Modelling of particle resuspension by a turbulent airflow and the role of particle size, surface roughness and electric charge

Abstract

A resuspension model based on the Lennard–Jones intermolecular potential is applied to a monolayer deposit of spherical particles. The model considers the interactions between a particle and a surface under the influence of an external turbulent airflow. The particle–surface interaction was modelled with and without particle deformation due to elastic flattening. The resuspension rate was calculated by a kinetic force-balance approach whereby particle detachment occurs when the instantaneous joint contribution of the lift and drag forces exceeds the total adhesive force of the particle–surface system. Enhanced aerodynamic particle removal driven by the moment of the lift and drag forces was determined. Model predictions suggest that inclusion of the moment of the aerodynamic forces provides a suitable model for particle detachment (initiated by rolling). The importance of elastic deformation was found to depend on adhesive forces, characteristics of the substrate surface (surface roughness) and particle size. The model was applied to a number of laboratory experiments. For one set of experiments, we identified two resuspension regimes depending on whether small non-deformable or large deformable (equivalently, strongly or weakly bound) particles resuspended at high or low friction velocities. A modified model incorporating the effect of particle charge is also presented. Results indicate that particle resuspension is possible even when electrostatic forces are present, but the resuspension rate decreases considerably, depending on particle size, particle charge and surface roughness.

Keywords:

• Resuspension
• Lennard–Jones potential
• adhesion
• elastic flattening
• particle charge

Acknowledgements

This work was supported by the European Union 7th framework program HEXACOMM FP7/2007-2013 under grant agreement NO. 315760. We also thank an anonymous reviewer for numerous valuable and insightful comments that greatly improved the quality of our work and its presentation. The views expressed are purely those of the authors and may not in any circumstances be regarded as stating an official position of the European Commission.