This study presents results from a vegetation-induced flow experimental study which investigates 3-D turbulence structure profiles,including Reynolds stress,turbulence intensity and bursting analysis of open channel f...This study presents results from a vegetation-induced flow experimental study which investigates 3-D turbulence structure profiles,including Reynolds stress,turbulence intensity and bursting analysis of open channel flow.Different vegetation densities have been built between the adjacent vegetations,and the flow measurements are taken using acoustic Doppler velocimeter(ADV)at the locations within and downstream of the vegetation panel.Three different tests are conducted,where the first test has compact vegetations,while the second and the third tests have open spaces created by one and two empty vegetation slots within the vegetated field.Observation reveals that over 10%of eddies size is generated within the vegetated zone of compact vegetations as compared with the fewer vegetations.Significant turbulence structures variation is also observed at the points in the non-vegetated row.The findings from burst-cycle analysis show that the sweep and outward interaction events are dominant,where they further increase away from the bed.The effect of vegetation on the turbulent burst cycle is mostly obvious up to approximately two-third of vegetation height where this phenomenon is also observed for most other turbulent structure.展开更多
It is widely accepted that urban plant leaves can capture airborne particles. Previous studies on the particle capture capacity of plant leaves have mostly focused on particle mass and/or size distribution. Fewer stud...It is widely accepted that urban plant leaves can capture airborne particles. Previous studies on the particle capture capacity of plant leaves have mostly focused on particle mass and/or size distribution. Fewer studies, however, have examined the particle density, and the size and shape characteristics of particles, which may have important implications for evaluating the particle capture efficiency of plants, and identifying the particle sources. In addition, the role of different vegetation types is as yet unclear. Here, we chose three species of different vegetation types, and firstly applied an object-based classification approach to automatically identify the particles from scanning electron microscope（SEM）micrographs. We then quantified the particle capture efficiency, and the major sources of particles were identified. We found（1） Rosa xanthina Lindl（shrub species） had greater retention efficiency than Broussonetia papyrifera（broadleaf species） and Pinus bungeana Zucc.（coniferous species）, in terms of particle number and particle area cover.（2） 97.9% of the identified particles had diameter ≤10 μm, and 67.1% of them had diameter ≤2.5 μm. 89.8% of the particles had smooth boundaries, with 23.4% of them being nearly spherical.（3） 32.4%–74.1% of the particles were generated from bare soil and construction activities, and 15.5%–23.0% were mainly from vehicle exhaust and cooking fumes.展开更多
文摘This study presents results from a vegetation-induced flow experimental study which investigates 3-D turbulence structure profiles,including Reynolds stress,turbulence intensity and bursting analysis of open channel flow.Different vegetation densities have been built between the adjacent vegetations,and the flow measurements are taken using acoustic Doppler velocimeter(ADV)at the locations within and downstream of the vegetation panel.Three different tests are conducted,where the first test has compact vegetations,while the second and the third tests have open spaces created by one and two empty vegetation slots within the vegetated field.Observation reveals that over 10%of eddies size is generated within the vegetated zone of compact vegetations as compared with the fewer vegetations.Significant turbulence structures variation is also observed at the points in the non-vegetated row.The findings from burst-cycle analysis show that the sweep and outward interaction events are dominant,where they further increase away from the bed.The effect of vegetation on the turbulent burst cycle is mostly obvious up to approximately two-third of vegetation height where this phenomenon is also observed for most other turbulent structure.
基金supported by the “One-Hundred Talents” program of the Chinese Academy of Sciences (No. N234)the National Natural Science Foundation of China(Nos. 41430638 and 41301199)the project “Major Special Project-The China High-Resolution Earth Observation System”
文摘It is widely accepted that urban plant leaves can capture airborne particles. Previous studies on the particle capture capacity of plant leaves have mostly focused on particle mass and/or size distribution. Fewer studies, however, have examined the particle density, and the size and shape characteristics of particles, which may have important implications for evaluating the particle capture efficiency of plants, and identifying the particle sources. In addition, the role of different vegetation types is as yet unclear. Here, we chose three species of different vegetation types, and firstly applied an object-based classification approach to automatically identify the particles from scanning electron microscope（SEM）micrographs. We then quantified the particle capture efficiency, and the major sources of particles were identified. We found（1） Rosa xanthina Lindl（shrub species） had greater retention efficiency than Broussonetia papyrifera（broadleaf species） and Pinus bungeana Zucc.（coniferous species）, in terms of particle number and particle area cover.（2） 97.9% of the identified particles had diameter ≤10 μm, and 67.1% of them had diameter ≤2.5 μm. 89.8% of the particles had smooth boundaries, with 23.4% of them being nearly spherical.（3） 32.4%–74.1% of the particles were generated from bare soil and construction activities, and 15.5%–23.0% were mainly from vehicle exhaust and cooking fumes.
