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.

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.

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.

Flow Visualization of Axisymmetric Impinging Jet on a Concave Surface

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Dong Hwan Shin ◽  
Yeonghwan Kim ◽  
Jin Sub Kim ◽  
Do Won Kang ◽  
Jeong Lak Sohn ◽  
...  
Keyword(s):  
Flow Visualization ◽  
Large Scale ◽  
Impinging Jet ◽  
Ambient Air ◽  
Concave Surface ◽  
Small Scale ◽  
Wall Jet ◽  
Entrainment Rate ◽  
Toroidal Vortex ◽  
Axisymmetric Jet

Flow visualization was performed to give a physical insight with vortical structures of an axisymmetric impinging jet on a concave surface. High-speed imaging was employed to get clear images with a laser light sheet illumination. An axisymmetric jet is issued into quasi-ambient air through a straight pipe nozzle with fully-developed velocity profile. A regular vertical pattern of an axisymmetric jet was observed with different flow entrainment rate. While an impinged jet turns to convert a wall jet along a concave surface, the flow interaction between the large-scale toroidal vortex and the concave surface was observed in the transition between the stagnation and wall jet zone. The ring-shaped wall eddies induced from a pair of toroidal vortices were also appeared to diverge into the radial direction along the concave surface. As the jet Reynolds number increases, small-scale vortices can be developed to a large-scale toroidal vortex. The location in which a large-scale toroidal vortex strikes is generally identical to the location where the secondary peak in heat transfer occurs. The frequency of large scale toroidal vortex on concave surface is found to be nearly similar as that of wall jet on flat surface. As the nozzle-to-target spacing (L/D) increases, it becomes shorter due to the loss of jet momentum. The flow behavior of axisymmetric impinging jet on a concave surface can be helpful to design the internal passage cooling for gas turbine blade.

scholarly journals Implications of the COVID-19 Lockdown on Dengue Transmission in Malaysia

2021 ◽  
Vol 13 (1) ◽  
pp. 148-160
Author(s):  
Song-Quan Ong ◽  
Hamdan Ahmad ◽  
Ahmad Mohiddin Mohd Ngesom
Keyword(s):  
Large Scale ◽  
Moving Average ◽  
Human Movement ◽  
Population Movement ◽  
Sarima Model ◽  
Autoregressive Integrated Moving Average ◽  
Predominant Species ◽  
Lower Confidence ◽  
Dengue Transmission ◽  
Stage 1

We aim to investigate the effect of large-scale human movement restrictions during the COVID-19 lockdown on both the dengue transmission and vector occurrences. This study compared the weekly dengue incidences during the period of lockdown to the previous years (2015 to 2019) and a Seasonal Autoregressive Integrated Moving Average (SARIMA) model that expected no movement restrictions. We found that the trend of dengue incidence during the first two weeks (stage 1) of lockdown decreased significantly with the incidences lower than the lower confidence level (LCL) of SARIMA. By comparing the magnitude of the gradient of decrease, the trend is 319% steeper than the trend observed in previous years and 650% steeper than the simulated model, indicating that the control of population movement did reduce dengue transmission. However, starting from stage 2 of lockdown, the dengue incidences demonstrated an elevation and earlier rebound by four weeks and grew with an exponential pattern. We revealed that Aedes albopictus is the predominant species and demonstrated a strong correlation with the locally reported dengue incidences, and therefore we proposed the possible diffusive effect of the vector that led to a higher acceleration of incidence rate.

scholarly journals 1068. Large-Scale Migration and the Changing Viral Hepatitis Prevalences in North America: A modeling approach

2020 ◽  
Vol 7 (Supplement_1) ◽  
pp. S563-S563
Author(s):  
Kenneth A Valles ◽  
Lewis R Roberts
Keyword(s):  
United States ◽  
Viral Hepatitis ◽  
Large Scale ◽  
Country Of Origin ◽  
Human Movement ◽  
High Volume ◽  
The United States ◽  
The Philippines ◽  
Outcome Data ◽  
Treatment Programs

Abstract Background Infection by hepatitis B and C viruses causes inflammation of the liver and can lead to cirrhosis, liver failure, and hepatocellular carcinoma. The WHO’s ambition to eliminate viral hepatitis by 2030 requires strategies specific to the dynamic disease profiles each nation faces. Large-scale human movement from high-prevalence nations to the United States and Canada have altered the disease landscape, likely warranting adjustments to present elimination approaches. However, the nature and magnitude of the new disease burden remains unknown. This study aims to generate a modeled estimate of recent HBV and HCV prevalence changes to the United States and Canada due to migration. Methods Total migrant populations from 2010-2019 were obtained from United Nations Migrant Stock database. Country-of-origin HBV and HCV prevalences were obtained for the select 40 country-of-origin nations from the Polaris Observatory and systematic reviews. A standard pivot table was used to evaluate the disease contribution from and to each nation. Disease progression estimates were generated using the American Association for the Study of the Liver guidelines and outcome data. Results Between 2010 and 2019, 7,676,937 documented migrants arrived in US and Canada from the selected high-volume nations. Primary migrant source regions were East Asia and Latin America. Combined, an estimated 878,995 migrants were HBV positive, and 226,428 HCV positive. The majority of both migrants (6,477,506) and new viral hepatitis cases (HBV=840,315 and HCV=215,359) were found in the United States. The largest source of HBV cases stemmed from the Philippines, and HCV cases from El Salvador. Conclusion Massive human movement has significantly changed HBV and HCV disease burdens in both the US and Canada over the past decade and the long-term outcomes of cirrhosis and HCC are also expected to increase. These increases are likely to disproportionally impact individuals of the migrant and refugee communities and screening and treatment programs must be strategically adjusted in order to reduce morbidity, mortality, and healthcare expenses. Disclosures All Authors: No reported disclosures

Experimental investigation of a plane wall jet subjected to an external lateral flow

2015 ◽  
Vol 56 (5) ◽  
Author(s):  
Ahmed Kaffel ◽  
Jean Moureh ◽  
Jean-Luc Harion ◽  
Serge Russeil
Keyword(s):  
Experimental Investigation ◽  
Lateral Flow ◽  
Plane Wall ◽  
Wall Jet
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