Modeling instantaneous heavy gas releases with FDS5

•Instantaneous release of a heavy gas has been modeled with FDS5.•Features of LES modeling had been discussed in view of the character of the gravity current flows.•Comparison with experimental data from literature validate the present approach for the present testcase.•FDS5 could be used for modeling heavy gas releases under calm environment conditions, when dispersion is gravitationally driven.

Releases of heavy flammable gases are responsible of many major civil and industrial incidents with very large property loss and number of victims. Fire Dynamics Simulator 5 (FDS5) is a fire modeling CFD code developed by NIST that is widely known in the fire engineering community.The code is specifically suited to deal with multicomponent buoyancy driven natural flow, where the low Mach number assumption holds and the pressure is only slightly different from the background atmospheric value. This study presents the comparison between experimental results relevant to heavy gas or vapors instantaneous releases and FDS5 predictions. Comparison with experimental results shows that concentrations and cloud arrival times in the heavy gas cloud regime, when concentrations of the heavy component in the plume are high, can be predicted by the code. The present work is focused on gravitationally driven heavy gas dispersion in calm environments.