• 대기
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• 제26권3호
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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.

• Wind and Structures
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• 제11권4호
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• pp.275-289
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• 2008

Large eddy simulations have been performed within and over different types of urban building arrays. This paper adopted three dimensionless parameters, building frontal area density (${\lambda}_f$) the variation degree of building height (${\sigma}_h$), and the staggered degree of building range ($r_s$), to study the systematic influence of building spacing, height and layout on wind and turbulent characteristics. The following results have been achieved: (1) As ${\lambda}_f$ decrease from 0.25 to 0.18, the mean flow patterns transfer from "skimming" flow to "wake interference" flow, and as ${\lambda}_f$ decrease from 0.06 to 0.04, the mean flow patterns transfer from "wake interference" flow to "isolated roughness" flow. With increasing ${\lambda}_f$, wind velocity within arrays increases, and the vortexes in front of low buildings would break, even disappear, whereas the vortexes in front of tall buildings would strengthen and expand. Tall buildings have greater disturbance on wind than low buildings do. (2) All the wind velocity profiles and the upstream profile converge at the height of 2.5H approximately. The decay of wind velocity within the building canopy was in positive correlation with ${\lambda}_f$ and $r_s$. If the height of building arrays is variable, Macdonald's wind velocity model should be modified through introducing ${\sigma}_h$, because wind velocity decreases at the upper layers of the canopy and increases at the lower layers of the canopy. (3) The maximum of turbulence kinetic energy (TKE) always locates at 1.2 times as high as the buildings. TKE within the canopy decreases with increasing ${\lambda}_f$ and $r_s$ but the maximum of TKE are very close though ${\sigma}_h$ varies. (4) Wind velocity profile follows the logarithmic law approximately above the building canopy. The Zero-plane displacement $z_d$ heighten with increasing ${\lambda}_f$, whereas the maximum of and Roughness length $z_0$ occurs when ${\lambda}_f$ is about 0.14. $z_d$ and $z_0$ heighten linearly with ${\sigma}_h$ and $r_s$, If ${\sigma}_h$ is large enough, $z_d$ may become higher than the average height of buildings.

• 한국어류학회지
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• 제32권3호
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• pp.182-190
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• 2020

멸종위기어류 가는돌고기 Pseudopungtungia tenuicorpa 복원사업의 일환으로, 2011~2012년 한강의 조종천에 가는돌고기가 방류되었다. 이후 2014부터 2016년까지 방류지에서 가는돌고기가 채집되지 않아 복원사업은 실패한 것으로 평가되었다. 본 연구는 가는돌고기 복원사업이 정말 실패하였는가를 검증하기 위해 2017년부터 2019년까지 정밀조사를 실시하였다. 조사지점은 방류지점을 포함하여 6개 지점을 선정하였으며, 족대와 투망, 일각망, 스쿠버다이빙 등을 이용하여 어류를 채집하였다. 조사결과 방류지점을 포함한 약 0.5 km 구간에서 13개체가 채집되었다. 가는돌고기 서식지역은 수심 0.5~2 m의 큰돌과 암반으로 이루어진 느린 여울부였다. 채집된 가는 돌고기의 연령은 당년생(0+)부터 3년생 이상으로 구성되어 있었으며, 지속적으로 세대교번이 일어나고 있었다. 따라서 조종천에 재도입된 가는돌고기는 비록 많은 개체가 서식하지 않았으나 서식지에 정착하여 지속적으로 세대교번을 하고 있어, 가는돌고기 복원사업은 부분성공으로 평가되었다.