• 한국소음진동공학회논문집
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• 제26권2호
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• pp.203-209
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• 2016

According to the wear detection history for the steam generator tubes in the nuclear power plant, the outer tubes inside the steam generator have more problems on the flow-induced vibration than inner tubes. Many researchers and engineers have used a specified added mass coefficient for a given tube array during the design stage of the steam generator even though the coefficient is not constant for entire tube in cylindrical shell. The aim of this study is to find out the distribution of added mass coefficients for each tube along the radial location. When numbers of tubes inside a cylindrical shell are increased, values of added mass coefficients are also increased. Added mass coefficients at outer tubes are less than those of inner tubes and they are decreased with increasing the gap between the outermost tube and the cylindrical shell. It also turns out when the gap between the outermost tube and the cylindrical shell approaches infinite value, the added mass coefficient converges to an asymptotic value of given tube array in a free fluid field.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 추계학술대회 논문집
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• pp.164-168
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• 2001

The motion of a ship advancing in regular waves is analyzed in the time-domain using the convolution integral of the radiation forces. The memory effect functions and infinite frequency added masses are obtained from the solution of the three dimensional improved Green integral equation in the frequency domain by making use of the Fourier transformation. The ship motions in regular waves have been calculated by both the time and frequency domain methods. It has been shown that they agree very well with each other. The present time-domain method can be used to predict the time histories of unsteady motions in irregular waves. It can also be used to calculate the hydrostatic and Froude-Krylov forces over the instantaneous wetted surface of the ship hull to predict large ship motions, in a practical sense, advancing in large amplitude waves.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.105-108
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• 2003

The local motion at the top of an A-frame fixed on a research vessel for deep sea ROV floating in irregular waves is studied in the time-domain. The motion is analyzed in the time-domain using the convolution integral of the radiation forces. The memory effect functions and infinite frequency added masses are obtained from the solution of the three dimensional improved Green integral equation in the frequency domain by making use of the Fourier transformation.

• Journal of Ship and Ocean Technology
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• 제10권1호
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• pp.10-26
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• 2006

The radiation problem for oscillating bodies on the free surface has been formulated by the over-determined Green integral equation, where the boundary condition on the free surface is satisfied by adopting the Kelvin-type Green function and the irregular frequencies are removed by placing additional control points on the free surface surrounded by the body. The B-Spline based higher order panel method is then applied to solve the problem numerically. Because both the body geometry and the potential on the body surface are represented by the B-Splines, that is in polynomials of space parameters, the unknown potential can be determined accurately to the order desired above the constant value. In addition, the potential expressed in B-Spline can be differentiated analytically to get the velocity on the surface without introducing any numerical error. Sample computations are performed for a semispherical body and a rectangular box floating on the free surface for six-degrees of freedom motions. The added mass and damping coefficients are compared with those by the already-validated constant panel method of the same formulation showing strikingly good agreements.

• 대한조선학회논문집
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• 제29권1호
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• pp.55-60
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• 1992

본 논문에서는 선형포턴셜이론을 이용하여 제한수로에 놓인 2차원 주상체에 작용하는 동유체력과 운동응답의 특성을 고찰하였다. 유체영역을, 수로입구영역 그리고 수로영역으로 구분하여 우선 각 영역에서 해를 독립적으로 구한 다음 이를 인접영역의 해와 정합시켜 완전해를 구하였다. 수로의 길이보다 대략 4배가 긴 파장의 입사파는 수로내 유동을 공진시킨다. 이때 주상체에 작용하는 부가질량은 음의 값을 갖게 되며 동유체감쇠력은 급격한 변화를 보이고 주상체의 수평운동은 최대가 됨을 밝혔다.

• 마이크로전자및패키징학회지
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• 제18권1호
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• pp.29-33
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• 2011

전류밀도는 전기도급법에서 생산성과 직접적인 연관이 있고, 생산성의 증가를 위해선 고전류밀도가 필요하다. 회전전극(RDE)의 회전 속도를 증가시키면 고유속을 얻을 수 있다. 유속 조절을 위해 회전전극과 원통형 회전 전극을 사용하였고, 전압과 전류의 관계를 알아보기 위해 정전류, 정전압 실험과 linear sweep voltammetry 실시하였다. 회전 전극의 회전 속도가 400 rpm이상 조건에서, 수소가 발생하지 않고 1000 A/$m^2$이상의 최대전류멸도가 가능하였다. $25^{\circ}C$와 $62^{\circ}C$ 조건에서 구리의 확산계수는 각각 $5.5{\times}10^6\;cm^2\;s^{-1}$와 $10.5{\times}10^6\;cm^2\;s^{-1}$로 계산되었다. 수소가 발생하지 않으면서 안정적으로 구리를 전착할 수 있는 조건은 -0.05 V (vs Ag/AgCl)이었다. 첨가제인 glue와 thiourea-를 넣음으로써 구리의 침상성장을 막을 수 있었다. 표면 거칠기는 UV-Vis Spectrophotometer를 아용하여 분석되었다. 600 nm 영역에서 반사도는 측정 되었고 표면 거철기가 개선될수록 표면 반사도가 증가하였다.