Influence of tunnel width on longitudinal smoke control

The objective is to carry out experiments on scale models and CFD calculations in order to study the influence of tunnel width W on critical velocity (for a given tunnel height H). By definition, the critical velocity is the minimum longitudinal velocity needed to prevent smoke back flow when a fire occurs in a tunnel. Two different experimental reduced scale models are used: the first one is a thermal model using a propane gas flame to simulate the fire and the second one is a densimetrical model in which the fire-induced- smoke is represented by a continuous release of an isothermal buoyant mixing. In both approaches, for aspect ratios W/H greater than unity, it is noticed that the critical velocity decreases when the width increases, as predicted by theory, but for low values of the aspect ratio (i.e. when W