High Resolution Investigations into Non-Ideal Resuspension Phenomena

EDWARD NEAL, Barnaby Miles, Lukesh Mahato, Richard J. Thomas, Maurice Walker, Jack Vincent, Simon Parker, Virginia Foot, Emily Kruger, Jonathan P. Reid, University of Bristol

     Abstract Number: 269
     Working Group: Aerosol Physics

Abstract
Particle resuspension is omnipresent in our lives with activities such as cleaning, walking, and driving, all contributing to resuspended aerosol concentrations. Existing mechanistic models for resuspension, however, have limited complexity due to a lack of understanding on contributing factors and are neglected in aerosol dispersion models. This research explores two scenarios that can influence resuspension rates, non-spherical particle morphologies and particle-particle collisions, utilizing wind tunnel studies at 100 frames per second (FPS) and high frame rate imaging at 30000 FPS to explore collective and single particle resuspension events.

A novel methodology (Neal et al., Submitted 2024) is employed to investigate the impact of particle-specific features on resuspension, partnering a quadrupole electrodynamic trap for controlled particle fabrication and deposition (the QuadFab) with a small-scale 3D printed wind tunnel. Within the QuadFab, aerosol droplets are suspended and dried under controlled relative humidity (RH) conditions. Varying this RH adapts the morphology of the resulting particles that are subsequently deposited and resuspended in the wind tunnel. Resuspension efficiencies for two morphologies of sodium chloride particles, exhibiting raspberry-shaped and cubic morphologies, will be presented. The difference between the resuspension of these morphologies is further explored with high frame rate imaging of individual resuspension events. This technique allows for greater resolution analysis of particle orientation, particle-surface contact and rotation during resuspension.

Finally, during validation experiments with spherical glass standards the tendency for particles to collide and produce cascading resuspension events was identified as a potential source of increased resuspension (Neal et al., Submitted 2024). A collision-focused analysis of these glass standard resuspensions is now presented that evaluates collision angles and distances, benefiting from the high temporal resolution of the wind tunnel apparatus. By probing both morphology and collision related phenomena this research aims to increasingly untangle the complex mixture of factors that contribute to particle resuspension.