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Velocity and concentration fields have been measured simultaneously in the water channel to quantify the turbulent dispersion of a passive tracer emitted at street level by a line source within an idealised urban canyon. The experiment has been conducted for an arrangement of two-dimensional obstacles with aspect ratio unity. Statistical moments of velocity and concentration have been calculated with high spatial resolution. Furthermore, the simultaneous measure of velocity and concentration at the same point made it possible to determine the tracer flux in the whole domain as well as to quantify the removal and re-entrainment of the pollutant through the canyon top. [ABSTRACT FROM AUTHOR]

This paper presents a water-channel simulation of flow and turbulence in the urban boundary layer. The goal is to assess the role played by the aspect ratio (AR) of the street canyon, assumed as an archetype for more complex and realistic urban fabrics. The physical model consists of a series of two-dimensional obstacles used to mimic a regular array of buildings. Velocity measurements are performed using image analysis. Results show a dependence of the mean velocity and turbulence parameters on AR. Attention is particularly focused on the turbulent kinetic energy and its production-advection-dissipation mechanisms that occur in the urban canopy. [ABSTRACT FROM AUTHOR]

This paper presents a water-channel simulation of flow and turbulence in the urban boundary layer. The goal is to assess the role played by the aspect ratio (AR) of the street canyon, assumed as an archetype for more complex and realistic urban fabrics. The physical model consists of a series of two-dimensional obstacles used to mimic a regular array of buildings. Velocity measurements are performed using image analysis. Results show a dependence of the mean velocity and turbulence parameters on AR. Attention is particularly focused on the turbulent kinetic energy and its production-advection-dissipation mechanisms that occur in the urban canopy. [ABSTRACT FROM AUTHOR]