Task 2.B Resuspension of Dust Particles Due to Walking Y. Kubota, J. Hall, R. Sheth, H. Higuchi, M. Glauser, E. Khalifa Although the research described in this article has been funded wholly or in part by the United States Environmental Protection Agency through cooperative agreement CR , NY STAR Center for Env. Quality Systems/EPA Indoor Environmental Research Program, it has not been subjected to the Agency's required peer and policy review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred.

Contents o Background o Gait cycle u Acceleration, Deceleration, Velocity o Flow visualization u real foot motion u Idealized foot motion o PIV result u Flow field velocity u Flow velocity between foot and floor o Summary

Background PM-5 Concentration (mg/m 3 ) Ferro et al., ES&T, 2004 PM levels during a series of 15 minute human activity periods

Motivation  Particles < 10  m are easily inhaled into our lungs & can lead to poor health u Indoor human activity substantially increases indoor concentrations of PM > 1 µm (Thatcher and Layton, 1995; Abt et al., 2000; Long et al., 2000; Ferro et al., 2004) o Particles have to overcome strong adhesive forces to be resuspended: u Van der Waals forces that exist between molecules u electrostatic forces u surface tension due to moisture o All detachment models predict that a much higher velocity than that around a walking human (~1m/s) is needed to detach these size particles from a rigid floor

Flow Visualization of Real Foot Motion from Toe Camera capturing 60 frames/sec With laser to visualize plane MAE648 Biofluids Dynamics Project Instructor: H. Higuchi

Flow Visualization of Real Foot Motion from Heel Camera capturing 60 frames/sec With laser to visualize plane

Flow Visualization of Real Foot Motion from side Camera capturing 60 frames/sec With laser to visualize plane

Flow Visualization of Real Foot Motion in upward Camera capturing 60 frames/sec With laser to visualize plane

Flow Visualization of Real Foot Motion in upward

Motivation o Particles get resuspended from the floor by 2 mechanisms: u Mechanical – KE transfers to dust particles (impact, vibration) u Aerodynamic –particles become airborne by flow disturbances o Does the human stepping motion cause high enough fluid velocities to resuspend particles by aerodynamic means alone? u If so, what are the physics of the detachment mechanism? u Examine using flow visualization techniques Floor

Experimental Facility Cylindrical Coordinate fixed to the Plexiglas (floor). Z: vertical distance from the floor. For Z=0, the foot is on the floor. D is fixed for all experiments o Z f : Final vertical distance of the foot o Z i : Initial vertical distance of the foot o Uc: Constant velocity o Acc: acceleration of the movement o Dec: deceleration of the movement  x y z Foot r Plexiglas D D=6in Velocity history of foot

Flow Visualization: Downstroke, r-z plane z i = 300 [mm], z f = 1 [mm], Uc = 1 [m/s], Acc = 10 [m/s^2], Dec=-10[m/s^2] Camera capturing 60 frames/sec Arizona Dust << 10  m With laser to visualize plane

Flow Visualization: Upstroke, r-z plane z i = 300 [mm], z f = 1 [mm], Uc = 1 [m/s], Acc = 10 [m/s^2], Dec=-10[m/s^2] Camera capturing 60 frames/sec Arizona Dust << 10  m With laser to visualize plane

Measurement of Foot Motion Biofluids course project

Gait cycle: Mean Vertical Gap of Real foot motion HC: heel contact the floor, HO: heel off the floor TC: toe contact the floor, TO: Toe off the floor HO, TO HC, TC

Gait cycle: Mean Velocity of Real foot motion Upward Downward Acceleration =10.60 [m/s^2] Deceleration = [m/s^2] maximum velocity =1.875 [m/s] HC HC: Heel contact the floor

Parameters: Downward idealized foot motion for PIV o Uc = [m/s]D: Disc Diameter = 6[in] = [m] o Acc = [m/s^2] Z: Gap from the floor o Dec = [m/s^2] o Zi = 0.3 [m] o Zf = [m] Non-Dimensional Velocity history Non-Dimensional Vertical Displacement history T=2.18 T=2.34 T=3.78

PIV result: Velocity contours 0 4 [m/s]2 T=2.72, Z/D=0.492 Downward motion

0 4 [m/s]2 T=3.18, Z/D=0.184 PIV result: Velocity contours Downward motion

PIV result: Velocity contours 0 4 [m/s]2 T=3.43, Z/D=0.082 Downward motion

PIV result: Velocity contours 0 4 [m/s]2 T=3.52, Z/D=0.052 Downward motion

PIV result: Velocity contours 0 4 [m/s]2 T=3.81, Z/D= Downward motion

PIV result: Velocity contours 0 4 [m/s]2 T=4.31, Z/D= Downward motion

PIV result: Velocity contours 0 4 [m/s]2 T=4.92, Z/D= Downward motion

0 4 [m/s]2 T=2.93, Z/D= Maximum velocity = 3.87[m/s] PIV result: Velocity profile between foot and floor Downward motion

0 4 [m/s]2 T=3.18, Z/D= Maximum velocity = 3.91[m/s] PIV result: Velocity profile between foot and floor Downward motion

0 4 [m/s]2 T=3.43, Z/D= Maximum velocity = 3.95[m/s] PIV result: Velocity profile between foot and floor Downward motion

0 4 [m/s]2 T=3.47, Z/D= Maximum velocity = 3.92[m/s] PIV result: Velocity profile between foot and floor Downward motion

Gait cycle: Mean Velocity of Real foot motion Upward Downward Acceleration =13.86 [m/s^2] Deceleration =-9.55 [m/s^2] maximum velocity =1.725 [m/s] HO HC: Heel off the floor

Parameters: Upward idealized foot motion for PIV o Uc = [m/s]D: Disc Diameter = 6[in] = [m] o Acc = [m/s^2] Z: Gap from the floor o Dec = [m/s^2] o Zi = 0.3 [m] o Zf = [m] Non-Dimensional Velocity history Non-Dimensional Vertical Displacement history T=1.41 T=1.65 T=3.69

PIV result: Velocity contours 0 4 [m/s]2 T=0.57, Z/D=0.146 Upward motion

0 4 [m/s]2 T=0.85, Z/D=0.256 PIV result: Velocity contours Upward motion

PIV result: Velocity contours 0 4 [m/s]2 T=1.13, Z/D=0.455 Upward motion

PIV result: Velocity contours 0 4 [m/s]2 T=1.70, Z/D=0.994 Upward motion

CFD Results

Flow Visualization: Downstroke, r-z plane z i = 300 [mm], z f = 1 [mm], Uc = 1 [m/s], Acc = 10 [m/s^2], Dec=-10[m/s^2] Camera capturing 60 frames/sec Arizona Dust << 10  m With laser to visualize plane

Flow Visualization: Upstroke, r-z plane z i = 300 [mm], z f = 1 [mm], Uc = 1 [m/s], Acc = 10 [m/s^2], Dec=-10[m/s^2] Camera capturing 60 frames/sec Arizona Dust << 10  m With laser to visualize plane

Summary Experiment was conducted with an idealized foot motion. o The PIV measurement has shown in the downward movement, the maximum velocity occurs within the vortex and a strong wall jet is created when the foot is at the lowest position. o In the upward motion, the PIV results show a strong vortex behind the idealized foot that generates large velocity. o Both the upward and downward movements are found to be equally important for the dust resuspension and entrainment. o In the downward movement, two flow phenomena are important: the radial jet and the resulting vortex. The interaction between these shear flows and the wall causes complicated flow patterns that influence the particle redistribution o In the upward movement, particles are entrained by vortices in the disk wake o More realistic foot geometry is being tested. Other foot motions will be also examined.