Numerical Simulation of the Impact of Rainfall on Tunnel Fire

An improved understanding of tunnel fire dynamics is crucial for fire and life safety. This work underscores the significance of Computational Fluid Dynamics (CFD) techniques in addressing the interaction between tunnel fires and rainfall. Discrete phase model based on the Lagrangian approach is applied to simulate raindrops, and turbulence models of RANS (Reynolds Averaged Navier-Stokes) and LES (Large Eddy Simulation) are applied to simulate the fire field. This numerical work reveals the detailed fluid flow, temperature fields, and turbulence characteristics of tunnel fires under the impact of rainfall in portal. Results showed that the RANS model can predict the flow field better near the wall, while the LES model captures the small eddies in fire behaviors. Comparison between simulation and model-scale tunnel experimental data suggests that the LES model has a better prediction of temperature distribution for tunnel fires under no rainfall condition, while the RANS model performs better in predicting temperature distribution for tunnel fires under the effect of rainfall. Finally, this work simulates the full-scale tunnel fire under the impact of rainfall and demonstrates the CFD simulation of tunnel fire under extreme weather. Correlations between the local increased pressure and maximum airflow velocity and rainfall parameters are developed.