Author(s)

NADA TAOUIL, DESMOND H. LIM, MOHAMMAD JADIDI, MAHDI AZARPEYVAND

Abstract

Accurate representation of urban airflow and pollutant dispersion is essential for effective air quality assessment and management. Wind tunnel experiments are widely used to investigate these processes. However, many existing studies rely on idealised flat terrain city models that neglect the influence of realistic urban topography, such as hills and valleys. This study presents an experimental investigation of pollutant dispersion over a scaled physical model of the city of Bristol that incorporates realistic terrain topography. Wind tunnel measurements were conducted in the University of Bristol Boundary Layer Wind Tunnel with urban approaching atmospheric boundary layer conditions. The urban model includes detailed elevation changes and underlying landform features together with representative building geometry. Pollutant dispersion was simulated using a passive tracer gas, with mean concentration fields measured using a fast flame ionisation detector. Simultaneous hot-wire anemometry measurements provided detailed characterisation of the velocity field and turbulence structure, enabling direct coupling between flow and concentration data. The results reveal the significant influence of complex terrain on urban airflow patterns and pollutant distribution. The measured flow structures and concentration fields demonstrate strong spatial variability associated with elevation changes, highlighting the sensitivity of dispersion processes to realistic terrain representation. These findings provide experimental evidence supporting the need to incorporate topographic complexity in physical modelling studies and offer valuable data for dispersion model validation and improved urban air quality assessment in cities with complex terrain.

Keywords

urban airflow, pollutant dispersion, complex terrain, boundary layer wind tunnel, urban air quality