In practical applications, flammable materials are often arranged in arrays of discrete objects whose combustion properties may vary compared to that of a homogeneous material. In this study, the influence of spacing between arrays of wooden dowels on the rate of upward flame spread through arrays has been studied. This configuration adds to previous work on single columns of matchsticks (Gollner et al., 2012), in some ways modeling physics that appears in flame spread through wildland fuels and suspended cable trays. A single dowel was ignited at the base of an array of birch dowels with fixed spacings of 0.75, 1.0 and 1.5 cm and allowed to spread upwards. In the wider-spaced cases (1.0 and 1.5 cm), the flame spread upward mostly along the center column, igniting few dowels to its side. In the 0.5 cm spacing, however, flame spread exhibited a two-dimensional nature, spreading throughout the array in a V-shaped pattern. Comparing results to an existing theory for upward flame spread and burning of single vertical columns of matchsticks, the far-spaced arrays follow the previous theory (Gollner et al., 2012); however rates of upward spread are decreased through the closer-spaced arrays. This may be due both to impedance of the flow through the array, but perhaps more importantly to a lack of available oxygen for burning. In the denser spacing of this configuration, significant unburnt fuel vapors are seen released above the array of this configuration. Results for mass-loss rates and spread horizontally through the array are also presented.
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