Fast Running Pool Fire Computer Code for Risk Assessment Calculations

Abstract

The Isis-3D computational fluid dynamics/radiation heat transfer computer code was developed to simulate heat transfer from large fires to engulfed packages for transportation risk studies. These studies require accurate estimates of the total heat transfer to an object and the general characteris tics of the object temperature distribution for a variety of fire environments. Since risk studies require multiple simulations, analysis tools must be rapid as well as accurate. In order to meet these needs Isis-3d employs reaction rate and radiation heat transfer models that allow it to accurately model large-fire heat transfer even when relatively coarse computational grids are employed. In the current work, parameters for the reaction rate model were selected based on comparison with soot volume fraction and temperature measurements acquired in a recent 6 m square pool fire under light wind conditions. The soot volume fraction Isis-3D uses to define the edge of the optically thick fire was determined using temperature measurements of a pipe engulfed 20-m-diameter pool fire with a steady 9.5 m/s crosswind. Accelerated simulations, in which the specific heat of the engulfed pipe was reduced by a factor of twelve below the measured values, reproduce the temperature data in the 11-minute crosswind fire using only 3.5 hours on a standard desktop workstation.