longitudinal ventilation

Longitudinal ventilation is a common technique for smoke management during a fire accident within tunnels. In this paper, fire and smoke movement behaviour in longitudinally ventilated tunnels is investigated focusing on critical ventilation velocity. Firstly, critical velocity (VC) is evaluated for different heat release rates and results are compared and verified with model scale experimental data. Secondly, two fire scenarios inside tunnels with different cross sections are arranged and the reliability of some existing correlations for VC is explored.

Emergency smoke ventilation for a uni-directional traffic road tunnel is studied using a CFD modelling approach. Fire scenarios in an uphill ramp for congested traffic conditions have been considered. Based on a longitudinal smoke ventilation system with a damper smoke-extraction device on the ceiling soffit, the impact of longitudinal ventilation (LV) control, operation of fire suppression intervention and emergency response delay have been quantitatively investigated.

Longitudinal ventilation systems are commonly installed in new tunnels in big cities of the Far Eastincluding Mainland China, Hong Kong and Taiwan. Many tunnels are found and some of them areinclined at an angle to the horizontal. However, smoke movement in those tilted tunnels is not fullyunderstood. Some longitudinal ventilation was designed based on presumed smoke movementpattern without experimental demonstration.Smoke movement pattern in a tilted tunnel model was studied by scale modeling technique.