Urban tunnels are generally narrow and fire smoke can hardly diffuse.In the present study,numerical simulation is used to analyze the diffusion of high temperature smoke produced by fire inside a specific tunnel(the K...Urban tunnels are generally narrow and fire smoke can hardly diffuse.In the present study,numerical simulation is used to analyze the diffusion of high temperature smoke produced by fire inside a specific tunnel(the Kaiyuan tunnel).The results are compared with similar data relating to other tests to determine the validity of the numerical method.Moreover,the critical velocity obtained by numerical simulation of 5 MW,20 MW,and 50 MW fires in curved and linear sections of the considered tunnel is compared with the values obtained using empirical formulas.The results show that,for the tunnel ventilation design,it is necessary to consider the fan pressurization at different sections and the fan pressurization should be higher at curved sections than that at linear sections.The safety of personnel escaping under different critical velocity values in the linear section has also been considered.On the basis of our findings,if only relying on natural ventilation,people can escape safely for the case of small fires,whereas for medium and large fires,it is necessary to turn on mechanical ventilation in time(and in order to avoid the danger caused by rapid diffusion of smoke,the timing of mechanical ventilation should be carefully tuned).展开更多
In the present study,the laws of smoke diffusion during forest fires are determined using the general principles of fluid mechanics and dedicated data obtained experimentally using an“ad hoc”imaging technology.Exper...In the present study,the laws of smoke diffusion during forest fires are determined using the general principles of fluid mechanics and dedicated data obtained experimentally using an“ad hoc”imaging technology.Experimental images mimicking smoke in a real scenario are used to extract some“statistics”.These in turn are used to obtain the“divergence”of the flow(this fluid-dynamic parameter describing the amount of air that converges to a certain place from the surroundings or vice versa).The results show that the divergence of the smoke depends on the outside airflow and finally tends to zero as time passes.Most remarkably,compared with clouds and fog,smoke has a unique dynamic time-evolution curve.The present study demonstrates that as long as image processing technology and intelligent monitoring technology are used to monitor the gas flow in a forest,the occurrence of forest fires can be quickly diagnosed.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11372166).
文摘Urban tunnels are generally narrow and fire smoke can hardly diffuse.In the present study,numerical simulation is used to analyze the diffusion of high temperature smoke produced by fire inside a specific tunnel(the Kaiyuan tunnel).The results are compared with similar data relating to other tests to determine the validity of the numerical method.Moreover,the critical velocity obtained by numerical simulation of 5 MW,20 MW,and 50 MW fires in curved and linear sections of the considered tunnel is compared with the values obtained using empirical formulas.The results show that,for the tunnel ventilation design,it is necessary to consider the fan pressurization at different sections and the fan pressurization should be higher at curved sections than that at linear sections.The safety of personnel escaping under different critical velocity values in the linear section has also been considered.On the basis of our findings,if only relying on natural ventilation,people can escape safely for the case of small fires,whereas for medium and large fires,it is necessary to turn on mechanical ventilation in time(and in order to avoid the danger caused by rapid diffusion of smoke,the timing of mechanical ventilation should be carefully tuned).
基金This work was supported by Civil Engineering Specialty of Brand Construction Point of Private Colleges and Universities in Henan Province(No.ZLG201702).
文摘In the present study,the laws of smoke diffusion during forest fires are determined using the general principles of fluid mechanics and dedicated data obtained experimentally using an“ad hoc”imaging technology.Experimental images mimicking smoke in a real scenario are used to extract some“statistics”.These in turn are used to obtain the“divergence”of the flow(this fluid-dynamic parameter describing the amount of air that converges to a certain place from the surroundings or vice versa).The results show that the divergence of the smoke depends on the outside airflow and finally tends to zero as time passes.Most remarkably,compared with clouds and fog,smoke has a unique dynamic time-evolution curve.The present study demonstrates that as long as image processing technology and intelligent monitoring technology are used to monitor the gas flow in a forest,the occurrence of forest fires can be quickly diagnosed.