Particle Resuspension Model for Indoor Air Quality Applications

1. Goodarz Ahmadi Clarkson University ahmadi@clarkson.edu Particle Resuspension Model for Indoor Air Quality Applications

2. Outline • Motivation and Objectives • Adhesion & Detachment of Particles with elastic & Plastic deformation • Particle Adhesion & Detachment with Capillary & Electrostatic Forces • Particle Removal from Rough Surfaces: • Small Roughness • Bumpy Particles • Highly Rough Surfaces • Particle Removal due to Human Walking • Model Description • Sample Results • Conclusions and Future work

3. Motivation and general Objectives • 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. • Primary goal of this thrust is to provide quantitative understanding of the contribution of particle resuspension to PM concentration in the indoor environment

4. Specific Objectives • 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. • To validate the detachment/re-suspension model. • To Develop a user defines subroutine for implementation of the model in the CFD codes. • To asses the contribution of the resuspension to the increase in indoor PM concentration due to human activities.

5. Particle Resuspension from Smooth Surfaces Forces Acting on a Particle • Rolling Detachment • Elastic and Plastic Deformations

6. JKR Adhesion Model Maximum Resistance to Rolling Thermodynamic Work of Adhesion Composite Young Modulus

7. DMT and Maugis-Pollock Adhesion Model Maximum Resistance to Rolling (DMT) Maximum Resistance to Rolling (MP)

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

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

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

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

12. Resuspension of Rough Particles mg mg Rough Surface Rough Particle

13. Resuspension of Rough Particles Comparison of the critical shear velocities as predicted by the burst model with the experimental data of Zimon [38]

14. Bumpy Particles Bumpy particle model of compact irregular particles

15. Electrostatic Forces for Bumpy Particles Charge Hays

16. Bumpy Particles Critical shear velocities for bumpy particle resuspension in the presence of capillary and electrostatic forces.

17. Bumpy Particles Critical shear velocities for bumpy particle resuspension in the presence of capillary and electrostatic forces.

18. Bumpy Particles Critical shear velocities for bumpy particle resuspension in the presence of capillary and electrostatic forces.

19. Bumpy Particles Critical shear velocities for bumpy particle resuspension in the presence of capillary and electrostatic forces.

20. Bumpy Particles Comparison of the critical electric field with the experimental data of Hays (1978)

21. Resuspension form Highly Rough Surfaces Hydrodynamic Forces Adhesion Force

22. Sample Surface and Airflow Velocity (m/s) Contours over a Randomly generated surface with a roughness value of 5 micron.

23. Sample Particle Removal

24. Removal Areas for 2.5 µm Particles V = 5 m/s

25. Particles Pairs Removal

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

27. Evaluation of Squeezing Velocity Inside Foot Area (r < R) Outside Foot Area (r > R)

28. A Model for Particle Resuspension by Walking Wall Jet Squeezed Film Critical radius for particle detachment for rolling detachment mechanisms at stepping down process.

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

30. Conclusions • A particle resuspension model from smooth and rough surfaces in presence of capillary force and electrostatic forces was developed. • The model was applied to particle resuspension in indoor environment due to human activities. • Preliniary comparisons with experimental data was performed.

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