• Title, Summary, Keyword: deposition velocity

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The Characteristics of the Dry Deposition Velocity for O3 regarding Surface Wetness (지표면 Wetness에 따른 오존의 건성침적속도 특성)

  • 이화운;김유근;문난경
    • Journal of Environmental Science International
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    • v.12 no.4
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    • pp.393-397
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    • 2003
  • It has been researched the relationship between deposition velocity and factors which could affect the deposition phenomena and deposition velocity also has been estimated fer several land-use types. The typical deposition velocities are complex functions of surface types, atmospheric stabilities, friction velocities, air pollutants and so on. The canopy resistance is major contribution to the model's total resistance for O₃. Canopy wetness is also an important factor to calculate deposition velocity. We considered the canopy wetness as canopy water content(CWC) in our Model. But, it is not easy to observe CWC over each land-use types. In this study, we use CWC observed by EMEFS(CANADA Environment Service, 1988) to examine the influence of CWC in estimation of 03 dry deposition velocity(V/sub d/) in summertime. The value of O₃ V/sub d/ range 0.2 ∼ 0.7 cm s/sup -1/ on dry surface and 0.01 ∼ 0.35 cm s/sup -1/ on wet surface in daytime.

Seasonal Variations of $SO_2$Dry Deposition Velocity Obtained by Sonic Anemometer-Thermometer (초음파 풍속온도계를 이용한 $SO_2$건성침착속도의 계절변화 특징)

  • 이종범;박세영
    • Journal of Korean Society for Atmospheric Environment
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    • v.14 no.5
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    • pp.465-478
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    • 1998
  • In this study, seasonal variations of the dry deposition velocity and deposition flux for the sulfur dioxide were analysed. The field observation was performed during one year (from November 1, 1995 to October 31, 1996) in Chunchon basin. The turbulence data were measured by 3-dimensional sonic anemometer/thermometer, and were estimated by mean meteorological data obtained at two heights (2.5 m and 10 m) of meteorological tower. Also, the estimation methods were evaluated by comparing the turbulence data. The results showed that the estimated dry deposition velocity and turbulence parameter such as uc and sensible heat flux using mean meteorological data were relatively similar to the sonic measurements, but all showed somewhat large differences. The dry deposition velocity was large in summer and small in winter mainly due to canopy resistance (rc). The major factor which affects diurnal variation of the velocity was aerodynamic resistance (rw). The SO2 dry deposition flux was large in winter and small in summer in Chunchon.

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Numerical Simulation of Particle Deposition on a Wafer Surface (웨이퍼 표면상의 입자침착에 관한 수치 시뮬레이션)

  • 명현국;박은성
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.9
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    • pp.2315-2328
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    • 1993
  • The turbulence effect of particle deposition on a horizontal free-standing wafer in a vertical flow has been studied numerically by using the low-Reynolds-number k-.epsilon. turbulence model. For both the upper and lower surfaces of the wafer, predictions are made of the averaged particle deposition velocity and its radial distribution. Thus, it is now possible to obtain local information about the particle deposition on a free-standing wafer. The present result indicates that the particle deposition velocity on the lower surface of wafer is comparable to that on the upper one in the diffusion controlled deposition region in which the particle sizes are smaller than $0.1{\mu}m$. And it is found in this region that, compared to the laminar flow case, the averaged deposition velocity under the turbulent flow is about two times higher, and also that the local deposition velocity at the center of wafer is high equivalent to that the wafer edge.

Aerosol Deposition and Behavior on Leaves in Cool-temperate Deciduous Forests. Part 3: Estimation of Fog Deposition onto Cool-temperate Deciduous Forest by the Inferential Method

  • Katata, Genki;Yamaguchi, Takashi;Sato, Haruna;Watanabe, Yoko;Noguchi, Izumi;Hara, Hiroshi;Nagai, Haruyasu
    • Asian Journal of Atmospheric Environment
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    • v.7 no.1
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    • pp.17-24
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    • 2013
  • Fog deposition onto the cool-temperate deciduous forest around Lake Mashu in northern Japan was estimated by the inferential method using the parameterizations of deposition velocity and liquid water content of fog (LWC). Two parameterizations of fog deposition velocity derived from field experiments in Europe and numerical simulations using a detailed multi-layer atmosphere-vegetation-soil model were tested. The empirical function between horizontal visibility (VIS) and LWC was applied to produce hourly LWC as an input data for the inferential method. Weekly mean LWC computed from VIS had a good correlation with LWC sampled by an active string-fog collector. By considering the enhancement of fog deposition due to the edge effect, fog deposition calculated by the inferential method using two parameterizations of deposition velocity agreed with that computed from throughfall data. The results indicated that the inferential method using the current parameterizations of deposition velocity and LWC can provide a rough estimation of water input due to fog deposition onto cool-temperature deciduous forests. Limitations of current parameterizations of deposition velocity related to wind speed, evaporation loss of rain and fog droplets intercepted by tree canopies, and leaf area index were discussed.

Measurement of Particle Deposition Velocity Toward a Vertical Wafer Surface (수직 웨이퍼상의 입자 침착속도의 측정)

  • Bae, G.N.;Lee, C.S.;Park, S.O.;Ahn, K.H.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.7 no.3
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    • pp.521-527
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    • 1995
  • The average particle deposition velocity toward a vertical wafer surface in a vertical airflow chamber was measured by a wafer surface scanner(PMS Model SAS-3600). Polystyrene latex(PSL) spheres with diameters between 0.3 and $0.8{\mu}m$ were used. To examine the effect of the airflow velocity on the deposition velocity, experiments were conducted for three vertical airflow velocities ; 20, 30, 50cm/s. Experimental data of particle deposition velocity were compared with those given by prediction model suggested by Liu and Ahn(1987).

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Nanoparticle deposition in transient gaseous microchannel flow considering hindered motion and rarefaction effect

  • Andarwa, Salahaddin;Tabrizi, Hassan Basirat
    • The Korean Journal of Chemical Engineering
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    • v.34 no.5
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    • pp.1319-1327
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    • 2017
  • Interaction between wall and flow becomes more important when the scale of a channel decreases. We investigated two effects of wall presence for the transport of nanoparticle in a microchannel, which are the rarefaction effect up to early transient regime and hindered motion of nanoparticles. Lattice Boltzmann method coupled with Lagrangian nanoparticle tracking was used for modeling. Series of numerical simulation for various nanoparticle diameters, channel geometries, fluid velocities, and Knudsen numbers were performed. Some important features on nanoparticle transport such as capture efficiency, deposition velocity and deposition location were discussed. Using suitable dimensionless parameters, correlations for capture efficiency and deposition velocity were obtained. Considering hindered motion leads to significant decrease in the capture efficiency and deposition velocity. Results show that the effect of rarefaction on deposition is mostly because of varying the force acting on nanoparticles not due to slip velocity of fluid field near boundaries.

Measurement of Dry Deposition of Polycyclic Aromatic Hydrocarbons in Jeoniu (전주지역에서 다환방향족 탄화수소의 건식 침적 측정)

  • Kim, Hyoung-Seop;Kim, Jong-Guk;Ghim, Young-Sung
    • Journal of Korean Society for Atmospheric Environment
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    • v.23 no.2
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    • pp.242-249
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    • 2007
  • Deposition fluxes of polycyclic aromatic hydrocarbons (PAHs) were measured at the Chonbuk National University located in Jeonju between June and November 2002. Fluxes of gaseous and particulate PAHs were separately obtained using a water surface sampler (WSS) and a dry deposition plate (DDP). Most of PAHs were deposited in the gaseous form since the low molecular weight PAHs dominates in the atmosphere. The deposition velocity of particulate PAHs was higher than that of gaseous PAHs when the molecular weight was low, but substantially decreased as the fine particle fraction increased with molecular weight. The deposition velocity was generally higher at high wind speeds. However, increase in the deposition velocity in unstable atmospheric conditions was also observed for gaseous PAHs of intermediate molecular weight.

Transport and Deposition Characteristics of Coarse Grained Soil According to the Flow Velocity and Grain Size (유속 및 입경에 따른 조립토의 이동 및 퇴적 특성)

  • Bong, Tae-Ho;Son, Young-Hwan;Kim, Kyu-Sun;Park, Jae-Sung;Kim, Dong-Geun
    • Journal of The Korean Society of Agricultural Engineers
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    • v.58 no.1
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    • pp.11-17
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    • 2016
  • Dredging and land reclamation works has actively carried out for the efficient use of land and secure of agricultural and industrial site. During the reclamation, a portion of landfills are lost from the desired location due to a variety of causes. However, these causes has been rarely studied, and water flow velocity has a great influence on the movement of landfills. For the economical and efficient reclamation, it is important to predict the movement of landfills in water. In this paper, an experimental study was carried out to investigate the deposition distance according to the flow velocity and soil grain size. We have made a large open-channel apparatus that can reproduce a laminar flow, and the deposition test was carried out on the four grain size (0.638, 1.425, 3.375, 7.125 mm) and four flow velocity (0.1, 0.3, 0.5, 0.67 m/s) with high definition video recording. As a results, average deposition distance increased with the flow velocity, and its relationship is shown linearly. For the grain size, the average deposition distance were drastically increased as the grain size becomes smaller.

Particle deposition on a rotating disk in application to vapor deposition process (VAD) (VAD공정 관련 회전하는 원판으로의 입자 부착)

  • Song, Chang-Geol;Hwang, Jeong-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.1
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    • pp.61-69
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    • 1998
  • Vapor Axial Deposition (VAD), one of optical fiber preform fabrication processes, is performed by deposition of submicron-size silica particles that are synthesized by combustion of raw chemical materials. In this study, flow field is assumed to be a forced uniform flow perpendicularly impinging on a rotating disk. Similarity solutions obtained in our previous study are utilized to solve the particle transport equation. The particles are approximated to be in a polydisperse state that satisfies a lognormal size distribution. A moment model is used in order to predict distributions of particle number density and size simultaneously. Deposition of the particles on the disk is examined considering convection, Brownian diffusion, thermophoresis, and coagulation with variations of the forced flow velocity and the disk rotating velocity. The deposition rate and the efficiency directly increase as the flow velocity increases, resulting from that the increase of the forced flow velocity causes thinner thermal and diffusion boundary layer thicknesses and thus causes the increase of thermophoretic drift and Brownian diffusion of the particles toward the disk. However, the increase of the disk rotating speed does not result in the direct increase of the deposition rate and the deposition efficiency. Slower flow velocity causes extension of the time scale for coagulation and thus yields larger mean particle size and its geometric standard deviation at the deposition surface. In the case of coagulation starting farther from the deposition surface, coagulation effects increases, resulting in the increase of the particle size and the decrease of the deposition rate at the surface.

Analysis on Particle Deposition on a Heated Rotating Disk (가열되는 회전원판으로의 입자 침착 해석)

  • Yu, Gyeong-Hun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.2
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    • pp.245-252
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    • 2002
  • Numerical analysis was conducted to characterize particle deposition on a horizontal rotating disk with thermophorectic effect under laminar flow field. The particle transport mechanisms considered were convection, Brownian diffusion, gravitational settling and thermophoresis. The averaged particle deposition velocities and their radial distributions for the upper surface of the disk were calculated from the particle concentration equation in a Eulerian frame of reference for rotating speeds of 0∼1000rpm and temperature differences of 0∼5K. It was observed from the numerical results that the rotation effect of disk increased the averaged deposition velocities, and enhanced the uniformity of local deposition velocities on the upper surface compared with those of the disk at rest. It was also shown that the heating of the disk with ΔT=5K decreased deposition velocity over a fairly broad range of particle sizes. Finally, an approximate deposition velocity model for the rotating disk was suggested. The comparison of the present numerical results with the results of the approximate model and the available experimental results showed relatively good agreement between them.