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명노신(Rho Shin Myong),조태환(Tae Hwan Cho) 한국항공우주학회 2005 韓國航空宇宙學會誌 Vol.33 No.4
적대적 환경에서 임무를 수행하는 비행체의 레이다 포착에 관련된 스텔스 기술이 주요설계 문제로 부각되고 있다. 레이다 회피 기능을 증대시키는 방안들을 분석하기 위해서는 Maxwell 방정식을 해석하는 기법이 필요한데, 본 연구에서는 기본 수치기법으로 다학제 최적설계 연구에 적합한 CFD 기법을 이용하였다. 시간 영역 전자기장 데이터를 DFFT 알고리즘을 이용하여 주파수 영역으로 변환한 후, 근방-원방 변환에 기초한 Green 함수 관계식을 사용하여 RCS 특성을 예측하였다. 검증을 위해 완전전도 실린더 주위 TE 모드를 고려하였으며, CFD 기법을 원용한 CEM 코드의 가능성을 확인하기 위해 비행체 날개단면 주위의 전자기 산란 현상을 계산하였다. The ability to predict radar return from flying vehicles becomes a critical technology issue in the development of stealth configurations. Toward developing a CEM code based on Maxwell's equations for analysis of RCS reduction schemes, an explicit upwind scheme suitable for multidisciplinary design is presented. The DFFT algorithm is utilized to convert the time-domain field values to the frequency-domain. A Green's function based on near field-to-far field transformation is also employed to calculate the bistatic RCS. To verify the numerical calculation the two-dimensional field around a perfectly conducting cylinder is considered. Finally results are obtained for the scattering electromagnetic field around an airfoil in order to illustrate the feasibility of applying CFD based methods to CEM.
이원자 기체 유동 해석을 위한 일반유체역학 계산모델 개발
명노신(Rho-Shin Myong),조수용(Soo-Yong Cho) 한국전산유체공학회 2001 한국전산유체공학회 학술대회논문집 Vol.2001 No.-
The study of nonlinear gas transport in rarefied condition or associated with the microscale length of the geometry has emerged as an interesting topic in recent years. Along with the DSMC method, several fluid dynamic models that come under the genera1 category of the moment method or the Chapman-Enskog method have been used for this type of problem. In the present study, on the basis of Eu's generalized hydrodynamics, a computational model for diatomic gases is proposed. The preliminary result indicates that the bulk viscosity plays a considerable role in fundamental flow problems such as the shock structure and shear flow. The general properties of the constitutive equations are obtained through a simple mathematical analysis. With an iterative computational algorithm of the constitutive equations, numerical solutions for the multi-dimensional problem can be obtained.
Computational Investigation of Lightning Strike Effects on Aircraft Components
Ranjith, Ravichandran,Myong, Rho Shin,Lee, Sangwook The Korean Society for Aeronautical and Space Scie 2014 International Journal of Aeronautical and Space Sc Vol.15 No.1
A lightning strike to the aircraft seriously affects the aircraft and its components in various ways. As one of the most critical threats to the flight safety of an aircraft, fuel vapour ignition by lightning can occur through various means, notably through hot spot formation on the fuel tank skins. In this study, a coupled thermal-electrical approach using the commercial software ABAQUS is used to study the effects of a lightning strike on aircraft fuel tanks. This approach assumes that the electrical conductivity of a material depends on temperature, and that a temperature rise in a material due to Joule heat generation depends on electrical current. The inter-dependence of thermal and electrical properties-the thermal-electrical coupling-is analyzed by a coupled thermal-electrical analysis module. The analysis elucidates the effects of different material properties and thicknesses of tank skins and identifies the worst case of lightning zones.
Computational Investigation of Lightning Strike Effects on Aircraft Components
Ravichandran Ranjith,Rho Shin Myong,Sangwook Lee 한국항공우주학회 2014 International Journal of Aeronautical and Space Sc Vol.15 No.1
A lightning strike to the aircraft seriously affects the aircraft and its components in various ways. As one of the most critical threats to the flight safety of an aircraft, fuel vapour ignition by lightning can occur through various means, notably through hot spot formation on the fuel tank skins. In this study, a coupled thermal-electrical approach using the commercial software ABAQUS is used to study the effects of a lightning strike on aircraft fuel tanks. This approach assumes that the electrical conductivity of a material depends on temperature, and that a temperature rise in a material due to Joule heat generation depends on electrical current. The inter-dependence of thermal and electrical properties?the thermal-electrical coupling?is analyzed by a coupled thermal-electrical analysis module. The analysis elucidates the effects of different material properties and thicknesses of tank skins and identifies the worst case of lightning zones.