• Journal of the Korean Society of Environmental Restoration Technology
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• v.12 no.2
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• pp.73-82
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• 2009

The traffic volume of Seoul is extremely high in comparison to other major cities in Korea, and the result has been harmful physical and mental exposure to pollution by Seoulites on a regular basis. The street air pollution is more important than the others, because the air pollution generated by street traffic directly impacts the health of nearby pedestrians. This problem requires urgent attention and resolution. Among the factors creating the air pollution originating from the street, is the configuration of streets, which have emerged as the most significant because it is related to air and pollutant dispersion. Therefore, this study was conducted under the assumption that street form affects the air quality. Study sites were classified by street characteristics, and air quality was analyzed in each class. Then the OSPM (Operational Street Pollution Model) was employed to simulate the relationship between street configuration and air quality of streets within the old city center and new city center in Seoul. After that this study analyzed the correlation between air pollution and the spatial configuration of urban streets (ex. street width, building height, building density, etc.) to determine their contributions to air pollution. The outcome of this study is as follows : First, the result that was derived from the correlation analysis between street configuration and air quality hewed that the air pollution of the street is influenced by the average height of building, width of the roads as well as traffic volume. On the roadside, the concentration level of $NO_2$ is mainly affected by the average height of building and the deviation of building height along the street and CO is affected by street width. The outcome of this study can be used as a basis for more sound urban design policies, and the promotion of desirable street environments for pedestrians.

• Journal of the Korean housing association
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• v.14 no.3
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• pp.29-40
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• 2003

Street-in-the-air has been regarded as a device which supplements the defects of high-rise blocks. It should be, however, noted that most of street-in-the-air has been based on the concept of urbanity in the automobile era as well. Based on this point of view, the 5 types of approaches to the street-in-the-air in this paper were introduced. Throughout the research, it was figured out that the types of approaches focusing the urban spatial system tended to neglect the essential properties of street itself as place for everyday life. In considering that street is defined by relationship with building or units, it is necessary to secure the correlation of street-in-the-air with units prior to considering the urban spatial system.

• Atmosphere
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• v.24 no.3
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• pp.331-341
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• 2014

In this study, the effects of building-roof cooling on scalar dispersion in three-dimensional street canyons are investigated using a computational fluid dynamics (CFD) model. For this, surface temperature of building roof is systematically changed and non-reactive pollutants are released from street bottom in urban street canyons with the aspect ratio of 1. The characteristics of flow, air temperature, and non-reactive pollutant dispersion in the control experiment are analyzed first. Then, the effects of building-roof cooling are investigated by comparing the results with those in the control experiment. In the control experiment, a portal vortex which is a secondary flow induced by ambient air flow is formed in each street canyon. Averaged air temperature is higher inside the street canyon than in both sides of the street canyon, because warmer air is coming into the street canyon from the roof level. However, air temperature near the street bottom is lower inside the street canyon due to the inflow of cooler air from both sides of the street canyon. As building-roof temperature decreases, wind speed at the roof level increases and portal vortex becomes intensified (that is, downdraft, reverse flow, and updraft becomes stronger). Building-roof cooling contributes to the reduction of average concentration of the non-reactive pollutants and average air temperature in the street canyon. The results imply that building-roof cooling has positive effects on improvement of thermal environment and air quality in urban areas.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.852-858
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• 2005

Modeling techniques for air quality are useful tools in air quality management. Especially, the air quality in urban area is significantly influenced by local surroundings such as buildings and traffic. When considering the air quality in a street canyon, which is usually filmed by a series of consecutive buildings and a street, currently available air dispersion model have a number of limitations to predict the air quality properly. In this study, it is aimed to propose an empirical model for the air quality in urban street canyons. A series of wind tunnel tests, followed by statistical analysis, were conducted. In conclusion, it is found that a wide street canyon and a perpendicular external wind to the street canyon are beneficial to achieve an enhanced air quality in street canyon environment. The model prediction using the proposed model also shows reliable correlations to the wind tunnel test results.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.3
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• pp.281-289
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• 1999

A new E-$\varepsilon$ turbulence numerical model is proposed for analysing the turbulent air flow field within are urban street canyon. In this model the equations of eddy viscosity and energy dissipation ae reformed by considering the Kolmogorov time scale and streamline curvature effect. Application results of the new E-$\varepsilon$ model have been compared with those of standard E-$\varepsilon$ model and Yang and Shih's one, which are commonly used ones in engineering fields, and with field experiment results of DePaul and Sheih. The new model appears to be generally superior to other both models in the prediction of an air flow field within street canyon.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.04a
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• pp.176-177
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• 2000

대도시의 국소지역인 도심지 도로변 양측은 빌딩에 의해 둘러싸여 있어 canyon으로 비유되어 street canyon이라고 하며 도로에 관한 선행연구는 도로변에 관한 것과 street canyon에 관한 것 그리고 두 경우를 전부 포함하는 경우로 분류할 수 있다. 도로변에 있어서 자동차 배출가스의 확산 예측에 관한 연구는 가우시안형 해석해 모형이 가장 많고 그 외 비가우시안형 해석해 모형, 반경험식 모형, 수치해 모형으로 분류되고 있다. (중략)

• Asian Journal of Atmospheric Environment
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• v.10 no.4
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• pp.179-189
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• 2016

Here we evaluated the effect of using water retentive pavement or WRP made from fly ash as material for main street in a real city block. We coupled computational fluid dynamics and pavement transport (CFD-PT) model to examine energy balance in the building canopies and ground surface. Two cases of 24 h unsteady analysis were simulated: case 1 where asphalt was used as the pavement material of all ground surfaces and case 2 where WRP was used as main street material. We aim to (1) predict diurnal variation in air temperature, wind speed, ground surface temperature and water content; and (2) compare ground surface energy fluxes. Using the coupled CFD-PT model it was proven that WRP as pavement material for main street can cause a decrease in ground surface temperature. The most significant decrease occurred at 1200 JST when solar radiation was most intense, surface temperature decreased by $13.8^{\circ}C$. This surface temperature decrease also led to cooling of air temperature at 1.5 m above street surface. During this time, air temperature in case 2 decreased by $0.28^{\circ}C$. As the radiation weakens from 1600 JST to 2000 JST, evaporative cooling had also been minimal. Shadow effect, higher albedo and lower thermal conductivity of WRP also contributed to surface temperature decrease. The cooling of ground surface eventually led to air temperature decrease. The degree of air temperature decrease was proportional to the surface temperature decrease. In terms of energy balance, WRP caused a maximum increase in latent heat flux by up to $255W/m^2$ and a decrease in sensible heat flux by up to $465W/m^2$.

• Atmosphere
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• v.26 no.3
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• pp.423-433
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• 2016

In this study, performance of a computational fluid dynamics (CFD) model is assessed from analysis on air flow pattern which is observed in the artificial street canyon. Field observations focusing on flows were conducted at an artificial street canyon in Magok region. For the observation of three-dimensional airflow structures, twelve three-dimensional wind anemometers (hereafter, CSAT3) were installed inside the street canyon. The street canyon was composed of two rectangular buildings with 35-m length, 4-m width, and 7-m height. The street width (distance between the buildings) is 7 m, making the street aspect ratio (defined by the ratio of building height to street width) of 1. For the observation of above-building wind, a CSAT3 was installed above the northwest-side building. Southwesterly, westerly and northwesterly were dominant in the street canyon during the observations. Because wind direction is parallel to the street canyon in the southwesterly case, westerly and northwesterly were selected as inflow directions in numerical simulations using a computational fluid dynamics model developed through the collaborative research project between National Institute of Meteorological Sciences and Seoul National University (CFD_NIMR_SNU). The observations showed that a well-structured vortex flow (skimming flow) and an evidence of a small eddy at the corner of the downwind building and ground appeared. The CFD_NIMR_SNU reproduced both the observed flow patterns reasonably well, although wind speeds inside the street canyon were underestimated.

• Korean Journal of Agricultural and Forest Meteorology
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• v.6 no.1
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• pp.24-29
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• 2004

The purpose of this study was to identify the effects of air pollution on the street trees in Seoul. Ten Gingko biloba street trees were selected in both Jongno(polluted area as a control) and Yangjae(non-polluted area) to investigate chlorophyll contents, photosynthesis and antioxidant enzymes such as APX(Ascorbate peroxidase) and GR(Glutathione reductase). The sampling, measurements and analysis were conducted in August. Chlorophyll contents and photosynthesis of Gingko biloba grown in Yangjae were higher than those of Jongno in the August measurement. In contrast, APX and GR activities of Gingko biloba grown in Yangjae were lower than those of Jongno. The observed tree responses are considered to be atypical compensatory response to polluted locations.

• International Journal of High-Rise Buildings
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• v.2 no.2
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• pp.115-121
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• 2013

The ventilation performance of a street in Bangkok, Thailand, was investigated by performing measurements and conducting a CFD analysis. We focused on a street that was covered by an elevated train station. It was shown that the ventilation efficiency varied drastically depending on the angle between the street and the wind direction. When the wind direction was parallel to the street, the elevated structure had a negative influence, which created higher pollutant concentrations than in locations without elevated structures. However, when the wind direction was perpendicular to the street, the pollutant concentrations in the two situations were similar. Using a CFD analysis and ventilation performance indexes, it was shown that the elevated structure directed the wind flow and enhanced the ventilation efficiency, which positively affected ventilation performance. These kinds of knowledge can lead us to optimize city planning including high-rise buildings with high ventilation efficiency.