Particle Resuspension Model for Indoor Air Quality Applications

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Particle Resuspension Model for Indoor Air
Quality Applications

• Goodarz Ahmadi
• Clarkson University
• Potsdam, NY 13699
• ahmadi_at_clarkson.edu

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Outline

• Motivation and Objectives
• Adhesion and Detachment of Particles with
  elastic and
• plastic deformation
• Particle Adhesion and Detachment with
  Capillary and
• 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

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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

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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.

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Particle Resuspension from Smooth Surfaces
Forces Acting on a Particle

• Rolling Detachment
• Elastic and Plastic Deformations

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JKR Adhesion Model
Maximum Resistance to Rolling
Thermodynamic Work of Adhesion
Composite Young Modulus
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DMT and Maugis-Pollock Adhesion Model
Maximum Resistance to Rolling (DMT)
Maximum Resistance to Rolling (MP)
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Particle Resuspension
Model Predictions Results
Critical shear velocities for particle
resuspension as predicted by different adhesion
models.
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Particle Resuspension
Model Predictions Results
Critical shear velocities for particle
resuspension as predicted by different adhesion
models.
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Particle Resuspension
Model Predictions Results
Comparison of the model predcition with the
experimental data of Taheri and Bragg 39 (?)
and Ibrahim et al. 40 (?).
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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 (?).
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Resuspension of Rough Particles
Rough Particle
Rough Surface
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Resuspension of Rough Particles
Comparison of the critical shear velocities as
predicted by the burst model with the
experimental data of Zimon 38
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Bumpy Particles
Bumpy particle model of compact irregular
particles
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Electrostatic Forces for Bumpy Particles
Charge
Hays
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Bumpy Particles
Critical shear velocities for bumpy particle
resuspension in the presence of capillary and
electrostatic forces.
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Bumpy Particles
Critical shear velocities for bumpy particle
resuspension in the presence of capillary and
electrostatic forces.
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Bumpy Particles
Critical shear velocities for bumpy particle
resuspension in the presence of capillary and
electrostatic forces.
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Bumpy Particles
Critical shear velocities for bumpy particle
resuspension in the presence of capillary and
electrostatic forces.
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Bumpy Particles
Comparison of the critical electric field with
the experimental data of Hays (1978)
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Resuspension form Highly Rough Surfaces
Hydrodynamic Forces
Adhesion Force
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Sample Surface and Airflow
Velocity (m/s) Contours over a Randomly generated
surface with a roughness value of 5 micron.
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Sample Particle Removal
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Removal Areas for 2.5 µm Particles
V5m/s
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Particles Pairs Removal
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A Model for Particle Resuspension by Walking

• Assumptions
• Shoe floor contact is modeled as two circular
  disk.
• Squeezed film and wall jet models are used
  for the air flow velocity.
• Step down and up in the gait cycle are
  treated.
• Particle re-deposition is accounted for.

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Evaluation of Squeezing Velocity
Inside Foot Area (r lt R)
Outside Foot Area (r gt R)
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A Model for Particle Resuspension by Walking
Critical radius for particle detachment for
rolling detachment mechanisms at stepping down
process.
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Particle Resuspension
h2.3
t (min)
Comparison of the predicted particle
concentration with the experimental data of Ferro
and Qian (2006) for hard floor.
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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.

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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.