Large Eddy Simulation of urban dispersion

In view of an increased threat of accidental or deliberate release of hazardous substances such as industrial chemicals, radioactive releases, poisonous gas or biological agents, detailed dispersion simulations are needed. The application of dispersion modeling to an urban environment is a major simulation challenge. For a consistent simulation, a detailed geometry of the city, and a consistent treatment of such key processes as deposition and stratification, are needed. From a technical point of view, a high quality computational grid is also needed. In this work, a first urban dispersion simulation has been performed using the Large Eddy Simulation (LES). the simulation has been done for Gamla Stan in Stockholm which is well suited for model development since its location, surrounded by water, quarantees the possibility of using simple boundary conditions. Several releases have been simulated. In total, eight releases have been simulated, consisting of four different substances, released on five different locations. Taken together, all things give a true picture of the dispersion within the city, in the simulation in question.