Development of a predictive LES model for the study of the pollutant dispersion in urban areas

In this thesis, a new large-eddy simulation solver, LES-AIR, has been developed, tested and applied to a practical situation of flow and pollutant dispersion in urban environments. The novelty of the present research resides in the application of a high resolution, accurate, CFD technique to the simulation of real-life flows. The code uses a body fitted curvilinear grid to account for the macro geometry such as terrain slopes, and is thus able to reproduce in detail the complex conditions typical of urban areas; by utilizing the technique of immersed boundaries, the code is also able to mimic the presence the micro complexities such as anthropic structures (i.e. buildings). The first part of the thesis presents a detailed description of the mathematical and numerical model on which the code is based. An extensive set of validation tests was performed in flow configurations having an increasing degree of complexity in terms of forcing and geometry. The numerical model thus validated is applied for obtaining flow and pollutant dispersion in the Servola-Valmaura suburban area of the city of Trieste in Italy. The pollutant was introduced into the domain from a line source near the ground, mimicking the emission from vehicular traffic. In spite of the idealizations inherent to the model, LES-AIR is able to predict the flow and dispersion patterns well, and has proven to be a reliable tool for adaptation in urban pollution studies.