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宋武錫 홍익대학교 산업기술연구소 2003 産業技術 Vol.13 No.-
The artificial circulators (or aerators) are used to destroy any thermal stratification that are responsible for the degradation of water quality of lakes. About 370 such units are under operation in Korea and two circulator types, diffuser type and Intermittent hydraulic jet type(IHJC), are most common. IHJC produces ascending flow by using air bubbles released instantly near the bottom of the lake into a cylindrical pipe installed vertically. Differently form the diffuser-aerators, they can pull up the cold, oxygen depleted water directly to the region of the free surface, and they are believed to work effectively especially for relatively deeper lakes. Their design procedure has not been established yet though, and we propose a model focusing on the exit flow velocity at the top of the aerator by integrating the information from the examination of presently operating devices. The basic concept is balancing the bubble buoyance with the upward force to accelerate the water volume in the cylinder. The model is simple but believed to provide physically meaningful results reflecting the phenomena observed in real flows. In order to verify the model a model scale experiment is necessary.
송무석,김문찬,In-Rok Do,이신형,Ju Hyun Lee,현범수 대한조선학회 2012 International Journal of Naval Architecture and Oc Vol.4 No.3
Three types of 100 kW-class tidal stream turbines are proposed and their performance is studied both numerically and experimentally. Following a wind turbine design procedure, a base blade is derived and two additional blades are newly designed focusing more on efficiency and cavitation. For the three designed turbines, a CFD is performed by using FLUENT. The calculations predict that the newly designed turbines perform better than the base turbine and the tip vortex can be reduced with additional efficiency increase by adopting a tip rake. The performance of the turbines is tested in a towing tank with 700 mm models. The scale problem is carefully investigated and the measurements are compared with the CFD results. All the prediction from the CFD is supported by the model experiment with some quantitative discrepancy. The maximum efficiencies are 0.49 (CFD) and 0.45 (experiment) at TSR 5.17 for the turbine with a tip rake.
호수의 온도성층 파괴를 위한 산기식 강제순환장치의 용량평가
宋武錫,姜賢善 홍익대학교 산업기술연구소 2002 産業技術 Vol.12 No.-
Artificial aerations near the bottom of thermally stratified lakes have been widely used to manage the problems associated with the frequent algae blooming in the summer. Though over 370 aeration units are being used in Korea, the effectiveness or proper design procedure of such devices are not yet clearly understood. Here, a simple numerical experiment was performed aiming at the estimation of adequate aerator power to overcome the given thermal potential energy for a sufficient mixing of the lake. The bubble plume was modeled as a cylinder of a certain diameter and a rising speed. The experiment showed that a proper unit can mix a significant volume of thermally stratified water. The effective radius of the bubble plume was appeared to reach up to 6 times of the depth.
宋武錫 홍익대학교 산업기술연구소 2000 産業技術 Vol.10 No.-
Two-dimensional inviscid vortex-in-cell method with front tracking is developed and the method is proved to be able to handle multi-fluid problems including complicated interfacial phenomena with relatively modest computing efforts. Rayleigh-Taylor instability is simulated by using the developed method and the results demonstrated the reliability of the method for wide parameters' range. For long time simulations, interface merging needs to be further studied.
선박의 자세제어를 위한 발라스트수 이송 모델에 관한 연구
宋武錫 弘益大學校 産業技術硏究所 2004 産業技術 Vol.14 No.-
A formulation was reviewed to setup an experimental study aiming at investigation of the friction loss factor associated with the orifices connecting ballast tanks of ship. The shape and the relative position of the orifice to water level are to be varied with a given hydrostatic pressure condition and the flow rate will be measured. The flow coefficients obtained in this study can be effectively adopted for the prediction of the performance in ballasting and de-ballasting operation.
宋武錫 홍익대학교 산업기술연구소 1999 産業技術 Vol.9 No.-
Jonsson's study is briefly reviewed. Korean shipbuilding has followed the similar procedure which many early large scale shipbuilding countries had been through, but it has its own special characteristics associated with her historical legacy. Korea has become the world's first shipbuilder in terms of received order and this strikingly dramatic development is contributed to several important aspects. Japanese occupation between 1910-1945 provided Korean, to some extent, with basic shipbuilding skills and educated engineers, some of them played a crucial parts in educating naval architects later on. The high regard for education is an important asset for Korea and the abundance of such high educated naval architects made the quick absorption of the advanced foreign technologies possible. The government shipbuilding promotion policies also played key roles in enhancing shipbuilding in Korea. The amount of domestic delivery of ship has been rather underestimated but, as seen in the case of Sweden, the balance between export and domestic demand is very important.
宋武錫 홍익대학교 산업기술연구소 1998 産業技術 Vol.8 No.-
Oil bubble formation during the underwater oil discharge is investigated experimentally. The focus is placed on the size of the bubbles formed with the variation of discharge speed and nozzle diameter. Basically three types of bubble plume are formed in which different bubble formations are revealed according to the Reynolds number based on the nozzle diameter. The trend is from well established single bubble train to complex bubble clouds composed of the droplets of various size as the Reynolds number increases. Once bubbles are formed each bubble or bubble groups rise toward the free surface with showing various inter-bubble interactions by which the rising speed of the discharged oil is affected.
宋武錫,강현선 홍익대학교 산업기술연구소 2001 産業技術 Vol.11 No.-
A numerical study for the electrolyte flow of Lithium/Thionyl Chloride Battery is performed and the applicability of the developed algorithm for a further study is examined. Conservatives forms of each related governing equation is solved by finite volume based numerical scheme and a few test cases studied with several known velocity profiles. Further modelings of various source terms are required.