Validation of PALM turbulence and air quality simulations using wind tunnel model measurements of a Prague traffic hotspot

Abstract

The MicroBUS project aims to evaluate the impact of traffic scenarios on the air quality of the city of Prague, through a series of methods such as a wind tunnel experiment and Computational Fluid Mechanics (CFD). In particular, the urban hotspot of Legerova street, which is an area particularly exposed to intense urban traffic, is reproduced with realistic flow fields and pollutant concentrations. This study compares the results of Legerova street wind tunnel experiment with microscale PALM model simulation’s outputs. In the experiment, the location is simulated through a physical model at a scale of 1:500. The pollution from traffic was simulated by a ground-level line source, from which passive particles or passive gas (ethane) were released at a constant emission rate. The simultaneous airflow and concentration fields were measured at a high resolution using Particle Image Velocimetry (PIV); thus, turbulent pollution fluxes were also investigated in the two street canyons of Legerova street. The particle concentration was calibrated through ethane concentrations obtained by a fast flame ionisation detector. Validation of microscale modelling in PALM is crucial for assessing the ability of the model to reproduce realistic air quality conditions.