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충격파가 존재하는 유동에서 Aero-optical Linking Equation의 적용 가능성에 관한 수치해석 연구
Numerical Study on the Applicability of Aero-optical Linking Equation in the Flow with Shock Waves

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Authors
김주호
Advisor
김종암
Issue Date
2021-02
Publisher
서울대학교 대학원
Keywords
전산유체역학Large Eddy Simulation (LES)공기광학천음속 유동충격파Optical Path Difference (OPD)Aero-optical Linking EquationComputational Fluid Dynamics (CFD)Aero-opticsTransonic flowShock Waves
Description
학위논문 (석사) -- 서울대학교 대학원 : 공과대학 항공우주공학과, 2021. 2. 김종암.
Abstract
본 연구에서는 충격파가 존재하는 천음속 유동에서 aero-optical linking equation의 적용 가능성에 관한 수치 분석을 진행하였다. 수치해석은 유동해석 데이터를 기반으로 Optical Path Difference (OPD) 분석을 진행할 수 있는 OPD 분석 코드와 정상상태 유동해석 데이터를 이용하여 비정상상태 OPD 항을 모델링하는 aero-optical linking equation 코드를 이용하였다. Linking equation 자체의 검증을 위해 Large Eddy Simulation (LES) 데이터를 이용하여 covariance function을 계산한 general linking equation의 경우 직접 계산한 비정상상태 OPD 항과 매우 일치하는 결과를 보여주었다. 하지만 실제 linking equation의 적용을 위해 Gaussian 혹은 exponential approximation을 이용한 linking equation with approximation의 경우 일관되지 못한 오차율, 부정확한 covariance peak과 second peak, negative covariance 값, 고려되지 못한 압축성 효과 및 충격파 문제 등으로 인해 정확도가 낮은 결과를 보여주었다. 분석 내용을 검증하기 위해 covariance approximation을 보완하기 위한 weighting function들을 적용해보았으며 기존 식을 적용하였을 때 나타났던 문제점들을 다소 해결하여 제시한 개선 방향이 효과가 있다는 것을 검증할 수 있었다.
In this study, a numerical analysis on the applicability of aero-optical linking equation was performed in a flow with shock waves. Optical path difference analysis code, which calculates the OPD based on flow results, and aero-optical linking equation code, that makes modeled unsteady OPD term by steady flow results, were used for numerical analysis. In case of general linking equation which is calculated with covariance function from Large Eddy Simulation (LES) results, results are exactly same with directly calculated unsteady OPD term. And these results showed that the linking equation itself is valid in a flow with shock waves. However, linking equation with approximations which is used Gaussian or exponential approximation for practical uses, showed inaccurate results. And these errors are come from the incoherent error tendency problem, inaccurate covariance peak value and second peak problem, unconsidered compressibility and shock wave problem, and negative covariance value problem. In order to validate the analysis results, weighting functions are applied to supplement the traditional covariance approximations. By solving some of the problems that appeared when the traditional approximation was applied, the proposed improvement directions were verified their effectiveness.
Language
kor
URI
https://hdl.handle.net/10371/176307

https://dcollection.snu.ac.kr/common/orgView/000000165915
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College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of AeroSpace Engineering (항공우주공학과)Theses (Master's Degree_항공우주공학과)
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