Investigation on the Tunnel Curvature Effect upon the Ceiling Temperature of Tunnel Fires: A Numerical Simulation

This paper investigates the temperature distribution in curved tunnels through numerical simulation method. Applying in the Large Eddy Simulation by Fire Dynamic Simulator, models of tunnel fire with different curvature radiuses and heat release rates are set up, and the temperature in the tunnel are acquired by setting a series of thermocouples at the tunnel ceiling. After the simulations, the results show that the temperature is slightly higher for concave wall than that of convex wall for the far away positions from the fire source, which is different from that in a straight tunnel. The smoke movement in the tunnel is explained by analyzing the smoke force and the flow field. Meanwhile, even the longitudinal temperature decay could be well proposed through exponential fittings, the decay coefficients are found to be different. The decay coefficient for each curvature radius condition is linearly increased with the increasing tunnel curvature, but less depended on the heat release rate of fire. Finally, a new exponential decay model is well proposed for the longitudinal temperature predictions for various tunnel curvature conditions.