Fire properties in near field of square fire source with longitudinal ventilation in tunnels

In order to understand fire phenomena in the near field of a fire source in a tunnel, experiments were conducted using three kinds of model tunnels of which the dimensions were 1/10 scale, 1/2 scale and full scale, having rectangular and horseshoe cross-sections. Square fire sources were employed as model fire sources. The aspect ratio of the tunnel cross-section, heat release rate and longitudinal forced ventilation velocity were varied. Empirical formulae for flame tilt, apparent flame height, maximum temperature of the smoke layer and its position were developed based on the results obtained in the 1/10 scale model tunnel. The effect of aspect ratio of tunnel cross-section was incorporated in these models. It was found that the length defined by H-3/2/b(1/2) became a representative length for investigating fire phenomena in tunnels. It is also confirmed that these empirical formulae are sufficiently applicable for predicting fire phenomena in the near field of square fire source from the comparison with the results in 1/2 and full scale experiments. (C) 2003 Published by Elsevier Science Ltd.