표면조도의 영역밀도가 경계층에 미치는 영향
Effect of Area Density of Surface Roughness on Turbulent Boundary Layer
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초록
대기경계층은 지표면의 각종 거칠기에 의해 생성되는 경계층으로 여러 층으로 나누어진다. 그 중 특히 조도부분층 (RoughnessSub-layer, RS)는 대기경계층에서 가장 낮은 부분에 존재하는 층으로 지표면의 영향을 직접적으로 받아 강한 난류유동이 발생되는 층이다. 이로 인해 경계층 내에 있는 어러 건축물 및 구조물들은 난류유동에 의한 풍하중과 같은 여러 문제에 직면하고 있다. 따라서 이대기경계층 내의 유동특성을 파악하는 것은 매우 중요하다. 이에 본 논문에서는 표면조도를 두 가지 패턴 (staggered and aligned pattern)과 세 가지 영역밀도 (25%, 17%, 11%)에 따라 구분하고 배치하여 경계층 내 유동을 측정하였다. 그 결과, 속도분포가 영역밀도에 따라 값 분포 차이를 보였으며, 특히 조도부분층 높이는 영역밀도가 낮아짐에 따라 그 높이가 높아졌다 (1.8H-2.2H). 따라서 영역밀도가경계층 내 유동에 상당한 영향을 준다는 것을 확인하였고, 패턴의 변화는 큰 영향이 없다는 것을 확인하였다. 영역밀도는 표면압력에도 영향을 주었다. 모델 앞면의 표면압력은 영역밀도가 높아짐에 따라 그 값이 작아졌다.
Abstract
This study quantitatively assesses the risk of wind damage to building cladding by predicting future changes in wind speeds caused by climate change in South Korea. In order to predict changes in wind speed due to future climate change, the results of a previous study that predicted changes in the wind speed in South Korea using the HadGem3-RA model and the RCP scenarios provided by the Korea Meteorological Administration were utilized. The wind risk was then assessed using a convolution of the wind fragility model, representing the probability of failure due to an arbitrary wind speed, and the wind hazard model, representing the probability of occurrence of strong wind speed. The wind fragility model was developed using a Monte-Carlo simulation, while the wind hazard model was taken from a previous study that analyzed the probability of occurrence of typhoon-induced strong wind speeds around South Korea using past typhoon historical data and the Monte-Carlo simulation method. Based on the results of the wind risk assessment, the changes in wind risk due to future changes in wind speed were quantitatively compared. From the results, the high wind speeds occur more in the southern region of South Korea where typhoons mostly pass, than they do Seoul. In additionally, there is no change in the wind risk for Busan because the changes in the wind speed are insignificant under both RCP 4.5 and RCP 8.5. The methodology of this study can be used as a basis for predicting and preparing for future wind-induced damage. It is necessary to expand the target structures for wind fragility assessment as well as the assessment areas of the wind hazard to evaluate wind risk for the national level.
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