Implementation of a particle resuspension model in a Large Eddy Simulation code

In urban areas, pollutant deposition leads to the accumulation of particles on surfaces. These particles include emissions from traffic, heavy metals, micro-plastics and other debris. In the right meteorological conditions, these pollutants can be detached from the surface and resuspended, adversely affecting air quality near the ground and directly exposing city inhabitants. Soil resuspension was found to be a lingering cause of lead exposure for children in several US cities [1]. With the advent of electrical vehicles, indirect sources such as resuspension will become greater contributors to air pollution.

However, quantifying the contribution of resuspension to pollutant exposure remains challenging. Field studies often rely on indirect measurement methods, and wind tunnel experiments use simplified topologies. Computational fluid dynamics tools (CFD) have been employed in only a few studies, with even fewer utilizing the Large Eddy Simulation (LES) framework.

Here we present the coupling of a particle resuspension model to PALM, an open-source LES code. Resuspension is simulated according to the Rock’n’Roll model [2], a probability based approach estimating the resuspension rate from macroscopic properties. The originality of the coupling is that the distribution of adhesion forces is discretized. This allows resuspension to interact with deposition, which is crucial to apply the Rock’n’Roll model to urban air quality studies.

The coupling has been validated against experimental data from [2]. Further validation is planned against more recent datasets, paving the way for the expansion of the Rock’n’Roll model to include effects such as surface roughness [3], flow acceleration [4] and non-spherical particles. We will discuss preliminary results obtained in the case of a street canyon, offering insights into resuspension dynamics in urban environments. Our work aims to provide guidelines to create healthier urban environments and understand how evolving transportation technologies will shape pollutant exposure patterns.

 

[1] M. Laidlaw, G. Filippelli, Resuspension of urban soils as a persistent source of lead poisoning in children: A review and new directions, Applied Geochemistry, Volume 23, Issue 8,  2021-2039, (2008).

[2] M.W. Reeks, D. Hall, Kinetic models for particle resuspension in turbulent flows: theory and measurement, Journal of Aerosol Science, Volume 32, Issue 1, 1-31, (2001).

[3] S. Peillon et al., Adhesion forces of radioactive particles measured by the Aerodynamic Method–Validation with Atomic Force Microscopy and comparison with adhesion models, Journal of Aerosol Science, Volume 165, (2022).

[4] C. Cazes, Resuspension of microparticles in the air induced by transient events in the flow, experimental approach, Ecole nationale supérieure Mines-Telecom Atlantique, (2023)