http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
야외 환경에 노출된 입체 구조물에 대한 열적외선 신호 예측 소프트웨어 개발 및 실험적 검증 연구
김동건(D.G. Kim),권구용(K.Y. Kwon),장현성(H.S. Jang),연윤모(Y.M. Yeon),하남구(N.K. Ha) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.3
This paper contains experimental validation of surface temperature and IR(infrared) signal prediction performance for a 3D object placed in an outdoor environment as part of a software development process to predict thermal infrared signals based on computational thermal analysis with considering 3D thermal conduction and unsteady state. For experimental validation, CUBI targets, which are introduced as major verification cases abroad, were produced and installed on the experimental site. Also, thermocouple wires, infrared cameras, a solar tracker and a weather station were installed on the experimental site. Performance validation was carried out step by step, and as the first step, the suitability of the algorithm applied to the developed software was determined through comparison and analysis of prediction results for surface temperature. As a second step, the self-emitted radiance calculation result and the solar and sky reflected radiance calculation algorithm were validated through the analysis of the prediction result for infrared signals. In addition, by assigning the same input conditions to the other commercial software with similar concepts and comparing the calculated results together, the limitations of modeling inevitably appear in the comparison between modeling and measurement were considered. As a result of the validation, it is judged that the thermal infrared signal prediction performance of the software developed through this study is applicable to stereoscopic objects placed in an outdoor environment. In the future, it is necessary to prepare to become software with higher reliability through performance validation of 3D objects that have more complex forms or contain heat sources.
김동건 ( D . K . Kim,T . H . Sanders ) 한국주조공학회 1987 한국주조공학회지 Vol.7 No.3
Commercial semicontinuous cast ingots of aluminum alloys often exhibit large grains composed of parallel arrays of continuous lamellae. Each lamella consists of a central {III} coherent twin boundary and wavy solidification boundary. This microstructure is referred to as a twin columnar growth(TCG) structure. The factors influencing the formation of a TCG structure include a unidirectional thermal gradient and the critical range of the alloying element content. The higher the thermal gradient is, the shorter the twin plane spacings are. The composition profile for an untwinned dendrite shows maximums at the positions of the interdendritic channels and the minimum appears at the center of the dendrite. While for twinned dendrite, it has wavy apperance. This profile has two local minimums instead of one shown in the untwinned.
모델 단순화에 의한 CFRP 복합 구조물의 유효 열전도율 추출 방법 연구
김동건(D.G. Kim),한국일(K.I. Han),최준혁(J.H. Choi),이장준(J.J. Lee),김태국(T.K. Kim) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.4
The thermal balance test in vacuum chamber for satellite structures is an essential step in the process of satellite development. However, it is technically and economically difficult to fully replicate the space environment by using the vacuum chamber. To overcome these limitations, the thermal analysis through a computer simulation technique has been conducted. The CFRP composite material has attracted attention as satellite structures since it has advantages of excellent mechanical properties and light weight. However, the nonuniform nature of the thermal conductivity of the CFRP structure should be noted at the step of thermal analysis of the satellite. Two different approaches are studied for the thermal analyses; a detailed numerical modeling and a simplified model expressed by an effective thermal conductivity. In this paper, the effective thermal conductivities of the CFRP composite structures are extracted from the detailed numerical results to provide a practical thermal design data for the satellite fabricated with the CFRP composite structure. Calculation results of the surface temperature and the thermal conductivities along x, y, z directions show fairly good agreements between the detailed modeling and the simplified model for all the cases studied here.
격자 세분화 방법을 고려한 복사열전달 형상계수 계산 기법 연구
김동건(D.G. Kim),한국일(K.I. Han),최준혁(J.H. Choi),이장준(J.J. Lee),김태국(T.K. Kim) 한국전산유체공학회 2014 한국전산유체공학회지 Vol.19 No.1
Since experiments on the actual operational status are said to be very impractical because of their economic and repeatability problems, it is difficult to understand the thermal profiles of aerospace or military equipments. Thus, the CFD codes with considering the radiation heat transfer are used to compensate the defect. In case, analyzing the radiation exchanges between the object surfaces are very important. Because the temperature and the IR signal distributions of the object surface are significantly affected by the radiative heat transfer. To achieve accurate thermal radiation exchange between surfaces, it is important to calculate the radiation view factor precisely. Finer subdivision of meshes can be used to increase the accuracy of radiation view factor, but if the mesh is subdivided infinitely, the time required for calculation increases significantly and thus decreasing the efficiency. If the subdivision is not sufficient, assurance of accuracy is not guaranteed. In this paper, optimal mesh subdivision method using the solid angle has been successfully tested and found to be useful in increasing the efficiency of calculating the shape factors.
통계적 방법을 이용한 적외선 신호 대비값 계산 방법 연구
한국일(K.I. Han),최준혁(J.H. Choi),하남구(N.K. Ha),장현성(H.S. Jang),이승하(S.H. Lee),김동건(D.G. Kim),김태국(T.K. Kim) 한국전산유체공학회 2017 한국전산유체공학회지 Vol.22 No.1
Infrared signals are frequently used to detect objects exposed to wide variety of environmental conditions. Detection by infrared signature is accomplished by distinguishing objects by using the IR radiant contrast between objects and the background. There are several methods of estimating the IR radiant contrast. The inverse distance weighting method, which is one of the IR radiant contrast estimation method using the effect of distance from objects, is known to be an effective way to analyze radiant contrast for complex backgrounds. However this method has a disadvantage of requiring a long calculation time. In this study we propose a statistical method of estimating the IR radiant contrast by using randomly selected pixels of arbitrary number among background pixels to reduce calculation time. Some measured IR images in MWIR and LWIR regions are used to test the applicability of the method proposed and we found that the proposed method is very effective in determining the IR radiant contrast showing very rapid estimation with minar accuracy loss.