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유한 수심에서 반원형 부유체의 부가질량계수 약산식 개발
구원철(Weoncheol Koo),김준동(Jun-Dong Kim) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.1
This study is to develop the simplified formulae for added mass coefficient of a 20D floating body with a semi-circle section in a finite water depth. The semi-circle floating body may represent a simplified midship section transformed by Lewis form, which can be used for the ship motion analysis by strip theory. Since the added mass coefficient varies with motion frequencies and sea bottom effect, the correction factor representing the effect of water depth and frequencies is developed for accurate prediction of added mass. Using a two-dimensional numerical wave tank (NWT) technique based on the boundary element method(BEM) including sea bottom boundary the reference values of added mass are calculated to develop the correction factor. For verification and effectiveness of the formulae, the predicted added mass coefficients for various frequencies and water depth ratios are compared with the calculated values from NWT technique.
주파수 영역에서 인공감쇠기법을 활용한 복층 유체의 수치조파수조 방사 문제
민은홍(Eun-Hong Min),구원철(Weoncheol Koo) 한국해양공학회 2017 韓國海洋工學會誌 Vol.31 No.1
There are two wave modes induced by an oscillating body on the free surface of a two-layer fluid: the barotropic and baroclinic modes. To investigate the generated waves composed of two modes, a radiation problem involving a heaving rectangular body was solved in a numerical wave tank. A new artificial damping zone scheme was developed and applied in the frequency-domain analysis. The performance of this damping scheme was compared with given radiation boundary conditions for various conditions. The added mass and radiation damping coefficients for the heaving rectangular body were also calculated for various fluid-density ratios.
수직 진자형 파력 발전 장치의 운동성능 및 파력 추출에 관한 실험적 연구
김성재(Sung-Jae Kim),구원철(WeonCheol Koo),민은홍(Eun-Hong Min),장호윤(Hoyun Jang),윤동협(Donghyup Youn),이병성(Byeongseong Lee) 한국해양공학회 2016 韓國海洋工學會誌 Vol.30 No.5
The aim of this study was to experimentally investigate the hydrodynamic performance of a hemispheric wave energy converter (WEC) and its wave power takeoff. The WEC is a heaving body-type point absorber with a hydraulic-pump power take-off (PTO) system. The hydraulic PTO system consists of a hydraulic cylinder, hydraulic motor, and generator, with consideration given to the hydraulic pressure and flow rate. Two body model shapes, including the original hemisphere and a bottom-chopped hemisphere, were considered. The heave RAOs of the two models were evaluated for various body drafts. The effects of the hydraulic PTO system on the RAOs were also investigated.
정현철(Hyen-Cheol Jung),구원철(WeonCheol Koo),김홍빈(Hong-Bhin Kim) 한국해양환경·에너지학회 2020 한국해양환경공학회 학술대회논문집 Vol.2020 No.7
이차원 미니조파수조에서 안정적인 실험을 위해서는 입사파의 반사를 최소화 할 수 있는 최적화 된 소파장치 설계가 필요하다. 이차원 미니조파수조는 피스톤 타입 조 파기를 사용하여 다양한 조건에서 규칙적인 입사파와 불규칙 파를 구현하고, 파-물체 상호작용을 실험할 수 있는 장치이다. 본 연구에서는 다양한 조건의 경사형 타공판 소파장치를 설치하여 입사파의 반사를 측정하기 위해 4점 반사분리법을 이용하여 반사파를 계산하였다. 타공판에 대한 경사도 및 공극률을 변화시키면서 다양한 입사파 조건에서 실험을 수행하고 결과를 분석하였다. An optimized design of wave absorber is required to remove the reflected waves in a two - dimensional experimental wave tank. The two - dimensional mini-wave tank is a device capable of generating regular and irregular incident waves under various conditions using a piston type wave maker and experimenting with wave-body interaction. In this study, the reflected wave was calculated using a four-point reflection separation method to measure the reflection of the incident wave with installing the inclined perforated plate wave absorber under various conditions. Experiments were conducted under various incident wave conditions while varying the inclination and porosity of the perforated plate and the results were analyzed.