• 대한기계학회논문집
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• 제17권7호
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• pp.1794-1804
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• 1993

The thermal stress intensity factors for interface cracks of Griffith and symmetric lip cusp types under vertical uniform heat flow in a finite body are calculated by boundary element method. The boundary conditions on the crack surfaces are insulated or fixed to constant temperature. The relationship between the stress intensity factors and the displacements on the nodal point of a crack tip element is derived. The numerical values of the thermal stress intensity factors for interface Griffith crack in an infinite body and for symmetric lip cusp crack in a finite and homogeneous body are compared with the previous solutions. The thermal stress intensity factors for symmetric lip cusp interface crack in a finite body are calculated with respect to various effective crack lengths, configuration parameters, material property ratios and the thermal boundary conditions on the crack surfaces. Under the same outer boundary conditions, there are no appreciable differences in the distribution of thermal stress intensity factors with respect to each material properties. But the effect of crack surface thermal boundary conditions on the thermal stress intensity factors is considerable.

• KIEAE Journal
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• 제7권2호
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• pp.17-23
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• 2007

While heat island has been recognized as an unique environmental nuisance in cities, the phenomenon tends to be regarded as an inevitable side effect on urbanization. Recently the nature of the heat island has been disclosed and efforts for the remedy have been discussed in many ways. Some pioneering actions have been taken to mitigate the strength of the heat island's intensity in several countries. After studies for the heat island and speculations on current pilot policies of 3 different countries has been done, mitigation policies for heat island has been suggested as followings. 1. Preservation of natural topography is essential because latent energy consumption(evapotranspiration) from the site is the single most important factor to mitigate the energy surplus caused by urban heat island. 2. Because current national zoning ordinance or building law can not effectively control the site specific local environment, heat island policy should be established or employed at local level. 3. Incentives for the mitigation should be adopted on the process of implementation because environment is public concern. 4. Wind can easily dissipate energy surplus which is the major driving force for heat island. Therefore local wind, the direction and intensity should be sustained and sometimes facilitated fully through policies.

• 한국지리정보학회지
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• 제15권1호
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• pp.133-143
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• 2012

본 연구는 창원시 도시지역을 대상으로 도시공간을 고려한 야간시간대의 도시열섬특성을 파악하기 위해 1:1,000 축척의 토지이용도 및 토지피복도와 DTM, 그리고 ASTER 위성영상에서 추출된 야간시간대의 지표온도자료를 활용하였다. 분석결과에 따르면, 야간시간대는 건물이 밀집되어있는 단독주거지역이 상업지역이나 공공시설지역보다 열섬강도가 높았고, 이것은 에너지소비에 의한 인공열 방출이 열섬형성에 많은 영향을 미치기 때문으로 판단된다. 또한 이러한 점 때문에 공업지역에서는 건물은 가동시간에 따라 온도차이가 매우 크게 나타났다. 한편, 도시녹지지역과 하천지역은 도시열섬을 완화하는 냉각효과가 있는 것으로 확인되었으며, 열섬강도가 높은 지역에 녹지 및 수변공간의 조성으로 열섬강도를 낮출 필요가 있을 것으로 판단된다. 이상과 같은 결과는 야간시간대의 도시열섬을 완화하는데 있어 개발계획 수립시 효율적인 공간활용을 위해 기초자료로 이용될 것으로 사료된다.

• 대기
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• 제31권2호
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• pp.143-156
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• 2021

This study investigates the impacts of land cover change due to urbanization on the Urban Heat Island Intensity (UHII) and the Heat Index (HI) over the Seoul metropolitan area using the Unified Model (UM) with the Met Office Reading Urban Surface Exchange Scheme (MORUSES) during the heat wave from 16, July to 5, August 2018. Two simulations are performed with the late 1980s land-use (EXP1980) and the late 2000s land-use (EXP2000). EXP2000 is verified using Automatic Weather Station (AWS) data from 85 points in the study area, and observation sites are classified into two categories according to the urban fraction change over 20 years; Category A is 0.2 or less increase, and Category B is 0.2 or more increase. The 1.5-m temperature and relative humidity in Category B increase by up to 1.1℃ and decreased by 7% at 1900 LST and 2000 LST, respectively. This means that the effect of the urban fraction changes is higher at night. UHII increases by up to 0.3℃ in Category A and 1.3℃ in Category B at 1900 LST. Analysis of the surface energy balance shows that the heat store for a short time during the daytime and release at nighttime with upward sensible heat flux. As a result of the HI, there is no significant difference between the two experiments during the daytime, but it increases 1.6℃ in category B during the nighttime (2200 LST). The results indicate that the urbanization increase both UHII, and HI, but the times of maximum difference between EXP1980 and EXP2000 are different.

• 대한기계학회논문집
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• 제16권7호
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• pp.1255-1265
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• 1992

본 연구에서는 단열 및 온도가 영으로 고정된 경계조건을 갖는 대칭 입술형과 대칭 익형 강체함유 물상의 접합경계면 균열에 대한 Hilbert 문제로부터 복소 포텐셜 함수와 커스프 균열선단 그리고 접합경계면 균열선단에서 TSIF를 구하고자 한다.

• 대기
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• 제23권4호
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• pp.413-424
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• 2013

Urban Heat Island (UHI) intensity is one of vital parameters in studying urban boundary layer meteorology as well as urban planning. Because the UHI intensity is defined as air temperature difference between urban and rural sites, an objective sites selection criterion is necessary for proper quantification of the spatial variations of the UHI intensity. This study quantified the UHI intensity and its spatial pattern, and then analyzed their connections with urban structure and metabolism in Seoul metropolitan area where many kinds of land use and land cover types coexist. In this study, screen-level temperature data in non-precipitation day conditions observed from 29 automatic weather stations (AWS) in Seoul were analyzed to delineate the characteristics of UHI. For quality control of the data, gap test, limit test, and step test based on guideline of World Meteorological Organization were conducted. After classifying all stations by their own local climatological properties, UHI intensity and diurnal temperature range (DTR) are calculated, and then their seasonal patterns are discussed. Maximum UHI intensity was $4.3^{\circ}C$ in autumn and minimum was $3.6^{\circ}C$ in spring. Maximum DTR appeared in autumn as $3.8^{\circ}C$, but minimum was $2.3^{\circ}C$ in summer. UHI intensity and DTR showed large variations with different local climate zones. Despite limited information on accuracy and exposure errors of the automatic weather stations, the observed data from AWS network represented theoretical UHI intensities with difference local climate zone in Seoul.

• 한국대기환경학회지
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• 제7권1호
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• pp.49-53
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• 1991

Relations of urban heat island and air pollution are analyzed by using $SO_2$ concentration data (winter season in 1985) from 10 sites of Seoul area and differences of wind speed and air temperature in urban and rural area. Urban heat island is developed when daily mean wind speed at urban site is lower than 1.5m/sec or in the interval of 3.0 $\sim$ 3.5m/sec. When differences between urban and rural air temperature is greater than the overall average of those differences, $SO_2$ concentrations of those above-average differences are 1.3 $\sim$ 1.8 times higher than those of below-average differences. The trends are shown obviously at north-eastern area of Seoul (Gilum Dong, Ssangmun Dong, Myeonmog Dong). When intensity of Urban Heat Island is weak, $SO_2$ concentration was reduced in propotion to a rise of wind speed. But $SO_2$ concentration is on the partial increase in spite of a rise of wind speed when intensity of urban heat island is strong.

• 대기
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• 제18권4호
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• pp.355-365
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• 2008

Synoptic and climatological characteristics of heat waves over Korea and Europe as well as their biometeorological impacts were compared. In July of 1994, excess deaths of about 2,388 in the population of South Korea are estimated by the modified excess death calculation algorithm ofKysely (2004). The excess deaths correspond to the net mortality increase of 12.5% in July of 1994 if we compare the estimated value to the expected number of deaths in this month (i.e., about 19,171). The comparative study of heat waves in Korea and Europe shows that the record-breaking heat waves in both regions are closely associated with prolonged droughts. In particular, reduction of soil moisture, precipitation and cloud cover and enhancement of insolation during the drought periods are very likely to be related to the increase in the intensity and the duration ofheat waves. Climate models predict that the frequency, intensity, and duration of heat waves in the 21 st century will be greatly enhanced in both areas. In order to reduce the biometeorological and socioeconomic impacts due to heat waves, not only the development of heat-related mortality prediction model that can be widely applied to many climate regimes, but also studies on the climatological association between extreme temperatures and abnormal hydrological cycle are needed.

• 설비공학논문집
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• 제11권6호
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• pp.855-860
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• 1999

An experimental study of jet impingement on the surface with linear temperature gradient is conducted with the presentation of the turbulent characteristics and the heat transfer rates measured when this jet impinges normally to a flat plate. The jet Reynolds number ranges from 30,000 to 90,000, the temperature gradient of the plate is 2~$4.2^{\circ}C$/cm and the dimensionless nozzle to plate distance(H/D) is from 6 to 10. The results show that the peak of heat transfer rate occurs at the stagnation point, and the heat transfer rate decreases as the radial distance from the stagnation point increases. A remarkable feature of the heat transfer rate is the existence of the second peak. This is due to the turbulent development of the wall jet. Maximum heat transfer rate occurs when the axial distance from the nozzle to nozzle diameter(H/D) is 8. The heat transfer rate can be correlated as a power function of Prandtl number, Reynolds number and the dimensionless nozzle to plate distance(H/D). It has been found that the heat transfer rate increases with increasing turbulent intensity.

• 설비공학논문집
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• 제3권3호
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• pp.186-196
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• 1991

Numerical analysis has been performed to investigate the effects of the turbulence intensity and Prandtl number on the local heat transfer around a circular cylinder in crossflow. The governing equations were reformulated in a non-orthogonal coordinate system with Cartesian velocity components and discretised by the finite volume method with a non-staggered variable arrangement. For laminar flow, the calculations were performed for the Reynolds numbers 26 and 200. The results showed good agreement with the experimental results. For turbulent flow of the Reynolds number $1{\times}10^5$ and $2{\times}10^6$, the results showed that with an increase in the turbulent intensity in the main stream, the local Nusselt number increases in the front region of the circular cylinder. But the effect of turbulent intensity on the local Nusselt number diminishes in the wake region. The influence of Prandtl numbers show similar trend to that of turbulent intensity.