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응집구조 추출기법을 이용한 전방 계단에서의 난류 소음 원인 분해
조문환(Munhwan Cho),배영민(Young Min Bae),문영준(Young J. Moom) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The flow structures and acoustic sources are identified by coherent structure identification methods for the turbulent forward-facing step flow at Re<SUB>h</SUB>=8,000 [AIAA paper 2005-3006, S. Becker et al., 2005]. The identification methods like proper orthogonal decomposition (POD) and its complement method with others are applied to the turbulent flow and acoustic field, which are able to decompose the properties into each mode that has its own characteristics and energy level. These methods are not only to study the random fluctuated hydrodynamic and acoustic properties but also to extract the relation between the turbulent flow structures and the acoustic sources.
조문환(Munhwan Cho),이강덕(Kang-Duck Ih) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
The noise reduction effects according to various shape modifications in small gaps are studied in the case of outside mirror folding gaps in PB. The acoustic pressure can be calculated by numerical approach to the interaction between the gap shape and convecting point vortices in the potential flow field. It is shown that gap noise can be reduced when decreasing the height of the rear corner and the width of a vertical gap, and rounding off or chamfering the rear corner. Each attribution of these major control parameters to far-field wind noise can be compared and the optimized gap shape can be decided by means of DFSS analysis.
이명한(Myunghan Lee),조문환(Munhwan Cho),이강덕(Kangduck Ih),최의성(Euisung Choi) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.4
There are three significant noises from the sunroof while driving. Among them, sunroof tilt-up noise has mainly high-frequency characteristics in the side and rear openings of sunroof. Because of complex structures to operate sunroof, significant flow disturbance makes strong turbulent noise. In this study, sunroof tilt-up noise was predicted by using numerical simulation code and the results were compared with experimental data.
차량 실내 소음원 추적을 위한 독자적 음원 가시화 신기술 개발
이명한(Myunghan Lee),조문환(Munhwan Cho),이종현(Jonghyun Lee),이강덕(Kangduck Ih),김영기(Youngkey Kim) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
Vehicle interior noise visualization method could make it efficient to find the position of various wind noise sources. Modified beamforming method by spherical microphone array with 5 cameras is developed for sound source detection in the 360-degree surrounding plane. Especially, MEMS microphone is applied in order to reduce both of cost and weight of the device without any loss of detecting capability. Several kinds of annoying noise problems could be solved with efficiency and precision by applying the sound identification method.