Thesis: 3D Modelling of Air Pollution at Urban Scale

Thesis defense: Nicolas REIMINGER

Title: 3D Modelling of Air Pollution at Urban Scale

Team: MécaFlu

Abstract: The aim of this thesis is the development and the validation of Computational Fluid Dynamics (CFD) solvers and new methodologies to assess air quality in urban areas. To do so, the Unsteady Reynolds-Averaged Navier-Stokes methodology (URANS) is chosen and two new solvers are built. It includes a Forced Convection Solver (FCS) for neutral atmospheres modelling and a Mixed Convection Solver (MCS) for stable and unstable atmospheres modelling where other important phenomena such as the effects of vegetation are also considered. The results of these solvers were compared to seven test cases including wind tunnel and in situ experiments which show that an error of less than 10% can be expected on modelled concentrations, but also that indoor/outdoor exchange can be efficiently modelled. The issue of computational domain including domain extension, meshing, boundary conditions emissions and background concentrations for air quality modelling in urban areas are dealt in an improvement approach, especially in the engineering context. Numerous new methodologies are developed and validated, and their limits assessed including methodologies to assess nitrogen dioxide concentrations based on nitrogen oxides concentrations, to assess continuous wind distributions based on discrete data such as given by wind roses or to assess mean annual concentration based on punctual numerical results. The interest and potential of such numerical models and methodologies is lastly highlighted and examples of application for the purpose of design, understanding and diagnosis are presented.

The jury is composed by Pr. José Vazquez (Professeur, ENGEES, Université de Strasbourg, France)- Thesis Director, Dr. Stijn Janssen (Directeur de recherche, VITO, Mol, Belgique) - Rapporteur, Dr. Fernando Martin (Directeur de recherche, CIEMAT, Madrid, Espagne) - Rapporteur, Pr. Yannick Hoarau (Professeur, ICube, Université de Strasbourg, France), Dr. Nadège Blond (Chargée de recherche, LIVE/CNRS, Strasbourg, France), Dr. Matthieu Dufresne (Directeur scientifique 3DEAU, Strasbourg, France), Dr. Jonathan Wertel (Président 3DEAU, Strasbourg, France) and Eng. Christophe Legorgeu (Président AIR&D, Strasbourg, France).

The defense will be held in English, on September 21st at 2p.m. in the Alain Beretz amphitheatre at the new Patio on the Esplanade Campus.