Aerodynamic Particle Resuspension due to Human and Model Foot Motions

2010 ◽  
Author(s):  
Yoshihiro Kubota ◽  
Hiroshi Higuchi
Keyword(s):  
Flow Visualization ◽  
Particle Concentration ◽  
Three Dimensional ◽  
Wall Jet ◽  
Piv Measurements ◽  
Particle Resuspension ◽  
Human Foot ◽  
Image Velocimetry ◽  
Foot Motion ◽  
Foot Tapping

Human foot motions such as walking and foot tapping detach the particulate matter on the floor and redistribute it, increasing the particle concentration in air. The objective of this paper is to experimentally investigate the mechanism of particle resuspension and redistribution due to human foot motion. In particular, generation and deformation of vortex produced by the foot motion and how they are affected by the shape of sole have been examined. The experiments were carried out by particle flow visualization and the Particle Image Velocimetry (PIV) measurements in air, and dye flow visualization in water. The flow visualizations with human foot tapping and stomping were also carried out in order to elucidate the particle resuspension in real situations. In a laboratory experiment, the foot was modeled either as an elongated plate or a foot wearing a slipper, moving normal to the ground downward or upward. To focus on the aerodynamic effect, the model foot was stopped immediately above the floor before contacting the floor. The results indicated that the particles were resuspended both in downward motion and in upward motion of the foot. The particle resuspension and redistribution were associated with the wall jet between the foot and floor and the vortex dynamics. With an elongated plate, three-dimensional vortex structure strongly affected the particle redistribution.

Experimental Study of Three-Dimensional Laminar Wall Jets of Non-Newtonian Fluid

2009 ◽  
Author(s):  
Kofi K. Adane ◽  
Mark F. Tachie
Keyword(s):  
Newtonian Fluid ◽  
Open Channel ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Jet Flows ◽  
Wall Jet ◽  
Particle Image Velocimetry Technique ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Shear Thinning Fluid

A particle image velocimetry technique was employed to study three-dimensional laminar wall jet flows of a non-Newtonian shear-thinning fluid. The wall jet was created using a circular pipe of diameter 7 mm and flows into an open channel. The Reynolds numbers based on the pipe diameter and jet exit velocity were varied from 250 to 800. The PIV measurements were performed in various streamwise-transverse and streamwise-spanwise planes. From these measurements, the velocity profiles, jet growth rate and spread rates were obtained to study the characteristics of three-dimensional wall jet flows of a non-Newtonian fluid.

PIV Measurements of the Turbulent Secondary Flow in a Three-Dimensional Wall Jet

2010 ◽  
Author(s):  
Lhendup Namgyal ◽  
Joseph W. Hall
Keyword(s):  
Secondary Flow ◽  
Reynolds Shear Stress ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Half Width ◽  
Wall Jet ◽  
Normal Stresses ◽  
Reynolds Stresses ◽  
Piv Measurements ◽  
Image Velocimetry

The lateral half width of the turbulent three-dimensional wall jet is typically five to eight times larger than the vertical half width normal to the wall. Although, the reason for this behavior is not fully understood, it is known to be caused by strong secondary flows that develop in the jet due to presence of the wall. The source of the secondary flow in the jet has been attributed previously with both mean vorticity reorientation and to anisotropy in the Reynolds normal stresses, but until now there have been no measurements of these quantities in this flow. Particle Image Velocimetry (PIV) measurements are used herein to measure the Reynolds stresses that contribute to the secondary flow in a turbulent three-dimensional wall jet formed using a circular contoured nozzle with exit Reynolds number of 250,000. In particular, the Reynolds shear stress, vw was found to be significantly smaller throughout the jet than the differences in the Reynolds normal stresses (v2 − w2).

An Experimental Investigation of the Flowfield and Dust Resuspension Due to Idealized Human Walking

2009 ◽  
Vol 131 (8) ◽  
Author(s):  
Yoshihiro Kubota ◽  
Joseph W. Hall ◽  
Hiroshi Higuchi
Keyword(s):  
Flow Visualization ◽  
Large Scale ◽  
Outer Edge ◽  
Human Walking ◽  
Ring Vortex ◽  
Particle Resuspension ◽  
Human Foot ◽  
Image Velocimetry ◽  
Walking Motion ◽  
Dust Resuspension

In order to address how human foot movement causes particles to be resuspended from the floor, particle flow visualization and particle image velocimetry (PIV) measurements were performed on a simplified model of the human walking motion; a disk moving normal to the floor. Flow visualization of particles, seeded initially on the ground, indicates that particles are resuspended by both the downward and upward motions of the walking process. On both the upstep and the downstep, particle resuspension occurs due to a high velocity wall jet, forming between the wall and the disk in general accord with the mechanism for particle resuspension put forth by Khalifa and Elhadidi (2007, “Particle Levitation Due to a Uniformly Descending Flat Object,” Aerosol Sci. Technol., 41, pp. 33–42). Large-scale ring vortex structures were formed on both the downstep and the upstep, and did not cause particle resuspension, but were extremely effective at quickly moving the already resuspended particles away from the wall. By varying the seeding of the particles, it was determined that only particles underneath and toward the outer edge of the disk are resuspended.

An Experimental Investigation of the Flowfield and Dust Resuspension Due to Idealized Human Walking: Disk Model

2007 ◽  
Author(s):  
Yoshihiro Kubota ◽  
Joseph W. Hall ◽  
Hiroshi Higuchi
Keyword(s):  
Experimental Investigation ◽  
Flow Visualization ◽  
Large Scale ◽  
Human Movement ◽  
Human Walking ◽  
Wall Jet ◽  
Disk Model ◽  
Piv Measurements ◽  
Particle Resuspension ◽  
Dust Resuspension

To better understand how human movement causes particles to be resuspended from the ground, we performed flow visualization and PIV measurements on idealized human walking, a disk moved normal to the ground. The flow visualization indicates that particles are resuspended on both the down step and the up step of the walking process by a purely aerodynamic mechanism. The results suggest that a wall jet formed beneath the disk is responsible for particle resuspension, whereas large scale vortices created in the wake of the disk are responsible for the rapid redistribution of the resuspended particles.

PIV Measurements in Diffuser of the Radial Pump

2015 ◽  
Author(s):  
Sung Yong Jung ◽  
Young Uk Min ◽  
Kyung Lok Lee
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Internal Flows ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Acquisition Device ◽  
Field Information ◽  
Radial Pump

The performance characteristics of the radial pump commonly used as a multistage (8 or 10 stage) pump have been investigated experimentally. Due to the complex three-dimensional geometries, the hydraulic performance of multistage pumps is closely related to the internal flows in diffuser and return vanes. In order to investigate the flow characteristics in these regions by Particle Image Velocimetry (PIV) technique, a transparent pump is designed. A 532 nm continuous laser and a high-speed camera are used as a light source and an image acquisition device, respectively. The velocity field information in a diffuser of the radial pump is successfully obtained by two-dimensional PIV measurements at various operating conditions.

scholarly journals Flow Visualization of a Three-Dimensional Wall Jet using the Tuft-Grid Method

2007 ◽  
Vol 27 (Supplement2) ◽  
pp. 51-52
Author(s):  
Haruhisa YANO ◽  
Kai OU ◽  
Yoshihiro INOUE ◽  
Shintaro YAMASHITA
Keyword(s):  
Flow Visualization ◽  
Three Dimensional ◽  
Grid Method ◽  
Wall Jet

Experimental and Numerical Study of the Flow Around a Semi-Submerged Rectangular Cylinder

2012 ◽  
Author(s):  
Tufan Arslan ◽  
Stefano Malavasi ◽  
Bjørnar Pettersen ◽  
Helge I. Andersson
Keyword(s):  
Particle Image ◽  
Model Simulation ◽  
Numerical Study ◽  
Three Dimensional ◽  
Separated Flow ◽  
Piv Measurements ◽  
Rectangular Cylinder ◽  
Image Velocimetry ◽  
Computational Fluid Dynamics Cfd

The present work is motivated by phenomena occurring in the flow field around structures partly submerged in water. A three dimensional unsteady flow around a rectangular cylinder is studied for four different submergence ratios by using computational fluid dynamics (CFD) tools with LES turbulence model. Simulation results are compared to particle image velocimetry (PIV) measurements at Reynolds number Re = 12100 and Froude number Fr = 0.26. Focus in our investigation is on the characterization of the behaviour of vortex structures generated by separated flow. Another target in the study is to obtain better knowledge of the hydrodynamic forces acting on a semi-submerged structure. Computed force coefficients are compared with experimental measurements.

Human foot tapping-induced particle resuspension in indoor environments: Flooring hardness effect

2019 ◽  
Vol 29 (2) ◽  
pp. 230-239 ◽  
Author(s):  
Ahmed Benabed ◽  
Karim Limam ◽  
Bart Janssens ◽  
Walter Bosschaerts
Keyword(s):  
Ceramic Tile ◽  
Gait Cycle ◽  
Experimental Chamber ◽  
Indoor Environments ◽  
Emission Rates ◽  
Mass Balance Equation ◽  
Particle Resuspension ◽  
Human Foot ◽  
Foot Tapping ◽  
Number Of Particles

Particle resuspension due to human foot tapping (the landing phase of the foot during the gait cycle) was experimentally studied in a 25 cm (W) × 25 cm (H) × 50 (L) experimental chamber. The foot tapping was modelled using a free rotation toward the floor of a wooden rectangular plate (8 cm (W) × 22 cm (L)). Flooring included ceramic tile, hardwood, PVC tile, vinyl, and two different linoleum samples were utilized. Particle resuspension source strengths were estimated using the mass balance equation. Source strength (emission rates in number of particles per time) ranged from 4 particles/s to 0.05 particles/s. For 0.5–0.65 µm particles, the source strengths in the case of the ceramic tile are 2.5 times greater than those of the PVC tile and eight times greater than those of linoleum flooring. The results show that particles source strengths increase with flooring hardness. However, flooring roughness shows no significant influence on particle resuspension.

scholarly journals Flow control with rotating cylinders

2017 ◽  
Vol 825 ◽  
pp. 743-763 ◽  
Author(s):  
James C. Schulmeister ◽  
J. M. Dahl ◽  
G. D. Weymouth ◽  
M. S. Triantafyllou
Keyword(s):  
Reynolds Number ◽  
Flow Control ◽  
Three Dimensional ◽  
Rotating Cylinders ◽  
Piv Measurements ◽  
Rotation Rates ◽  
Image Velocimetry ◽  
The Mean ◽  
Recirculation Length ◽  
Control Cylinder

We study the use of small counter-rotating cylinders to control the streaming flow past a larger main cylinder for drag reduction. In a water tunnel experiment at a Reynolds number of 47 000 with a three-dimensional and turbulent wake, particle image velocimetry (PIV) measurements show that rotating cylinders narrow the mean wake and shorten the recirculation length. The drag of the main cylinder was measured to reduce by up to 45 %. To examine the physical mechanism of the flow control in detail, a series of two-dimensional numerical simulations at a Reynolds number equal to 500 were conducted. These simulations investigated a range of control cylinder diameters in addition to rotation rates and gaps to the main cylinder. Effectively controlled simulated flows present a streamline that separates from the main cylinder, passes around the control cylinder, and reattaches to the main cylinder at a higher pressure. The computed pressure recovery from the separation to reattachment points collapses with respect to a new scaling, which indicates that the control mechanism is viscous.

Sign in / Sign up

Export Citation Format

Share Document