• 대기
• /
• 제24권3호
• /
• pp.331-341
• /
• 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.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2013년도 제46회 KOSCO SYMPOSIUM 초록집
• /
• pp.123-126
• /
• 2013

Combustor development requires high fidelity simulation capable of predicting recirculation zone (RZ), temperature field, and pollutant emission. Swirling flow is widely used in combustor for its benefits in efficient mixing and flame stabilization by RZ. Large eddy simulation (LES) is used to calculate swirling flow in an expanding pipe [1], and shows higher accuracy than RANS. Reactive flow modeling using LES and flamelet model is validated with experiments by Barlow et al. [4] and Masri et al. [3]. Finally, heat transfer simulation of Samsung Techwin's combustor liner is presented.

• 한국대기환경학회지
• /
• 제19권3호
• /
• pp.249-261
• /
• 2003

A three-dimensional mesoscale atmospheric dispersion modeling system consisting of the Lagrangian particle dispersion model (LPDM) and the meteorological mesoscale model (MM5) was employed to simulate the transport and dispersion of non-reactive pollutant during the nuclear spill event occurred from Sep. 31 to Oct. 3, 1999 in Tokaimura city, Japan. For the comparative analysis of numerical experiment, two more sets of foreign mesoscale modeling system; NCEP (National Centers for Environmental Prediction) and DWD (Deutscher Wetter Dienst) were also applied to address the applicability of air pollution dispersion predictions. We noticed that the simulated results of horizontal wind direction and wind velocity from three meteorological modeling showed remarkably different spatial variations, mainly due to the different horizontal resolutions. How-ever, the dispersion process by LPDM was well characterized by meteorological wind fields, and the time-dependent dilution factors ($\chi$/Q) were found to be qualitatively simulated in accordance with each mesocale meteorogical wind field, suggesting that LPDM has the potential for the use of the real time control at optimization of the urban air pollution provided detailed meteorological wind fields. This paper mainly pertains to the mesoscale modeling approaches, but the results imply that the resolution of meteorological model and the implementation of the relevant scale of air quality model lead to better prediction capabilities in local or urban scale air pollution modeling.

• 한국환경과학회지
• /
• 제15권5호
• /
• pp.387-396
• /
• 2006

The numerical modeling and comparison with observations are performed to find out the detailed structure of meteorology and the characteristic of related dispersion phenomena of the non-reactive air pollutant at Kyoungin region, South Korea, where several industrial complex including Siwha, Banwol and Namdong is located. MM5 (Fifth Generation NCAR/Penn State Mesoscale Model), 3-D Land/sea breeze model and 3-D diagnostic meteorological model have been utilized for the meteorological simulation for September, 2002 with each different spatial resolution, while 3-D Eulerian air dispersion model for the air quality study. We can see the simulated wind field shows the very local circulation quitely well compared with in-site observations in shoreline area with complex terrains, at which the circulation of Land/sea breeze has developed and merged with the mountain and valley breeze eventually. Also it is shown in the result of the dispersion model that the diurnal variation and absolute value of daily mean $SO_2$ concentrations have good agreement with observations, even though the instant concentration of $SO_2$ simulated overestimates around 1.5 times rather than that of observation due to neglecting the deposition process and roughly estimated emission rate. This results may indicate that it is important for the air quality study at shoreline region with the complex terrain to implement the high resolution meteorological model which is able to handle with the complicate local circulation.