• 한국산업융합학회 논문집
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• 제2권2호
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• pp.3-10
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• 1999

Recently, It is proceeding the project of offshore structures in the many contury. A hybrid boundary-integral method is developed for computing wave forces on floating bodies. In this method, using the cylindric boundary for deviding elements, it is convenient to analysis but is difficult to apply to the rectangular or slender bodies. Thus, in this paper, I propose the new method by using the fictitious vertical cylinder of arbitary cross-section and shows results of the numerical analysis for testing.

• 태양에너지
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• 제7권1호
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• pp.53-60
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• 1987

Natural convection in the annulus between concentric inclined cylinders has been studied by the numerical analysis. Governing equations are numerically solved by means of successive over-relaxation methods for a range in orientation from horizontal to vertical. It is found that flow patterns can also be observed the co-axial double spiral. As the angle of inclination is increased, the center of the eddy is shifted into the lower part of annulus and flow structure is apparently changed. In the present study, the maximum local Nusselt numbers for the inner and outer walls at the vertical cylinder increase more than those at the horizontal cylinder by 71%, 42% respectively. Consequently the effect of inclination on the heat transfer is considerably large.

• 한국해양공학회지
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• 제21권2호
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• pp.12-21
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• 2007

As the economy grows and the population increases, we need to develop our coastal area and make use of it for various purposes. Specifically, investigation of the wave interactions on and around the vertical cylinders is very important in the design of the offshore or coastal structures. The nonlinear potential analysis developed so far, although very useful, has been found to be limited in application, as strong nonlinear waves generated by the interference between multilayered cylinders and wave impact forces by breaking waves can hardly be estimated. In this study, using a 3-Dimensional volume tracking method VOF(Volume of Fluid), based on Namer-Stokes equations, was developed to simulate highly nonlinear effects, such as breaking waves at the interface or complicated interference waves among structures. A numerical method for nonlinear interaction wave and vertical cylinders is newly proposed. The wave forces and wave transformations computed by the newly proposed numerical simulation method were compared to the other researcher's experimental results, and the results agree well. Based on the validation of this study, this numerical method is applied to the two vertical cylinders to discuss their nonlinear wave forces and wave transformations, according to the variations of separate distance of vertical cylinders.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.274-278
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• 2004

A simultaneous measurement system that can analyze the flaw-structure interactions has been developed This system consists of four CCD cameras, two for capturing instantaneous flaw fields and two for tracking a solid body. The three-dimensional vector fields around a cylinder are measured while the motion of the cylinder forced by the flow field is measured simultaneously with the constructed system The cylinder is pended in the working fluid of a water channel and the surface of the working fluid is forced sinusoidal to make the cylinder bounced Reynolds number for the mean main stream is about l000. The interaction between the flaw fields and the cylinder motion is examined quantitatively.

• 한국해양공학회지
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• 제18권4호
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• pp.1-7
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• 2004

A simultaneous measurement system that can analyze the flow-structure interaction has been developed. This system consists of four CCD cameras, two for capturing instantaneous flow fields and two for tracking a solid body. The three-dimensional vector fields around a cylinder are measured, while the motion of the cylinder forced by the flow field is measured, simultaneously, with the constructed system. The cylinder is suspended in the working fluid of a water channel, and the surface of the working fluid is forced sinusoidally to make the cylinder bounced. Reynolds number for the mean main stream is about 3500. The interaction between the flow fields and the cylinder motion is examined quantitatively.

• 오토저널
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• 제5권1호
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• pp.89-93
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• 1983

This paper describes on experimental investigation into the heat dissipation of Diesel engine, placing emphasis on the variations of compression ratio and cooling water temperature. The engine used for this test was a vertical single-cylinder four-cycle type, having a direct injection. Engine performance and heat transfer rates was tested under the compression ratio 14.3 and 17.4. In this study, the results showed that output and transfer rates of engine decrease in accordance with the decrease of compression ratio. The effect of cooling water temperature and injection delay of fuel on the heat dissipation brings about the decrease of heat transfer rates from cylinder to cooling water.

• 한국기계기술학회지
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• 제13권2호
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• pp.101-106
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• 2011

In this study, the velocity distribution according to upper side coner shape of underwater construction with rectangular cylinder was measured with PIV method and the wake flow characteristics was considered. According to the coner shape, the flow pattern of wake flow was also differed greatly and the step-shaped coner of cut-off ratio B/H=0.06 was similar in the slope shape in result.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 추계학술대회 논문집(제1권)
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• pp.195-201
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• 2006

해양구조물에 유기되는 파랑력과 해양파에 의한 해양구조물의 운동특성에 대한 연구는 선형이론에 근거한 통계적인 방법에 의해 꾸준히 연구되어왔다. 이러한 연구는 선형이론의 제한성으로 인해 파 스펙트럼의 극한에 해당하는 극한파에 대해서는 적용하기 어려운 점이 있다. 본 연구에서는 간단한 구조물에 대하여 극한파에 의한 파랑력을 추정하는 수치기법을 개발하였다. 극한파는 선형 파랑 집중법을 이용하여 수치적으로 구현하여 바닥면에 고정된 수직 실린더에 작용하는 파랑력을 추정하였다. 또한 수직 실린더의 유탄성 응답을 고려하여 강체인 경우와 탄성체의 경우에서 극한파에 의한 파랑력 변화를 고찰하였다.

• 한국항해항만학회지
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• 제31권1호
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• pp.21-27
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• 2007

해양구조물에 유기되는 파랑력과 해양파에 의한 해양 구조물의 운동특성에 대한 연구는 선형이론에 근거한 통계적인 방법에 의해 꾸준히 진행되어왔다. 이러한 연구는 선형이론의 제한성으로 인해 파 스펙트럼의 극한에 해당하는 극한파에 대해서는 적용하기 어려운 점이 있다. 본 연구에서는 극한파에 의해 구조물에 작용하는 파랑하중을 추정하는 수치기법을 개발하였다. 수치기법으로는 변분법에 근거한 유한요소법을 사용하였다. 선형 파랑 집중법을 이용하여 수치적으로 극한파를 구현하였으며, 이를 이용하여 바닥면에 고정된 수직 실린더에 작용하는 파랑하중을 추정하였다. 또한 수직 실린더의 유탄성 응답을 고려하여 강체인 경우와 탄성체의 경우에서 극한파에 의한 파랑하중 변화를 고찰하였다.

• 에너지공학
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• 제21권1호
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• pp.18-25
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• 2012

굴뚝내 수직 원형관의 자연대류에서 굴뚝의 입구길이, 출구길이, 그리고 굴뚝의 직경에 따른 열전달 변화를 실험적으로 연구하였다. 상사성을 이용하여 열전달 실험 대신 물질전달 실험을 수행하였다. 직경 0.054 m, 높이 0.03, 0.07, 0.10 m의 원형관에 대하여 굴뚝의 직경을 0.06 m에서 0.14 m까지, 높이를 0.30 m에서 1.10 m까지 변화시켰다. 이는 Pr 수 2,094, $Ra_L$ 수 $4.55{\times}10^9$, $5.79{\times}10^{10}$, 그리고 $1.69{\times}10^{11}$에 해당한다. 굴뚝이 없을 때, 수직 원형관의 열전달은 Le Ferve의 수직평판에 대한 층류 자연대류 상관식과 일치하였다. 출구길이를 증가시키며 실험한 결과, 열전달은 증가하다가 특정 출구길이 이상에서는 일정해 졌다. 반면, 입구길이를 증가시킬 때는 열전달은 감소하다가 특정 입구길이 이상에서는 일정해졌다. 굴뚝효과로 증가된 열전달은 굴뚝의 직경을 증가시킬수록 감소하다가 굴뚝이 없을 때와 같아졌다.