Abstract
The analysis of characteristics of turbulent flow and thermal boundary layer for natural convection caused by fire along vertical wall is performed. The 4m-high vertical copper plate is heated and kept at a uniform surface temperature of <TEX>$60^{\circ}C$</TEX> and the surrounding fluid (air) is kept at <TEX>$16.5^{\circ}C$</TEX>. The flow and temperature is solved by large eddy simulation(LES) of FDS code(Ver.6), in which the viscous-sublayer flow is calculated by Werner-Wengle wall function. The whole analyzed domain is assumed as turbulent region to apply wall function even through the laminar flow is transient to the turbulent flow between <TEX>$10^9$</TEX><<TEX>$Gr_z$</TEX><<TEX>$10^{10}$</TEX> in experiments. The various grids from <TEX>$7{\times}7{\times}128$</TEX> to <TEX>$18{\times}18{\times}128$</TEX> are applied to investigate the sensitivity of wall function to <TEX>$x^+$</TEX> value in LES simulation. The mean velocity and temperature profiles in the turbulent boundary layer are compared with experimental data by Tsuji & Nagano and the results from other LES simulation in which the viscous-sublayer flow is directly solved with many grids. The relationship between heat transfer rate(<TEX>$Nu_z$</TEX>) and <TEX>$Gr_zPr$</TEX> is investigated and calculated heat transfer rates are compared with theoretical equation and experimental data.
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