Contaminant Transport in New York City using the coupled EL method and finite-time Lyapunov exponents

The release of contaminants in heavily populated urban locations such as New York City has become a major concern for public safety. This research addresses the transport of contaminant particles from a point source in a 2.5 km long and highly-populated area of Lower Manhattan starting just south of Battery Park. A computational grid system with approximately 76 million grid points is used to resolve the flow while the immersed boundary method is employed to resolve the geometry of the buildings, roads, and other objects including many skyscrapers of varying heights. A large eddy simulation was used to resolve the wind flow within the study area. The contaminate was modeled as particles and traced using the coupled Eulerian-Lagrangian method. We found that the windward contaminant propagation velocity was 52% of the prevailing wind velocity of 3.6 m/s. Once the pollutant source is removed, the pollutant particles propagate out of the study area at 16% of the prevailing wind velocity.