Applied numerical modeling of transport and dispersion in subway systems

Subway systems are widely recognized as attractive targets for airborne chemical and biological terrorism attacks due to the presence of large populations in confined spaces and necessarily limited security. For cities with substantial subway systems, the subway dispersion problem is integral to an overall urban dispersion modeling framework since materials released in the subway not only generate hazards within the subway itself, but also and throughout the city as a whole since materials released in the subway are ejected to the outdoors through vents, station entrances and other openings to the exterior and then carried by the wind. Furthermore, materials released outdoors can be drawn into the subway and carried upwind or crosswind of the release point creating hazards at locations that emergency response personnel might believe are safe.

In this presentation, we discuss the transport and fate of both gaseous and particulate materials within subway systems. We examine the overall phenomenology of the problem and highlight the important physical transport mechanisms involved. We then discuss modeling techniques, primarily focusing on the ANL Below Ground Model. This subway transport and dispersion model has been developed over the past decade to address a variety of applications ranging from threat assessment scenario analyses to helping establish and refine requirements for chemical and biological detection systems.