• 수산해양교육연구
• /
• 제25권5호
• /
• pp.1102-1109
• /
• 2013

An numerical analysis was performed to obtain the design parameters for parallel micro-channels. The parallel micro-channels consist of 10 square channels with a hydraulic diameter of 300 ${\mu}m$ and inlet/outlet manifolds. The channel length is 5mm, 10mm and 40mm respectively. Mass flux was set between 200~600kg/m2s as inlet boundary condition and atmospheric pressure was set as outlet boundary condition. The pressure drop in channels and manifolds were estimated by using the Shah and London correlation and the flow uniformity was represented by the velocity distributions with dimensionless velocity. The results show that the flow uniformity in channels depends on shapes of manifolds, length and mass flux.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 하계학술대회 논문집 F
• /
• pp.1981-1983
• /
• 1998

The principle of the MHD generation is based on Faraday's law of induction that a eletromotive force(u ${\times}$ B) is generated when the working gas of velocity u flows a channel in which magnetic field of strength(B) exists. In MHD power generation system, enthalpy of the working gas is converted to electric power directly through expansion in generator channel. It means that electric power can be generated without moving mechanical linkage such as turbine blades. There are two types in the MHD generator; linear type Faraday and disk type hall generator. Disk type hall generator is the main target of this paper. Isentropic efficiency and enthalpy extraction rate of disk type shock tube driven hall generator is discussed here.

• 한국지구물리탐사학회:학술대회논문집
• /
• 한국지구물리탐사학회 2011년도 학술대회 및 정기총회
• /
• pp.187-188
• /
• 2011

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
• /
• pp.630-631
• /
• 2009

Recent developments such as concern over global warming, depletion of fossil fuels and increase in energy demands by the increasing world population has eventually lead to mass production of electricity using renewable sources. Apart from wind and solar, ocean holds tremendous amount of untapped energy in forms such as geothermal vents, tides and waves. The current study looks at generating power using waves and the focus is on the primary energy conversion (first stage conversion) of incoming waves for two different models. Observation of flow characteristics, pressure and the velocity in the augmentation channel as well as the front guide nozzle are presented in the paper. A numerical wave tank was utilized to generate waves of desired properties and later the turbine section was integrated. The augmentation channel consisted of a front nozzle, rear nozzle and an internal fluid region representing the turbine housing. The analysis was performed using the commercial CFD code.

• 해양환경안전학회:학술대회논문집
• /
• 해양환경안전학회 2005년도 추계학술대회지
• /
• pp.159-163
• /
• 2005

채널 내부의 비정상 흐름을 규명하기 위하여 실제 사용 중인 판형 열교환기 모델을 대상으로 가시화 실험과 입자영상유속계(PIV)를 사용한 계측을 수행하였다. 실험은 기복을 가지고 있는 채널의 높이와 내부유동의 부분 평균속도벡터에 따른 7가지 종류의 레이놀즈수를 적용하였고, 순간속도벡터분포와 유동특성을 고찰하였다. 실험에서 삼각형상 그루브 채널은 하부 채널과 채널 흐름에 의해서 받고 있는 전단응력의 그루브 흐름과의 관계에서 복합적인 흐름의 형태로 나타났다. 삼각형상 그루브와 채널 사이의 경계인 전단혼합층은 채널에서 난류강도가 상승하는 주흐름에 영향을 미쳤다.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제8권1호
• /
• pp.102-109
• /
• 2016

The hydrodynamic interaction between two large vessels can't be neglected when two large vessels are closed to each other in restricted waterways such as in a harbor or narrow channel. This paper is mainly concerned with the ship maneuvering motion based on the hydrodynamic interaction effects between two large vessels moving each other in curved narrow channel. In this research, the characteristic features of the hydrodynamic interaction forces between two large vessels are described and illustrated, and the effects of velocity ratio and the spacing between two vessels are summarized and discussed. Also, the Inchon outer harbor area through the PALMI island channel in Korea was selected, and the ship maneuvering simulation was carried out to propose an appropriate safe speed and distance between two ships, which is required to avoid sea accident in confined waters. From the inspection of this investigation, it indicates the following result. Under the condition of $SP_{12}{\leq}0:5L$, it may encounter a dangerous tendency of grounding or collision due to the combined effect of the interaction between ships and external forces. Also considering the interaction and wind effect as a parameter, an overtaken and overtaking vessel in narrow channel can navigate while keeping its own original course under the following conditions; the lateral separation between two ships is about kept at 0.6 times of ship length and 15 degrees of range in maximum rudder angle. On the other hand, two ships while overtaking in curved narrow channel such as Inchon outer harbor in Korea should be navigated under the following conditions; $SP_{12}$ is about kept at 1.0 times of ship length and the wind velocity should not be stronger than 10 m/s.

• Journal of Advanced Marine Engineering and Technology
• /
• 제28권8호
• /
• pp.1185-1194
• /
• 2004

Virtual images for PIV are produced for the construction of a benchmark test tool of PTV systems, Camera parameters obtained by an actual experiment are used to construct the virtual images, LES(Large Eddy Simulation) data sets of a channel flow are used for generation of the virtual images, Using the virtual images and the camera's parameters. three-dimensional velocity vectors are obtained for a channel flow. The capabilities of a 3D-PTV algorithm are investigated by comparing the results obtained by the virtual images and those by an actual measurement for the channel flow.

• 한국항해학회지
• /
• 제21권4호
• /
• pp.39-47
• /
• 1997

We researched the mechanism on th flucturain of Bottom Cold Water in the western channel of Korea Strait, using 13 years(1981~1933) oceanographic data of FRDA. The bottom cold water in the western channel appears more often in summer and fall than in winter and spring, and its year-to-year variation of temperature is very large. Such variation seems to be closely related with the variations of cold waters in the subsurface layer of the southwestern East Sea. According to the longitudinal temperature distribution along the korean southeastern coast, a density difference occurs all the time at the still deepth between the western channel and the southwestern East Sea. Thus, it is inferred that the cold waters would intrude into the western channle form the subsurface layer in the southwestern East Sea as a density-driven current, and it intensity depends upon the density difference.

• 한국정보통신학회논문지
• /
• 제18권5호
• /
• pp.1061-1066
• /
• 2014

천해에서 음파 전달은 매우 복잡하며, sparse한 전달 특성을 갖는다. 이러한 환경에서 수중음향통신 시스템의 성능을 향상시키기 위하여 채널을 추정하기 위한 여러 방법들이 연구되었다. 본 논문에서는 기존의 sparse-aware LMS(Least Mean Square) 알고리즘들보다 빠른 수렴속도를 갖는 LMS 기반 채널 추정 알고리즘을 제안하였다. 제안한 방법은 $L_p$-norm LMS 알고리즘과 soft decision 과정을 결합한 것이다. 모의실험은 실제 해상 실험을 통하여 얻은 수중 음속 데이터를 바탕으로 수행되었다. 그 결과 제안한 방법이 기존의 방법들보다 빠른 수렴속도와 향상된 성능을 보이는 것을 확인하였다.

• 수산해양교육연구
• /
• 제29권1호
• /
• pp.201-208
• /
• 2017

The major cause of the marine accidents is the collision with a moving object such as ship as well as the fixed object such as breakwater. Therefore, the most effective way to reduce the maritime ship accidents is the prevention of collision. In order to decrease the collision, it is principle that the navigation officer promptly judges the dangerous condition and makes the quick response. The ship does not allow any object or other ships approaching its surrounded area called ship area so that it prevents the collision. Generally, the ship which has high speed or poor maneuvering capability shall be managed from the distance so that the other ship does not invade its ship domains(watching distance, blocking distance). Accordingly, this study sets the navigational risk assessment model by applying ship dynamic domain and collision judgement method considered ship length, speed and navigational capability. It also reviewed the validity of the model and evaluated the perilous water way (Maenggol Channel) and a curved route near Maenggol Channel. As a result, in case of a ship with 100m in length passing Maenggol Channel, it represented "warning" level before 1.5nm to the entry, "dangerous"level 0.75nm before to it and "very dangerous" level 0.5nm before to it and then "dangerous"level again up to the entry. Applying to the curved route also showed the same results as the Narrow Channel or Maenggol Channel. This analysis highly matched with the actual navigation results. In the future, this model will be useful for coastal navigation safety chart development and safety evaluation for route or port development. It also allows to evaluate the dangerous route or the best route by applying the result into ECDIS so that it will finally help to reduce the marine accidents. Eventually the model will be effective for the marine traffic simulation evaluation forced by Maritime Traffic Safety Act.