• Journal of the Society of Naval Architects of Korea
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• v.55 no.1
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• pp.1-8
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• 2018

A cavitator plays an important role to generate the supercavity. Most previous numerical and experimental studies have been focused on the presence of cavitators alone. However, the body behind the cavitator causes a change in the wake flow and hence it affects generation and growth of the supercavity. In this paper, we present a boundary elementary method based on a potential flow analysis, and calculate characteristics of the supercavity formation depending on the change of the body shape of two-dimensional submerged objects. Various parameters such as cone angle of the cavitator, length of the forehead and diameter of the body are considered. The results show that the longer the forepart length, the longer the cavity is created under the same conditions, and also the change in the diameter of the body is the most influential factor on the growth of the supercavity. As a result, we suggest that it is necessary to carefully consider the influence of the body shape during the initial design stage of the supercavitating underwater vehicle.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.1
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• pp.25-32
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• 2014

Recently supercavitating torpedo has been studied because of its high-speed performance as the next generation of underwater weapon systems. In this study, we present a numerical method based on the potential flow. Characteristic features of the shape of supercavities and drag forces are investigated. In addition, we introduce a viscous-potential method to compensate for the effects of viscosity. The results are compared with viscous calculations using a commercial package, FLUENT V13.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.6
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• pp.482-489
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• 2018

Most of the numerical and experimental studies on supercavitating flows are focused on the cavitator only. However, the partial cavity growing into the supercavity is affected by the shape of the body placed behind the cavitator. In this paper, we develope a numerical method which is based on the boundary element method to predict supercavitating flow around three-dimensional axisymmetric bodies. We estimate the influence of the body shape on the supercavity growth. Here, we consider various parameters of the body such as cavitator shape, shoulder length and body diameter, and compare the results with the case of the cavitator only. In summary, it is found that the body may impede the cavity growth, the shoulder mainly affects the cavity length, and the supercavity occurring in the cone type cavitator is strongly influenced rather than that of the disk type cavitator.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.4
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• pp.214-224
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• 2021

Recently, as the technology of the supercavitating underwater vehicle is improved, the necessity of research for maneuvering characteristics of the supercavitating underwater vehicle has emerged. In this study, as a preliminary step to analyzing the maneuverability of a supercavitating underwater vehicle, the characteristics of cavity shapes and hydrodynamic forces generated in a supercavitating underwater vehicle with an angle of attack were evaluated numerically. First, the geometry was designed by modifying the shape of the existing supercavitating underwater vehicle. The continuity and the Navier-stokes equations are numerically solved, and turbulent eddy viscosity is solved by the k-ω SST model. The results present the characteristics of cavity shape and the hydrodynamic forces of the designed geometry with an angle of attack.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.2
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• pp.112-122
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• 1993

A potential-based panel method is presented for the analysis of a partially or supercavitating two-dimensional hydrofoil at a finite submergence beneath a free surface, treating without approximation the effects of the finite Froude number and the hydrostatic pressure. Free surface sources and normal dipoles are distributed on the foil and cavity surfaces, their strength being determined by satisfying the kinematic and dynamic boundary conditions on the foil-cavity boundary. The cavity surface is determined iteratively as a part of the solution. Numerical results show that the wave profile is altered significantly due to the presence of the cavity. The buoyancy effect due to the hydrostatic pressure, which has usually been neglected in most of the cavitating flow analysis, is found playing an important role, especially for the supercavitating hydrofoil; the gravity field increases the cavity size in shallow submergence, but decreases it when deeply submerged, while the lift reduces at all submergence depth.

• Bulletin of the Society of Naval Architects of Korea
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• v.49 no.3
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• pp.13-18
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• 2012

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.159-173
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• 1991

This paper describes a potential-based panel method formulated for the analysis of a super-cavitating two-dimensional hydrofoil. The method employs normal dipoles and sources distributed on the foil and cavity surfaces to represent the potential flow around the cavitating hydrofoil. The kinematic boundary condition on the wetted portion of the foil surface is satisfied by requiring that the total potential vanish in the fictitious inner flow region of the foil, and the dynamic boundary condition on the cavity surface is satisfied by requiring thats the potential vary linearly, i.e., the tangential velocity be constant. Green's theorem then results in a potential-based integral equation rather than the usual velocity-based formulation of Hess & Smith type. With the singularities distributed on the exact hydrofoil surface, the pressure distributions are predicted with improved accuracy compared to those of the linearized lilting surface theory, especially near the leading edge. The theory then predicts the cavity shape and cavitation number for an assumed cavity length. To improve the accuracy, the sources and dipoles on the cavity surface are moved to the newly computed cavity surface, where the boundary conditions are satisfied again. This iteration process is repeated until the results are converged. Characteristics of iteration and discretization of the present numerical method are much faster and more stable than the existing nonlinear theories. The theory shows good correlations with the existing theories and experimental results for the super-cavitating flow. In the region of small angles of attack, the present prediction shows and excellent comparison with the Geurst's linear theory. For the long cavity, the method recovers the trends of the Wu's nonlinear theory. In the intermediate regions of the short super-cavitation, the method compares very well with the experimental results of Parkin and also those of Silberman.

• Digital Contents
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• no.9 s.148
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• pp.20-22
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• 2005

가상현실 분야에서 세계적인 기술력을 인정받고 있는 독일 프라운호퍼 IGD(Institute for Computer Graphics)의 한국 R&D센터 인 그래픽스연구원(IGI). IGI는 정보통신부와 독일 프라운호퍼 IGD, 이화여대가 공동으로 지난해 5월 설립한 국제공동연구기관(재단법인)이다. 의료 영상 처리 및 3차원 구성·원격 진료 시스템·영상 융합 프로젝트 등의 응용 개발 기술을 보유하고 있는 IGI는 IGD가 보유하고 있는 선진 컴퓨터 그래픽스 기술의 국내 도입을 뛰어 넘어 국내 VR(Virtual Reality) 기술력을 선진국 수준으로 끌어올리는데 견인차역할을하기위해국경을초월한연구원들이연구개발에한창이다.

• 한국정보교육학회:학술대회논문집
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• 2004.08a
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• pp.171-178
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• 2004

현대사회는 산업사회의 발달에 따른 물질 만능주의로 인해 이기적이고 배타적인 사회풍조가 사회 전반으로 점차 확산되면서 전통적 가치관이 경시되고 공동체 의식이 퇴색되어 가고 있는 실정이다. 그러나 인터넷의 발달은 시공간을 초월하여 가정과 학교가 가상의 공간에서 정보의 공유와 상호작용을 할 수 있게 해 줌으로써 웹을 활용한 인성교육이 가능해졌다. 본 논문에서는 이러한 웹의 특성을 활용하여 학습자가 다양한 체험활동 중심의 인성교육을 마을 단위로 실천하도록 한 후 웹 상에 구축된 인성교육 시스템을 이용하여 자신이 체득했던 체험활동 정보를 서로 공유하고 학생, 교사, 학부모가 상호 작용하게 함으로써 학습자가 지속적으로 인성 교육에 관심과 흥미를 갖고 참여할 수 있도록 하는 공동체 의식 함양을 위한 인성교육 시스템을 설계하였다. 더 나아가 웹기반 인성교육 시스템을 통해 마을을 사랑하는 마음과 공동체 의식을 함양하여 마을에 대한 긍지와 자부심을 갖고 상부상조하는 전통을 가꾸어 나가는데 도움을 주고자 한다.

• Proceedings of the Korea Association of Information Systems Conference
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• 2004.05a
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• pp.288-303
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• 2004

본 연구에서는 인터넷이 등장한 이후 인터넷의 사용이 보편화되면서 사이버 커뮤니티에 대한 관심과 참여하고 있는 사람들의 숫자가 급증하였다. 그러므로 사이버 커뮤니티의 시${\cdot}$공간의 제약 초월, 인터넷 공동체, 수평적 구조, 인터넷 방송, 인터넷 비즈니스 등의 다양한 순기능과 인터넷 상의 윤리적 문제, 익명성, 비대면성 등에서 발생되는 역기능의 실태, 사이버 커뮤니티의 활용에 대해서 조사분석을 실시하였다. 이를 위하여 사이버 커뮤니티의 개념부터 사이버 커뮤니티의 특징, 사이버 커뮤니티의 순기능과 역기능을 살펴본 후, 주 대상자 20대의 대학생으로 한 설문조사를 통해 사이버 커뮤니티의 순기능과 역기능에 대한 생각에 대해 알아보았다.