Numerical Studies on the Heat Insulation and Smoke Control Effect of Water Mist Screen Under Longitudinal Ventilation in Bifurcated Tunnel

As the complex structure, the situation of fire accident of a bifurcated tunnel will be more severe than that of a long-straight tunnel. It is of practical significance to research the control effect of the water mist screens in the bifurcated tunnel fire. In this paper, a 1/10 scale bifurcated tunnel model is established based on FDS to study the heat insulation and smoke control effect of water mist screen under the action of longitudinal ventilation when a fire occurs at the fork. The results indicated that: The coupling of longitudinal ventilation and water mist has the most significant inhibition effect on ceiling temperature and ceiling CO concentration in the upstream area of main tunnel, the larger wind speed results in better heat insulation and smoke control effect in the upstream area of main tunnel. Overall, the more the number of water mist nozzle rows or the smaller the particle size, the better the control effect on the ceiling temperature and ceiling CO concentration of the main and branch tunnel. In addition, compared with the main road, the water mist screen section of branch tunnel has the limited ability to block the smoke diffusion.