The vulnerability of our society against major accidents or attacks has received significant attention in recent years. If the potential hazard can be defined, it may be possible to better prepare against the resulting consequences. Using FLACS, GexCon can help estimate the consequences of many potential major accident scenarios.

Massive releases of toxic industry chemicals, either from storage vessels at facilities or when being transported, are a major concern. Screening studies are performed at US sites to classify hazards posed in the event of an accidental release to the surroundings. One advantage for these facilities is that the locations of potential releases are known. During transportation, however, this is not the case as hazards may occur anywhere along the transportation route due to accidents or intentional attacks. It is well known that hazard distances estimated with simpler tools, assuming flat terrain and no obstructions, may yield nonrealitic results. Using FLACS, GexCon can help clients predict a more accurate hazard distance by taking into account necessary details like buildings, vegetation and local terrain. Another advantage of detailed CFD calculations is that the benefits from mitigation measures like fences and spill dikes can be evaluated.

 Chlorine railcar accident, terrain may be important

GexCon, using FLACS simulations, participated in the NYC tracer gas test programs. During this work, GexCon developed a frozen flow concept which significantly accelerates simulation time when modeling small amounts of released gas. By first simulating the ventilation and flow field for different wind directions our CFD dispersion calculations in Manhattan were performed faster than real time with varying wind direction based on meteorological observations. Dispersion studies like this can also be performed indoors (e.g., in shopping centres, subways, and tunnels), by specifying the actual ventilation conditions. Simulations can be used to optimize the placement of sensor systems, emergency ventilation or escape behavior.

Tracer gas dispersion studies in NYC

The FLACS simulator can also be used to effectively study pressure wave propagation indoors or in urban areas from high pressure sources, such as high explosives. FLACS can be useful in developing guidance for designs that enhance security at vulnerable locations. Below is one example of a simulation of pressure propagation from explosives in a multi-compartment building (small scale experiment by Neuwald and Reichenbach).

 Pressure propagation in multi-room building Experimental pressures (top) and FLACS simulations for 2 sensors

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