Flow dynamics and pollutant transport in street canyons of different roof heights and geometries: a wind tunnel and LES modelling

Understanding the transfer of pollutants within complex urban areas is of utmost importance, but knowledge about it remains limited. This Thesis aims to investigate the characteristics of pollutant transfer, particularly flow dynamics, in six different street canyons integrated into an idealised built-up area consisting of blocks of buildings with courtyards. The systematic study was conducted to evaluate the impact of the following parameters on the ventilation of the street canyons: roof shape, building height non- uniformity and pollutant source position. Two complementary approaches are used in the study: wind-tunnel measurements and numerical modelling. In addition, a wide range of analytical methods are used, including reduced order methods such as Proper Orthogonal Decomposition (POD) and Oscillation Pattern Decomposition (OPD). It is shown that the OPD method provides valuable insights into the ventilation dynamics of street canoyns. The results demonstrate that all the parameters investigated have a significant impact on the ventilation, with roof shape playing a comparatively smaller role for non-uniform street canyons. All the methods applied have contributed to a better understanding of the observed processes while shedding light on the physical implications of the data decomposition methods by..