An experimental study on the influence of local loss on ventilation characteristic of dividing flow in urban traffic link tunnel

In order to deeply study the local ventilation loss coefficient of the bifurcation structure in urban traffic link tunnel, a scale 1:50 model with bifurcation structure was designed and constructed based on the Xiamen Haicang undersea tunnel. The ventilation characteristics and local ventilation loss coefficient are studied for the bifurcation structure through a model experiment. The results show that the length-to-height ratio at the bifurcation structure has a significant influence on the local loss coefficient. When the split ratio is greater than 0.5, the local loss coefficient of direct flow will decrease with the increase of this ratio, however it will increase when the split ratio is less than 0.5. The local loss coefficient of split flow will just decrease with the increase of the length-toheight ratio. The local loss coefficient of direct flow and split flow will decrease during the process of increasing the bifurcation angle from 10 degrees to 20 degrees. When the bifurcation angle is increased from 160 degrees to 170 degrees, the local loss coefficient of direct flow is independent of the bifurcation angle. The results clarify the influence law of the bifurcation structure on the local loss coefficient and provide the reference for the ventilation design in urban traffic link tunnel.