A study on grid aspect ratio of fire dynamics simulator

Title & Authors
A study on grid aspect ratio of fire dynamics simulator
Kim, Won Ouk; Park, Woe-Chul;

Abstract
The FDS is one of the most used programs for fire analysis and needs an optimal grid selection for an accurate analysis. This study selected various grid aspect ratios (ARs) for selection of optimal grid and analyzed them with FDS v 6.1.2. A calculation time of 10 min. was used, which is enough to obtain the time average value of temperature changes. Temperature, visibility, and the time average value of mass balance are obtained from 200-600 s, which is a period of maintaining quasi-steady state. Two polyurethane fires of 1 [MW] and 2 [MW] in two enclosures of $\small{10{\times}10{\times}3[m^3]}$ and $\small{20{\times}20{\times}3[m^3]}$ were considered. Time variations of heat release rates, temperature, visibility, and mass balance were compared for ARs from 1-6. The heat release rates were accurate for all aspect ratios regardless of fire and enclosure sizes. The quasi-steady state temperature and visibility were well predicted for $\small{AR{\leq}5}$. Temperature drop and skewness of mass conservation, however, increased with increasing aspect ratio. Therefore, careful investigation of the grid size is recommended in performance-based design when $\small{AR{\geq}3}$, where temperature and visibility in early stage of a fire are important parameters. For accurate simulations of enclosure fires, grid sizes of 0.1~0.2 [m] and smaller in the vertical direction and $\small{AR{\leq}2}$ are recommended.
Keywords
Fire simulation;Grid size;Aspect ratio;Temperature;Visibility;Mass balance;
Language
Korean
Cited by
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