Use of the Kit Fox field data to analyze dense gas dispersion modeling issues

The 1995 Kit Fox dense gas field data set consists of 52 trials where short -duration CO2 gas releases were made at ground level over a rough surface d uring neutral to stable conditions. The experiments were intended to demons trate the effects on dense gas clouds of relatively large roughnesses typic al of industrial process plants. Fast response concentration observations w ere made by 80 samplers located on four downwind lines (25, 50, 100, and 22 5m), including profile observations on three towers on each of the closest three arcs. Detailed meteorological measurements were made on several tower s within and outside of the roughness arrays. The data analysis emphasized the variation of maximum concentration with surface roughness, the dependen ce of cloud advection speed on cloud depth, the variation of the three comp onents of dispersion with ambient turbulence, and the dependence of vertica l entrainment rate on ambient friction velocity and cloud Richardson number . The Kit Fox data were used to evaluate a specific dense gas dispersion mo del (HEGADAS 3 +), with emphasis on whether it would be able to account for the increased roughness. The model was able to satisfactorily simulate the observed concentrations, with a mean bias of about 5% and with about 90% o f the predictions within a factor of two of the observations. (C) 2001 Else vier Science Ltd. All rights reserved.