Modeling longitudinal ventilation in tunnels using fire dynamics simulator

This paper discusses modeling tunnel fires using the computational fluid dynamics model Fire Dynamics Simulator (FDS). The model assumes that the speed of sound is infinite which leads to challenges related to solving the equation for pressure. The problem is particularly acute when multiple meshes are used to solve the governing equations in parallel. A method is presented in which the 3-D Poisson equation for the pressure, which is solved on each mesh, is approximated by a 1-D equation over the entire length of the tunnel. The 1-D solution serves as a preconditioner for the 3-D solver. This method is tested by comparing the model to three sets of experiments, one small-scale, one reduced-scale, and one full-scale. For each set of experiments, the intent is to predict the extent of the smoke back-layering. •Challenges related to modeling tunnel fires.•Comparison of simulation results to small-scale Wu and Bakar experiments/correlation.•Comparison of simulation results to full-scale Memorial Tunnel experiments.•Comparison of simulation results to recent experiments that include sprinklers.