• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2002년도 춘계 학술대회논문집
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• pp.53-58
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• 2002

A three-dimensional incompressible Navier-Stokes solver is developed for the flow analysis around Micro Air Vehicle(MAV) designed by MACDL(Micro Aerodynamic Control and Design Lab), Seoul National Univ., Validations of this solver are presented for two cases, first flow over the circular cylinder with infinite length, second flow over infinite wing with wing section, E387 airfoil. Simultaneously, Wind Tunnel test is performed with Flatform Wire type sir-component balance and model designed by MACDL. The numerical results are also examined through comparison with experimental data.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2001년도 춘계학술대회 논문집
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• pp.135-139
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• 2001

This experimental study investigates the wake flow behind a pair of cylinders displaced normal to a free stream. In this experiment, the principal aim is to investigate the transition mechanism of the large vortex generating process in the wake having unique vortex shedding pattern. associated with the gap difference between the cylinders. The detailed visualization is carried out using the PIV measurement. The transition mechanism of the large generating vortex is clarified by showing the streak lines. the vorticity and the statistical fluctuating velocity distributions.

• 대한기계학회논문집B
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• 제23권7호
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• pp.901-910
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• 1999

Investigated In this paper is the shock reflection from a blunt body, In particular, a circular cylinder of 20 mm diameter, for the weak shock impinging in the range 1<$M_s$ <2. Pressure and shock speed are measured for various shock strengths. Double-pulse holographic interferograms are taken to study the unsteady flow field at $M_s=1.34$. These experimental results are, in overall, well compared with the unstructured adaptive finite volume computation of the Euler equations performed in this study. Correlation of incident and reflected shocks and shock-shock locus obtained by experiment, computation, and theory are presented in parallel.

• 대한조선학회지
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• 제18권3호
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• pp.1-9
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• 1981

In this paper, it is demonstrated that, with the distribution of lowest order concentrated(discrete) singularities of delta function nature, the solution to the linear free surface problem can be obtained with a remarkable degree of accuracy. The linear boundary value problem is formulated subject to boundary conditions for the determination of strengths of singularities; the simple sources above(not on) the free surface and the vortices on the body surface. Three sample calculation were performed` the flow about a submerged vortex of known strength, the flow past a submerged circular cylinder, and the flow around a hydrofoil section. The convergence of the numerical procedure is achieved with a relatively small number of elements. The final results are compared with those of the published works, and are considered very satisfactory.

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.576-581
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• 2016

해양환경에서 큰문제가 되고 있는 아주 작은 크기의 플라스틱 입자인 미세플라스틱(Microplastic)은 잔류성이 크고 생물축적성이 있는 잔류성 유기오염 물질(POP)을 잘흡착하여 해양환경과 먹이사슬에 지대한 피해를 끼친다. 본 연구에서는 해양에 존재하는 대표적인 미세플라스틱 uPVC와 입자상의 잔류성 유기오염 물질 PAH를 원형 실린더로 가정하여 해양 환경에서 침강하고 있는 미세플라스틱이 잔류성 유기오염 물질에 의해 오염될 가능성을 알아보았다 이를 위해 표층및 심층수 환경에서 반지름에 따른 충돌효율과 접촉 시간을 구하여 두 실린더가 접촉할 시간의 기댓값인 기대 접촉시간을 계산하였다.

• 에너지공학
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• 제4권1호
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• pp.126-139
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• 1995

저속의 압축성 유동장에서의 원형 실린더 주위의 유동 및 열전달특성을 해석하였다. 비압축성 유동장에서의 실린더 주위의 유동 및 열전달현상에 대하여는 실험과 수치해석을 포함한 광범위한 연구가 진행되어 왔으며 매우 잘 알려져 있다. 실린더 벽면과 주위 유동장의 온도차가 큰 경우, 밀도의 변화가 커지므로 유동장은 압축성 유체가 되나 지배 방정식의 복잡함과 적절한 수치해석 방법의 부족으로 실린더 주위의 유동장을 압축성유체로 해석한 경우는 매우 드물다. 현재 압축성유동 해석에 널리 사용되는 time marching algorithm은 저속의 유동장 해석시 지배방정식에 나타나는 eigenvalue들의 괴리에 의하여 수렴속도가 현저히 떨어지게 된다. 본 연구에서는 이와 같은 난점을 극복할 수 있는 time-derivative preconditioning 방법을 사용하여 온도차가 큰 유동장에서의 강제 및 혼합대류에 대한 계산을 수행하였고 이들의 열전달특성을 비교하였다. 강제대류의 경우 실린더 벽면 온도의 증가에 따른 밀도 감소의 영향은 유동장의 Re수를 감소시켜 확산의 영향을 증가시키면서, 혼합대류의 경우 부력의 영향은 가열되는 유동장의 범위와 재순환 영역을 강제대류에 비해 현저히 감소시킨다.

• 대한수학회지
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• 제42권3호
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• pp.447-455
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• 2005

In this article, we introduce the notion of pointwise 1-type Gauss map of the first and second kinds and study surfaces of revolution with such Gauss map. Our main results state that surfaces of revolution with pointwise 1-type Gauss map of the first kind coincide with surfaces of revolution with constant mean curvature; and the right cones are the only rational surfaces of revolution with pointwise 1-type Gauss map of the second kind.

• Journal of Advanced Marine Engineering and Technology
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• 제25권4호
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• pp.825-832
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• 2001

This study was experimentally performed to investigate freezing behavior of sea water along horizontal cooled a circular tube with bubbly flow. The experiments were carried out for a variety of parameter, such as sea water velocity, air-bubble flow rate, and cooled-tube temperature. The shape of freezing layer, freezing rate and salinity of frozen layer were observed and measured. And the flow patterns around cooled tube were visualized using the PIV to analyze the relationship between the flow structure and the freezing characteristics. It was found that the experimental parameters gave a great influence on the freezing rate and the salinity of the frozen layer.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2002년도 추계학술대회 논문집
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• pp.63-66
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• 2002

The Flow patterns around two cylinders in various arrangements were studied by a discrete vortex method. The flow for the surface of each cylinder was represented by arranging bound vortices at adequate intervals. The viscous diffusion of fluid was represented by the random walk method. The vortex distributions, streaklines, timelines and velocity vectors around two cylinders were calculated for centre-to-centre pitch rations of P/D=1.5 and 2.5, attack angles of $\alpha=0^{\circ},\;30^{\circ},\;60^{\circ},\;and\;90^{\circ}$, correspond to the photographs by flow visualization and the flow intereference between two cylinders in var ious arrangements was clearly visualized by a numerical simulation.

• 대한조선학회지
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• 제13권3호
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• pp.1-9
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• 1976

A numerical method for solving the boundary-value problem related to potential flows with a free surface and an experimental work are introduced in this paper. The forced heaving motion of cylinders with arbitrary shapes in water of finite depth are Considered here. The Fredholm integral equation of the first kind is employed in determining strengths of singularities distributed on the body surface. And the results obtained by the present method for the case of a heaving circular cylinder on water of finite depth agree well with existing results of earlier investigators.