• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.573-574
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• 2006

This research deals with the wave transmission and dissipation problems for two dimensional regular waves and s vertical circular cylindersr. Using the unsteady mild slope equation, a numerical model has been developed to calculate the reflection and transmission of regular waves from a multiple-row vertical circular cylinders. In addition hydraulic model experiments have been conducted with different values of properties between the cylinders and opening ratio (distances) between the rows of the cylinders. It is found that the transmission coefficients decrease with decreasing the opening ratio and increasing the rows of vertical cylinders. Comparison between hydralic and numerical experiments results shows resonable agreement.

• 한국해양공학회지
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• 제10권3호
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• pp.89-95
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• 1996

The flow field around four cylinders for various angles was investigated utilizing particle image velocimetry(PIV) technique. Flow field was recorded by video camera first. Then application of PIV technique was done to the flow field. The results turned out to be useful to analyze complex flow field around multiple cylinders.

• 한국음향학회지
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• 제11권4호
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• pp.22-30
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• 1992

섬유강화 복합재료의 동탄성계수와 감쇠특성을 규명하기 위하여 랜덤하게 분포된 무한 실린더 형상의 산란계를 가진 메질내에서, 축방향으로 분극되어 조화운동을 하는 탄성파의 전파에 관하여 연구하였다. 단일 실린더에 대한 산란계수로부터 Lax의 준결정근사법을 이용하여 다중산란에 관한 이론을 유도하였고, 매질내에서의 파동전파특성을 내포하는 분산관계식을 얻었다. 다중 산란에 의한 실린더간의 상호작용을 수식화하기 위하여 필요한 실린더의 쌍분포함수는 몬테카를로 모의실험을 이용하여 구하였다. 수치적으로 구한 감쇠계수 및 유효전단강성을 주파수와 면적밀도의 함수로 제시하였다.

• 한국해양공학회지
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• 제22권4호
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• pp.27-33
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• 2008

One of the central problems in astudy of the coastal surface wave environment is predicting the transformation of waves as they propagate toward the shore. The transformation is mainly due to the existence of obstacles, such as breakwaters and vertical cylinders. In general, the types of wave transformation can be classified as follows: wave diffraction, reflection, transmission, scattering, radiation, et al. This research dealtwith wave transmission and dissipation problems for two dimensional irregular waves and vertical circular cylinders. Using the unsteady mild slope equation, a numerical model was developed to calculate the reflection and transmission of regular waves from a multiple-row circular breakwater and vertical cylinders. In addition, hydraulic model experiments were conducted with different values for the properties between tire piles and the opening ratio (distances) between the rows of the breakwater. It was found that the transmission coefficients decreased with a decrease in the opening ratio and an increase in the rows of vertical cylinders. A comparison between the results of hydraulic and numerical experiments showed reasonable agreement.

• 한국해양공학회지
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• 제15권4호
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• pp.14-19
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• 2001

In this paper, the wave and current forces acting on cylinders are investigated by theoretical and experimental methods. The models used are one-cylinder, four-cylinder and semi-submersible types. The theoretical investigations are carried out by the Morison equation and three dimensional source distribution method to calculate exciting forces in waves with and without currents. The experimental investigations are carried out in the wave tank which can generate currents in both directions. In these tests, the models have been exposed to the regular waves with and without currents. It is shown that the exciting forces acting on the one-cylinder or four-cylinders can be approximately estimated by the Morison equation and also by the diffraction theory. However, the Morison equation seems to be not appropriate to estimate the exciting forces on the present type of semi-submersible.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 추계학술대회 논문집
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• pp.190-195
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• 2001

Flow patterns are very complex and interactive between cylinders. The patterns are turbulent and non-linear caused by various factors. In this paper, flow patterns and pressure gradient around vertical cylinders were investigated by experiment. Changing gaps between cylinders the flow patterns are measured at a fixed coming velocity. Flow patterns showed very complex and closely related to the coming velocity and cylinder space. The pressure gradient around the flow field is observed by twelve hole pitot tubes and manometer. The experiment has been conducted in circulating water channel with PIV system. That can visualize flow patterns. The laser beam was used to reflect the image from particles and recorded by CCD camera. The cylinders were spaced from ID to 5D with 0.5m/sec of incoming flow velocity. The experimental results using pitot tube showed in good agreement with results of precious by others study. The results can be applied in the understanding and design of multiple pile array structures.

• 한국해양공학회지
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• 제15권1호
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• pp.12-18
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• 2001

This study concentrates on the second-order diffraction problem around circular cylinders in multi-frequency waves. The method of solution is a time-domain Rankine panel method which adopts a higher-order approximation for the velocity potential and wave elevation. In the present study, the multiple second-order quadratic transfer functions are extracted from the second-order time signal generated in random waves, and the comparison with other bench-mark test results shows a good agreement. This approach is directly applicable to prediction of nonlinear forces on offshore structures in random ocean.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.173-176
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• 2001

Several dielectric as well as conducting cylinders buried in the lossy half space are reconstructed from the scattered fields measured along the interface between the air and the lossy ground. Iterative inversion method by using the hybrid optimization algorithm combining the genetic and the Levenberg-Marquardt algorithm enables us to find the positions, the sizes, and the medium parameters such as the permittivities and the conductivities of the buried cylinders as well as those of the background lossy half space. Illposedness of the inversion caused by the errors in the measured scattered fields are regularized by filtering the evanescent modes of the scattered fields out.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1996년도 춘계 학술대회논문집
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• pp.105-110
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• 1996

In the present paper, flow fields around two dimensional single and two circular cylinders are analysed by a finite difference method. Navier-Stokes and the continuity equations an solved to simulate the flow fields. A overlapped grid system(the composite of a body boundary-fitted grid system near the body and a rectangular grid system for other flow fields) is used for this calculation. In the use of overlapped grid system, it is most significant thing to exchange the physical quantities from one grid system to the other one continuously, In this research, the linear interpolations of physical quantaties are done for this purpose in the overlapped region. The numerical calculations are carried out for the flows around a circular cylinder and two cylinders to verify the accuracy of present method. The flow fields around two cylinders facing the flow with side by side and tandem arrangement are analysed. The results are compared to other experimental and computational ones done in other single grid system.

• 산업경영시스템학회지
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• 제18권34호
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• pp.35-42
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• 1995

In the plastic extrusion process, product quality is influenced by work condition for temperature of cylinders and dies. The work conditions are various, so it is difficult to standardization of the work conditions. Therefore, the work conditions are depended on the workers of experience and skill. In the plastic extrusion process, it has five control heating points on the cylinder and three control heating points on the die. In addition, there is one control point on the extrusion process. It is extrusion speed. In this case, we don't know how these affect product quality. We structure the multiple linear regression equation with the temperature of cylinders and dies as independent variables and the product weight as dependent variable. We solve this equation using statistic computer package named Juse-Qcas.