Effects of longitudinal wind and sidewall restriction on downstream radiative heat flux and temperature rise distribution in tunnel fires

This paper presents an experimental study on downstream radiative heat flux and temperature rise distribution of tunnel fires under the combined effects of longitudinal wind and sidewall restriction. Two fire locations, i.e., centerline fire and sidewall fire, were considered, and the wind speeds were varied between 0 and 3 m/s. The results show that under smaller ventilation velocity, the downstream radiative heat flux of sidewall fire is larger than that of centerline fire. As the ventilation velocity increases, the radiative heat flux of two fire locations both firstly increase and then decrease with increasing distance. The position of the peak radiative heat flux depends on the evolution of the flame drag and moves away from the fire center with increasing wind speed and heat release rate (HRR). Based on the solid flame assumption, thermal radiation models are proposed and validated by experimental results. A similar spacial distribution trend was observed for temperature rise with varying fire locations and wind speeds. The distance from peak temperature rise to fire center is related to the flame drag front and increases with HRR and ventilation velocity. Finally, correlations for peak temperature rise, its locations and the temperature rise attenuation beyond the peak value were established.