Fire Safety Science Digital Archive

Numerical study is performed to investigate an intermediate scale, turbulent fires in a horizontal model tunnel exposed to air flow ranging from 0.5 to 2.5 m/s. Controlling mechanisms of three dimensional flow, combustion, soot production and radiation are coupled with a Large Eddy Simulation. The computed, time-averaged flame length and height are compared with experimental data, and a relatively good agreement is attained. It is found that the persistent flame length is approximately 3-4 times the pyrolysis length, and however, the intermittent flame length is up to 6 times the pyrolysis one. The minimum air velocity of 1 m/s is predicted to suppress the hotter backlayering flow upstream of the fire section in a tunnel. As the air velocity decreases, radiation increasingly becomes the dominant mode of heat transfer from the flame to the wall surface.