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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.
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.
MCS를 이용한 자동차 공력 성능의 신뢰성 설계에 대한 연구
구요천(Yocheon Ku),노주현(Joohyun Rho),윤수환(Suhwan Yun),김태윤(Taeyoon Kim),이동호(Dongho Lee) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The objective of this study is the provision of the method to find the reliable ranges of the design variables where the required performances are satisfied. The reliability-based design optimization was performed to find the reliable ranges and the Monte Carlo Simulation was used to evaluate the probability of success. And the empirical model was adopted for the efficient prediction of the aerodynamic performances of an automobile. Through this study, the reliable ranges of the design variables with 2-sigma or 3-sigma could be found and there sizes were maximized for the design flexibility. The provided method is expected to improve the efficiency of the development process of a new automobile by reducing the iterations between the automobile external shape design and evaluation of the aerodynamic performances.
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.
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.
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.