• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.267-274
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• 2018

A variety of appendages are attached to coastal and offshore fishing boats to improve stability during navigation or fishing operations (stability performance and roll reduction). These appendages are generally classified into three types, which are shown in Fig. 1. The numerical calculations were conducted for the following eight cases: one case of a bare hull, three cases where a single appendage attached, three cases of a pair of appendages attached, and one case where all three appendages were attached. Table 1 presents the main dimensions of the bare hull and Table 2 describes the main dimensions of the three appendages. The fluid dynamic performance with regard to the three hull appendages was evaluated via CFD for the following cases: each of the appendages attached independently, a pair of appendages attached, and all three appendages attached simultaneously. The No. 1 appendage showed that pressure resistance was proportionally greater than friction resistances. Both Nos. 2 and 3 appendages showed comparable levels of pressure and friction resistances. The correlation between appendages was minimal in the case of pairs and Comparing the cases of the No. 2 appendage attached and all appendages attached, at 11 kn, the EHP showed an difference of 9 %.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.2
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• pp.83-98
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• 2000

자오방향 및 주변방향으로 피르스트레스트 하중이 작용된 축대칭 쉘 구조물을 기하학적으로 축대칭인 구조물의 특성을 최대한으로 이용할 수 있도록 회전 링요소로 모델화하였다 보강링 요소의 모델은 축대칭 쉘요소를 이용하였으며 본체 구조물과 절점에서 부착되있는 것으로 가정하여 이의 편심을 고려하였다 유체-구조물의 상호관계는 접촉면에서 구조물의 가속도에 비례한 부가질량으로 표현하였으며 부가질량은 유체를 비점성 비압축 및 비회전을 가정하여 유한요소법에 의해 구하였다 이에 대한 수치해석을 통하여 고유진동해석 및 지진하중을 주하중으로 한 동적해석을 실시하였다 프로그램을 통하여 해석한 결과를 프리스트레스 하중 하에서 고유진동수에 대한 정해와 비교한 결과 20개의 요소로 모델링한 경우에서도 정해와 근접한 해를 얻을 수 있었다 또한 내부유체가 있는 경우와 링보강을 한 경우에 대한 고유진동수를 문헌과 비교한 결과 근접한 해를 얻을 수 있었다.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.5
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• pp.25-33
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• 2001

For the seismic design and analysis of LMR(liquid metal reactor) being developed in Korea, it is necessary to develop the simple seismic analysis model including the fluid-structure interaction effects. In this paper, the theoretical backgrounds for the fluid added mass of the immersed concentric cylinders are investigated and the seismic analysis code using the Runge-Kutta algorithm, which can consider the fluid added mass matrix in system matrix, are developed to perform the time history seismic analysis. Form the coupled modal analysis and the seismic analysis for the simple immersed concentric cylinders, it is verified that the fluid added mass significantly affect the vibration characteristics and the seismic responses. Therefore the fluid coupled effects should be carefully considered in seismic response analysis of the immersed concentric cylinders.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.271-281
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• 2005

The effects of radiation damping is used to compensate the truncated boundary which is relatively close to the structure-fluid interface in the fluid element surrounding the submerged structures. An efficient ring element is presented to model the shell and fluid element which fully utilizes the characteristics of the axisymmetry. The computational model uses the technique which separate the meridional shape and circumferential wave mode and gets similar result with the exact solution in the eigenvalues and the earthquake analysis. The fluid-structure interaction techniques is developed in the finite element analysis of two dimensional problems using the relations between pressure, nodal unknown acceleration and added mass assuming the fluid to be invicid, incompressible and irrotational. The effectiveness and efficiency of the technique is demonstrated by analyzing the free vibration and seismic analysis using the added mass matrix considering the structural deformation effect.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.4
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• pp.71-82
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• 1999

An axisymmetric shell element which includes the effects of the meridional and circumferential cable prestresses is developed. The fluid-structure interaction is expressed as added mass effect which is in proportion to the acceleration of the structure in interface surface. The added mass is obtained by using finite element method under the assumption that the fluid is invicid, incompressible and irrotational. It is coded for personal computer by the maximum use of axisymmetic properties and the dynamic analysis are performed under seismic exitations. A ring element makes the characteristics of the axisymmetric shell to be fully utilized. The elgenvalue solutons under the initial prestresses and the internal fluid are well agreed with the exact solutions and references by using under 20 elements. The eigenvalues are decreased along the increasing the height of internal fluid and these effects are dominant under the lower wave numbers. The results of the seismic analysis show that the radial deflection under the meridional prestress is a little larger than that under the circumferential prestress.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.3
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• pp.351-360
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• 2000

A simple numerical modelling technique is proposed for estimating the shear lag effects of framed-tube system with multiple internal tubes. The tube(s)-in-tube structure is analysed by using an analogy approach in which each tube is individually modelled by a beam that can accounts for the flexural and shear deformations, as well as the shear lag effects. The numerical analysis is based on the minimum potential energy principle in conjunction with the variational approach. The shear lag phenomenon of such structures is studied with additional bending stresses. Structural parameters governing the shear lag behaviour in tube(s)-in-tube structures are also investigated through thirty-three numerical examples.

• Journal of the Korean Geographical Society
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• v.44 no.3
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• pp.395-409
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• 2009

The objective of this paper is to illustrate that kriging can provide an effective framework both for integrating remote sensing data and for uncertainty modeling through a case study of sediment grain size mapping with remote sensing data. Landsat TM data which show reasonable relationships with grain size values are used as secondary information for sediment grain size mapping near the eastern part of Anmyeondo and Cheonsuman bay. The case study results showed that uncertainty attached to prediction at unsampled locations was significantly reduced by integrating remote sensing data through the analysis of conditional variance from conditional cumulative distribution functions. It is expected that the kriging-based approach presented in this paper would be efficient integration and analysis methodologies for any environmental thematic mapping using secondary information as well as sediment grain size mapping.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.688-693
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• 2016

This paper describes the parachute dynamics modeling and simulation results for the development of training simulator of a HALO (High Altitude Low Opening) parachute, which is currently in use for military purposes. The target parachute is a rectangular shaped parafoil and its dynamic model is derived based on the real geometry data as the 9-DOF nonlinear equations of dynamics. The simulation was conducted through the moment of inertia and its aerodynamic derivatives to reflect the real characteristics based on the MATLAB/Simulink. In particular, its modeling includes the typical characteristics of the added mass and moment of inertia, which is shown in the strong effects in Lighter-Than-Air(LTA) flight vehicle. The proposed dynamic modeling was evaluated through the simulation under the spiral turning flight conditions of the asymmetric control inputs and compared with the performance index in the target parachute manual.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.3
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• pp.190-196
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• 2005

The ratio between the hydrodynamic force produced by a submarine tau appendage and that acting on an equivalent appendage in isolation is regarded as tail plane efficiency. It is an important parameter in numerical simulations because it has a significant effect on predicted stability, controllability, and maneuverability. The paper introduces some recent work to improve the reliability and general applicability of current methods of tail plane efficiency estimation.

• Proceedings of the KSRS Conference
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• 2000.04a
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• pp.143-148
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• 2000

레이저 프로파일링 시스템의 등장으로, 기존에는 얻을 수 없었던 도시 지역에 대한 DTM 취득이 가능해졌고, 더욱 정확한 정사투영영상 또한 제작할 수 있게 되었다. 하지만, 높이 변화를 보이는 자연지물과 인공구조물이 있는 지역에 대해 기존의 정사투영사진 제작기법이 적용될 때, 폐색이나 이중매핑과 같은 문제가 발생하게 된다. 특히 고층건물이 밀집되어 있는 도심지에서 이러한 현상은 두드러져 정사투영영상의 품질을 저해하는 주요한 원인이 된다. 따라서, 본 연구에서는 카메라의 외부표정요소와 DTM을 이용하여 폐색영역을 탐지하고, 폐색이 안된 다른 영상의 정보를 통해 폐색영역을 복원하여 더욱 완전한 정사투영을 제작할 수 있는 알고리즘을 제안하였다. 제안된 알고리즘에 의해 자연지물이나 인공고조물에 의한 폐색영역을 탐지할 수 있었고 폐색영역의 많은 부분을 부가영상을 이용하여 복원하였다. 건물에 대한 사전지식을 이용하여 폐색영역을 탐지하는 국내 연구가 있지만, 본 연구는 건물에 대한 부가정보나 모델링을 사용하지 않고 DTM과 카메라 외부표정요소만을 이용하여 폐색영역을 탐지한다는 점에서 이러한 연구들과 차별성을 가진다.