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반응면 기법과 크리깅 기법을 이용한 설계공간의 타당성 향상
구요천(Yo-Cheon Ku),전용희(Yong-Heu Jeon),김유신(Yu-Shin Kim),이동호(Dong-Ho Lee) 한국항공우주학회 2005 韓國航空宇宙學會誌 Vol.33 No.2
본 연구에서는 근사모델을 이용하여 설계공간의 타당성을 높일 수 있는 방법을 제시하였다. 이때 설계공간을 이동시키기 위한 기준으로 Chebyshev Inequality를 사용하였다. 이를 공탄성을 고려한 항공기 익형 설계문제에 적용함으로써 타당성이 크게 향상됨을 확인하였으며 이렇게 구한 설계공간 내에서 최적화를 수행함으로써 보다 우수한 최적값도 얻을 수 있었다. 즉 설계공간 내에서 주어진 제약조건을 만족할 확률이 증가하였으며, 설계공간을 이동시킴으로써 보다 우수한 최적점이 설계공간 내에 포함되었다고 할 수 있다. 또한 이 과정에서 반응면 모델과 크리깅 모델, 두 가지 근사모델을 사용하여 정확성과 효율성, 실험점에 대한 강건성 등을 비교하였으며, 본 연구에서 설계한 문제의 경우 비교적 선형적인 특징으로 인해 반응면이 보다 우수한 결과를 보여줌을 확인하였다. In this research, a procedure to improve the feasibility of design space is proposed by an approximation model. The Chebyshev Inequality is used as the criterion of modification of design space. This procedure is applied to the aero-elastic transonic wing design problem and the feasibility of the design space is greatly improved. Also the optimization results are improved by appling this procedure. That is, the probability to satisfy all imposed constraints is increased and the better design points are included in design space after this procedure. And the use of both a second-order response surface model and the Kriging model is investigated and compared in accuracy, efficiency, and robustness as approximation models in this procedure for different sampling methods. As a result, the second-order response surface model is more appropriate for our application than the Kriging model, because it is linear enough to be fitted well by the response surface model.
구요천(Ku Yo-Cheon),노주현(Rho Joo-Hyun),윤수환(Yun Su-Hwan),곽민호(Kwak Min-Ho),이동호(Lee Dong-Ho) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-
A nose shape is strongly related with the aerodynamic performances of train. Therefore shape definition and aerodynamic performance analysis are important for train nose shape design. In this study, a new design method was suggested for train nose shape design by configuration function. To this end, the nose shape was classified by box type and each box shape is defined. After that the 3-D shape of train was defined as several mathematical functions by combination of each box shape. Also it was shown that the wind shield of driver"s seat and complex curves of surface can be expressed using superposition of functions. This methodology can be used for grid generation of numerical analysis, and applied to aerodynamic optimization design of nose shape.
터널 주행속도 향상을 위한 고속열차 전두부 형상 최적화
구요천(Ku Yo-Cheon),윤수환(Yun Su-Hwan),노주현(Rho Joo-Hyun),김규홍(Kim Kyu-Hong),이동호(Lee Dong-Ho),권혁빈(Kwon Hyeok-Bin) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-
The next generation of Korean high-speed train under development will be designed for the maximum operating speed of 350km/h and maximum speed of 400km/h. This high-speed operation may cause the noise and vibration problems around tunnel exit due to the higher micro-pressure wave than present level. In this study, the nose shape optimization was conducted for the countermeasure against these problems. Axi-symmetric solver was used for numerical simulation, and response surface was used for efficiency of optimization process. Also the multi-step optimization was conducted to find out more accurate optimal shape. Through these analysis and optimization, it was found out that the optimal nose shapes for minimization of micro-pressure wave are definitely different along the nose length variation. And the mechanism of micro-pressure wave reduction was closely investigated by the analysis of generation process of compression wave in tunnel. The results are expected to be used as design guideline for performance improvement of the next generatin of Korean high-speed train.
구요천(Ku Yo-Cheon),김종용(Kim Jong-Yong),윤수환(Yun Su-Hwan),노주현(Rho Joo-Hyun),이동호(Lee Dong-Ho),권혁빈(Kwon Hyeok-Bin) 한국철도학회 2005 한국철도학회 학술발표대회논문집 Vol.- No.-
The ballast-flying, induced by strong underbody train gust, may damage train underbody, wheel and even cause the safety problems. For this reason, a heighter is being used to prevent the ballast-flying phenomenon through underbody flow reduction. In this research, flow field around a heighter is numerically simulated. And the parametric study of various heighter shapes is performed to find out more effective heighter shape. Also the ballast-flying probabilities are calculated for various ballast types and train speeds.
타이어-휠가드 공간의 음장모드와 고주파성 로드노이즈의 상관성 연구
이종현,구요천,이진모,Lee, Jong Hyun,Ku, Yo Cheon,Lee, Jin Mo 한국음향학회 2016 韓國音響學會誌 Vol.35 No.4
타이어와 휠가드 사이의 공간은 타이어 패턴음의 전달경로가 된다. 본 논문에서는 타이어-휠가드 공간에서 발생하는 음향현상을 음장모드 분석과 휠 가드 표면에서 음압분포 가시화를 통해 규명하였다. 타이어 패턴음 저감을 위해 음향학적 댐퍼 역할을 수행하는 캐비티를 휠가드 표면상에 적용하였다. 실내소음은 2 dB(A) 감소하였는데, 본 연구에서 다룬 소음저감방법은 완성차 단계에서 원가/중량의 증가없이 실내음질을 개선하는 효과적인 방안이 될 것이라고 판단된다. The space between tire and wheel guard acts as a path for tire pattern noise transmission. In this study, acoustic phenomenon occurring in the tire-wheel guard space is investigated using acoustic mode analysis and visualization of the sound pressure distribution over the wheel guard surface. We introduced a cavity over the wheel guard surface to reduce the tire pattern noise, where the cavity acts as an acoustic damper. The interior noise was reduced by 2 dB(A), and the noise control measures treated in this study may provide an efficient method to improve interior sound quality without increasing cost and weight at the final stage of the vehicle development.
편측 주행을 고려한 고속철도 터널의 후드 형상에 대한 연구
곽민호(Kwak Min-Ho),구요천(Ku Yo-Cheon),윤수환(Yun Su-Hwan),노주현(Rho Joo-Hyun),이동호(Lee Dong-Ho) 한국철도학회 2009 한국철도학회 세미나자료 Vol.2009 No.5
When a train enters into the tunnel with high speed, a compression wave generated inside the tunnel has been studied as a one-dimensional phenomenon. However, one-dimensional approach can't analyze 3-dimensional flow effect in the vicinity of the train body. In this research, so as to overcome this weak point, a prediction method of the wavefront of a compression wave using steady state solution has been used for the parametric study considering 3-dimensional effects of the interactions between trains and tunnels. The effective hood shapes were deduced in both cases of the train's entry into the tunnel on the single track and on a side of the double track. As a result, in case of the train's entry on a side of the double track, the increase of compression wave value propagated to the tunnel inside have appeared compared with the train's entry on the single track. Also, a horizontally convex elliptic hood shape is more effective at the train's entry on a side of the double track for the purpose of a decrease of wavefront gradient of a compression wave.
노주현(Rho Joo-Hyun),구요천(Ku Yo-Cheon),윤수환(Yun Su-Hwan),곽민호(Kwak Min-Ho),박훈일(Park Hoon-Il),김규홍(Kim Kyu-Hong),이동호(Lee Dong-Ho) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-
Through Korean high speed train development project "G7 Leading Technology Development Project" from 1996 to 2002, HSR-350X has been developed. It can run the maximum operating speed of 350 ㎞/h. Basedon this technology, KTX-2 which will be served commercially has been developed till 2007. This paper introduces the aerodynamic analysis of the High-Speed EMU and shows the results of optimized aerodynamicnose shape design techniques and clean pantograph panhead original techniques study. These are the important parts of developments for high speed train which maximum speed is 400 ㎞/h. Especially for decrease of tunnel micro pressure waves, the optimized nose area distributions were derived and the characteristics of micro pressure wave were analyzed. The robust optimized pantograph panhead shapes investigated to improve the performance and decrease the vortex flow which is thought to be its noise source. These shapes are clean and robust to external disturbances like unsteady accelerated flow or side wind was derived. Finally aerodynamic performances was verified with PIV and smog visualization by wind tunnel test.
형상 최적화를 위한 Vehicle Modeling Function을 이용한 자동차 3차원 형상 구현
노주현(Joo-Hyun Rho),구요천(Yo-Cheon Ku),윤수환(Su-Hwan Yun),이동호(Dong-Ho Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
Representing a complex, three-dimensional shape, such as an automobile, requires a large amount of CAD data consisting of millions of approximated discontinuous points, which makes it difficult or even impossible to efficiently optimize the entire shape. For this reason, in this paper, function based design method is proposed to optimize the external shape of an automobile. A vehicle modeling function was defined in the form of a Bernstein polynomial to smoothly express the complex 2D and 3D automobile configurations. The sub-sectional parts of the vehicle modeling function are defined as section functions through classifying each subsection of a box model. It is shown that the use of the vehicle modeling functions has the useful advantages in an aerodynamic shape optimization.
노주현(Rho Joo-Hyun),구요천(Ku Yo-Cheon),윤수환(Yun Su-Hwan),곽민호(Kwak Min-Ho),박훈일(Park Hoon-Il),김규홍(Kim Kyu-Hong),이동호(Lee Dong-Ho) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-
Recent high-speed trains around the world have achieved remarkable improvement in speed. In Korea, the new high-speed train with maximum speed of 400㎞/h has been developing through the "Future High-Speed Rail System Project". The improvement in train speed brings numerous aerodynamic problems such as strong aerodynamic resistance, noise, drastic pressure variation due to the crosswind or passing by, micro-pressure wave at tunnel exit, and so on. Especially, the nose shape of high-speed train is closely related to the most of the aerodynamic problems. Also the pantograph has to be considered for noise prevention and detachment problems. In this paper, the project, "Research on the Aerodynamic Technology Advancement of the High-Speed EMU" is introduced briefly, which is one of the efforts for the speed improvement of the "HEMU400x". Finally, two main results of train nose and pantograph will be shown. First, the optimization of the cross-sectional area distribution of the high-speed train nose to reduce tunnel micro-pressure wave, and second, robust design optimization of the panhead shape of a pantograph.