Fire Safety Science Digital Archive

The critical angle for flame deflection in fires in inclined trenches was determined using the Computational Fluid Dynamics (CFD) code FLOW3D. The trenches had rectangular cross-sections and contained rectangular burners which extended the full width of the trench. Both two and three-dimensional simulations were carried out. The flowfield was simulated transiently and allowed to develop towards a final steady state. The critical angle was independent of the heat release rate. The three-dimensional simulations gave critical angles close to those measured in experiments. The critical angle was dependent on the geometry of both the trench and the burner. Longer, thinner burners and/or higher trench walls reduced the critical angle towards the value of 10 degrees determined for two-dimensional simulations. Square trenches with square burners had a critical angle of approximately 25 degrees. The critical angle was dependent on the trench and burner geometries through their effect on the shape of the plume within the trench.