Numerical simulation and analysis of hazardous gas dispersion in urban sub-domain

Accidental release of hazardous gases in densely populated urban areas constitutes a severe threat to public health and safety. For effective emergency preparedness and loss prevention purpose, this paper describes a high-resolution computational fluid dynamics (CFD) approach, loosely coupled with GIS, to model and simulate gas dispersion at the building to city blocks scale. Real layout and heights of buildings are obtained through digitalized maps and GIS. With the treatment of the complicated canopy catalog and the boundary conditions, a three-dimensional model solving the Reynolds averaged Navier-Stokes equations with k-ε turbulence closure is established and performed to study the flow field and concentration distributions around the complex arrangement of buildings. For illustration purposes, the dispersion of chlorine released from a chemical plant over the surrounding residential area is simulated, and the influences of meteorological conditions on the dispersion are also discussed.