When a fire breaks out in a tunnel, smoke diffuses widely in the direction of the ventilation airflow. As a result, the evacuation environment may not be sufficiently safe during a fire incident. When ventilation equipment in a tunnel is changed, the safety and economic efficiency of the new ventilation equipment must be evaluated in advance. However, it is dangerous and not financially feasible to undertake the verification of new ventilation equipment by performing a demonstration experiment owing to its cost and versatility. It is therefore useful for predicting an evacuation situation in which a fire breaks out in a tunnel by performing a numerical simulation and examining the evacuation safety of the tunnel. In this study, a tunnel fire was reproduced using the Fire Dynamics Simulator (FDS) fire simulation software. Moreover, an evacuation was simulated using the real-coded cellular automaton (RCA) method and the effects of the wind velocity and the number of evacuees in the tunnel on the evacuation time were examined.

In this study, closure relations for total and turbulent convection fluxes of flame surface density and scalar dissipation rate were developed (i) by placing the focus of consideration on the flow velocity conditioned to the instantaneous flame within the mean flame brush and (ii) by considering the limiting behavior of this velocity at the leading and trailing edges of the flame brush. The model was tested against direct numerical simulation (DNS) data obtained from three statistically stationary, one-dimensional, planar, premixed turbulent flames associated with the flamelet regime of turbulent burning. While turbulent fluxes of flame surface density and scalar dissipation rate, obtained in the DNSs, showed the countergradient behavior, the model predicted the total fluxes reasonably well without using any tuning parameter. The model predictions were also compared with results computed using an alternative closure relation for the flame-conditioned velocity.

A fire in an enclosed space, such as a room in a building, is generally called a compartment fire. To prevent the compartment fire, a sprinkler for first-aid fire-fighting is installed in rooms. However, it is difficult to determine the degree to which smoke generation and the fire spreading will be inhibited when sprinklers are on. In particular, demonstrating evacuation behavior assuming an actual fire is impossible. In this study, we evaluated an effectiveness of the sprinkler by numerical simulations. To consider evacuation dynamics, a real-coded cellular automata (RCA) was used, where we can freely set the direction and velocity of an evacuee based on a floor field model. To consider the situation in the room fire, we used a simulator called Fire Dynamics Simulator (FDS). Two cases with and without the sprinkler were compared to see the validity of the sprinkler on evacuation dynamics. The effect of smoke and the expansion of the fire-spreading region were discussed. Results show that, since the fire-spreading region disappears when the sprinkler is actuated, the evacuation time decreases. Even though the sprinkler is actuated, the smoke generated at the beginning of a fire diffuses inside the whole room. However, the duration of evacuees being overwhelmed by smoke is less, because the amount of smoke generated by the pyrolysis reaction is much decreased.

An analysis of local flame area was performed using DNS (Direct Numerical Simulation) databases of turbulent premixed flames with different density ratios and with different Lewis numbers. Firstly, a local flame surface at a prescribed progress variable was identified as a local three-dimensional polygon. And then the polygon was divided into some triangles and local flame area was evaluated. The turbulent burning velocity was evaluated using the ratio of the area of turbulent flame to that of planar flame and compared with the turbulent burning velocity obtained by the reaction rate.