Particle Resuspension Model for Indoor Air Quality Applications Goodarz Ahmadi Clarkson University Potsdam, NY

SAC Review 07/26-27/ Outline o Motivation and Objectives o Adhesion & Detachment of Particles with elastic & Plastic deformation o Particle Adhesion & Detachment with Capillary & Electrostatic Forces o Particle Removal from Rough Surfaces: u Small Roughness u Bumpy Particles u Highly Rough Surfaces o Particle Removal due to Human Walking u Model Description u Sample Results o Conclusions and Future work

SAC Review 07/26-27/ Motivation and general Objectives o Concentrations of particle pollutants in the indoor environment are often higher than outdoor. Particle resuspension due to human activity is expected to be one cause for the increase in PM. o Primary goal of this thrust is to provide quantitative understanding of the contribution of particle resuspension to PM concentration in the indoor environment

SAC Review 07/26-27/ Specific Objectives o Develop a particle detachment/re-suspension model for spherical and non-spherical particles from surfaces in the presence of capillary and electrostatic forces for indoor air quality applications. o To validate the detachment/re-suspension model. o To Develop a user defines subroutine for implementation of the model in the CFD codes. o To asses the contribution of the resuspension to the increase in indoor PM concentration due to human activities.

SAC Review 07/26-27/ Particle Resuspension from Smooth Surfaces Forces Acting on a Particle  Rolling Detachment  Elastic and Plastic Deformations

SAC Review 07/26-27/ Maximum Resistance to Rolling JKR Adhesion Model Thermodynamic Work of Adhesion Composite Young Modulus

SAC Review 07/26-27/ Maximum Resistance to Rolling (DMT) DMT and Maugis-Pollock Adhesion Model Maximum Resistance to Rolling (MP)

SAC Review 07/26-27/ Particle Resuspension Critical shear velocities for particle resuspension as predicted by different adhesion models. Model Predictions Results Polystyrene- Polystyrene Burst, Rolling JKR DMT Maugis-Pollock d (μm)

SAC Review 07/26-27/ Particle Resuspension Model Predictions Results d (μm) Calcium Carbonate- Calcium Carbonate Burst, Rolling With Capillary JKR DMT Maugis-Pollock Critical shear velocities for particle resuspension as predicted by different adhesion models.

SAC Review 07/26-27/ Particle Resuspension Model Predictions Results Comparison of the model predcition with the experimental data of Taheri and Bragg [39] (□) and Ibrahim et al. [40] (○). d (μm) Glass-Glass Burst, Rolling JKR DMT Maugis-Pollock With Capillary Without Capillary □ Taheri and Bragg [39] ○ Ibrahim et al. [40]

SAC Review 07/26-27/ Particle Resuspension Model Predictions Results Comparison of the model predictions with the experimental data of Zimon [38] (□), Ibrahim et al. [40] (○) and Ibrahim et al. [41] (◊). d (μm) Glass-Steel Burst, Rolling JKR DMT Maugis-Pollock With Capillary Without Capillary □ Zimon [38] ○ Ibrahim et al. [40] ◊ Ibrahim et al. [41]

SAC Review 07/26-27/ mg Resuspension of Rough Particles mg

SAC Review 07/26-27/ Comparison of the critical shear velocities as predicted by the burst model with the experimental data of Zimon [38] Resuspension of Rough Particles

SAC Review 07/26-27/ Bumpy Particles Bumpy particle model of compact irregular particles

SAC Review 07/26-27/ Charge Hays Electrostatic Forces for Bumpy Particles

SAC Review 07/26-27/ Bumpy Particles Critical shear velocities for bumpy particle resuspension in the presence of capillary and electrostatic forces.

SAC Review 07/26-27/ Bumpy Particles Critical shear velocities for bumpy particle resuspension in the presence of capillary and electrostatic forces.

SAC Review 07/26-27/ Bumpy Particles Critical shear velocities for bumpy particle resuspension in the presence of capillary and electrostatic forces.

SAC Review 07/26-27/ Bumpy Particles Critical shear velocities for bumpy particle resuspension in the presence of capillary and electrostatic forces.

SAC Review 07/26-27/ Bumpy Particles Comparison of the critical electric field with the experimental data of Hays (1978)

SAC Review 07/26-27/ Resuspension form Highly Rough Surfaces Adhesion Force Hydrodynamic Forces

SAC Review 07/26-27/ Sample Surface and Airflow Velocity (m/s) Contours over a Randomly generated surface with a roughness value of 5 micron.

SAC Review 07/26-27/ Sample Particle Removal

SAC Review 07/26-27/ Removal Areas for 2.5 µm Particles V = 5 m/s

SAC Review 07/26-27/ Particles Pairs Removal

SAC Review 07/26-27/ A Model for Particle Resuspension by Walking Assumptions o Shoe floor contact is modeled as two circular disks. o Squeezed film and wall jet models are used for the air low velocity. o Step down and up in the gait cycle are treated. o Particle re-deposition is accounted for.

SAC Review 07/26-27/ Evaluation of Squeezing Velocity Inside Foot Area (r < R) Outside Foot Area (r > R)

SAC Review 07/26-27/ A Model for Particle Resuspension by Walking Squeezed Film Wall Jet Critical radius for particle detachment for rolling detachment mechanisms at stepping down process.

SAC Review 07/26-27/ Particle Resuspension __ Simulation d=3~4μm x--- Experiment d=3~4μm __ Simulation d=5~7.5μm *--- Experiment d=5~7.5μm h=2.3 Comparison of the predicted particle concentration with the experimental data of Ferro and Qian (2006) for hard floor. t (min)

SAC Review 07/26-27/ Conclusions o A particle resuspension model from smooth and rough surfaces in presence of capillary force and electrostatic forces was developed. o The model was applied to particle resuspension in indoor environment due to human activities. o Preliniary comparisons with experimental data was performed.

SAC Review 07/26-27/ Future Work o Validate the model against additional data. o Perform detailed analysis of particle resuspenion in indoor environment due to human activities. o Develop detailed effect of large surface roughness on particle resuspension. o Develop a user defines subroutine for implementation of the model in the CFD codes. o Develop a model for resuspension form carpeted surfaces.