Parallel burning of thin cellulose sheets using fire dynamics simulator

Direct numerical simulations (DNS) of upward flame spread over multiple thin cellulose sheets are carried out in Fire Dynamics Simulator (FDS). The cell sizes are varied from 0.16 mm near the fuel sheets to the order of 1 mm near the outer boundaries. The parameters varied are the number of sheets (n = 1, 2 and 3) and the separation distances (s = 5 mm, 10 mm, 15 mm and 30 mm). Time-averaged spread rates are validated against the experimental results available in the literature. As the flame spreads, the temperature, velocity and oxygen fields are analyzed systematically. Variations of heat flux to the fuel sheets are estimated. The maximum flame spread rate is obtained for the case of n = 3 and s = 15 mm. It is found that among all the cases, the net surface heat flux for this case is the maximum. At a separation distance of 30 mm, the average flame spread rate approaches the corresponding value for the case of single sheet indicating that the interference effect of the neighboring flame has diminished almost entirely.