positive value is 0.2, and the time ratio of positive value is 0.8. The mean value of negative pressure is larger than positive pressure. The mean positive pressure and absolute mean negative pressure on side-wall is larger than that on top-wall. Pressure distribution is uniformity on top-wall in the same section. The pressure of traffic direction appears the law of wave-mode rising totally, peak value .and valley value is rising totally.Then the paper shall study the practical application of the research. It reveals that it's better to set up openings on side-wall than top-wall though integrated analysis. The same openings in different landscape orientation of the same section have the same ventilation condition. It's total value of inlet is larger than outlet of openings setting up uniformity along traffic direction. So for practical projects we should analysis the dilution effect of pollutant induced by in-let or out-let wind to confirm the natural openings could or not meet the ventilation demand and install mechanical equipment. When it's need to set up openings on limited area, the location of openings should be set up in somewhere near tunnel exit. The paper provide reference to relevant study and the design of urban tunnel ventilation system.