numerical study on natural ventilation around a burning car inside a tunnel

This study aimed to analyse the flow and temperature fields around a car on fire inside a medium-size tunnelunder natural ventilation. the study used the fire dynamics simulator (fds), which is an open-source softwarepackage, to simulate the thermo-fluidic characteristics inside the tunnel. a constant heat release rate (hrr)was assumed to ensure the release of consistent heat from the car while varying the speed of the mass fluxnatural ventilation. a medium-size tunnel and scaled car were modelled to simulate a realistic fieldenvironment; the car was assumed to have its primary components, including the body frame, tyres, seats, andother flammable materials. the constant hrr was set at 3.8 mw , which was measured in a field experimentusing a cone calorimeter. the closed car windows were set to break when the temperature around them reached 600°c. additionally, natural ventilation was one of the parameters used in the calculation; it was assigned asan inlet condition, referred to as the steady longitudinal inlet velocity, and ranged from 1.8 to 3.0 m/s. basedon the ventilation velocities, the variations of the flow characteristics, temperature field, turbulence kineticenergy levels, and vortex structure inside the tunnel were investigated. additionally, the critical longitudinalvelocity for natural ventilation was estimated by performing the current simulation under different ventilation velocities. given that the thermo-fluidic parameters and geometry information are all similar, the fds results were compared to those from three semi-empirical models for predicting critical ventilation velocities from previous studies.