• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.377-384
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• 2022

Vortex-induced vibration (VIV) occurs owing to the vortex generated from the back side of the appendages of ships and submarines during operation. Recently, the importance of high-order modes (HOMs) vibration and fatigue failure has become increasingly emphasized by increasing the speed of ships and the size of structures. In addition, predicting the vibration of HOMs is significantly necessary as the VIV becomes stronger in the fast flow speed condition than in the low flow speed condition. This study introduces a methodology according to HOMs hybrid Fluid Structure Interaction (FSI) for predicting the HOMs VIV on the hydrofoils. The HOMs FSI system is verified by comparing the VIV results from the FSI simulation with the experimental results. Finally, the effectiveness of the HOMs FSI is determined by applying the maximum von-Mises stress obtained from the VIV on the hydrofoil to the S-N curve released from Det Norske Veritas (DNV). VIV results from the HOMs FSI include the lock-in characteristics as well as a significant increase of more than 10 times compared with that of low-order modes (LOMs) FSI. In the future works, advanced studies will be required for improving cantilever boundary conditions and the shape of hydrofoils.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.68-74
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• 2011

Recently, thanks to the advanced computational power and numerical methods, it is made possible to analyze the flow around moving bodies using computational fluid dynamics techniques. In those simulations, moving mesh techniques should be able to represent both the body motion and boundary deformation, which are frequently encountered in fluid-structure interaction and/or six degree-of-freedom problems. In the present study, the staggered loosely coupling algorithm was used for fluid-structure interaction and the Laplacian operator based technique was used for moving mesh. For the verification of the developed computational method, the flow around a two-dimensional cylinder was simulated and analyzed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.125-132
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• 2019

Because the water exposed to shock waves caused by an underwater explosion cannot withstand the appreciable tension induced by the change in both pressure and velocity, the surrounding water is cavitated. This cavitating water changes the transferring circumstance of the shock loading. Three phenomena contribute to hull-plate damage; initial shock loading and its interaction with the hull plate, local cavitation, and local cavitation closure then shock reloading. Because the main concern of this paper is local cavitation due to a near-field underwater explosion, the water surface and the waves reflected from the sea bottom were not considered. A set of governing equations for the structure and the fluid were derived. A simple one-dimensional infinite plate problem was considered to verify this uncoupled solution approach compared with the analytic solution, which is well known in this area of interest. The uncoupled solution approach herein would be useful for obtaining a relatively high level of accuracy despite its simplicity and high computational efficiency compared to the conventional coupled method. This paper will help improve the understanding of fluid-structure interaction phenomena and provide a schematic explanation of the practical problem.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.10a
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• pp.140-141
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• 2014

최근 대용량 고속 컴퓨터의 출현과 고도 비선형 동적 해석 소프트웨어가 개발됨에 따라 안전사고 규명와 안전설계 등에 고도 정밀 Modeling & Simulation(M&S) 시스템이 널리 적용되고 있다. 특히 해양안전은 천배의 밀도를 갖는 해양에서의 내충돌 및 내충격 응답을 실선규모로 규명 분석하여야 할 것이다. 이를 위해서는 고도 정밀 M&S 시스템에 유체-구조 연성(Fluid-Structure Interaction, FSI) 해석기법을 적용하여야 보다 정확하고 합리적인 안전성을 평가할 수 있다. 여기서는 이러한 고도 정밀 M&S 시스템을 적용한 해양안전기술의 적용 분야를 소개하고자 한다.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.560-564
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• 2008

풍력발전에 사용하는 풍력터빈의 블레이드의 적어도 20년 이상의 설계수명이 요구된단. 블레이드는 바람에 의한 압력, 지지대 구조에 의해서 가해지는 힘과 모멘트에 의해 블레이드에 변형이 가해진다. 특히 바람에 의해 블레이드는 연속적인 하중을 받아서 재료를 손상시킨다. 본 연구에서는 블레이드와 허브로 구성된 모델을 이용하여, 전산유체해석을 일차적으로 수행하여 블레이드 주변의 압력분포를 구하였다. 계산된 압력을 이용하여 다음 단계로 유한요소해석을 수행하여 블레이드 재료에 발생하는 응력을 계산하여 피로해석을 수행하였다. 피로해석을 통해 재료에 미치는 손상률을 구하였다. 다양한 블레이드 피치 각도과 바람의 속도에 따라 해석결과를 비료 분석하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1575-1580
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• 2010

Recently, the development of bio-mimetic underwater vehicles that can emulate the characteristic movements of marine fish and mammals has attracted considerable attention. In this study, the motion of the batoid (i.e., cownose ray) fin that facilitates excellent cruising and maneuvering during underwater movement has been studied. The velocity achieved and distance covered with each fin movement are numerically studied. A fluid-structure interaction method is used to perform 3D time-dependent numerical analysis, wherein an adaptive mesh is employed to account for the large deformation of a fin interacting with a fluid. The results of a preliminary study show that the thrust of a ray fin is highly dependent on the frequency. Further, once the fin amplitude required for generating a given thrust is evaluated for the conditions experienced by an actual ray, the frequency and amplitude values for achieving better thrust are determined.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.461-462
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• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.523-524
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• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.269-270
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• 2010

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.6
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• pp.357-363
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• 2016

In this study, we perform a series of aero-thermo-mechanical analyses to predict the running-tip clearance and the effects of impeller deformation on the performance using a centrifugal compressor. During operation, the impeller deformation due to a combination of the centrifugal force, aerodynamic pressure and the thermal load results in a non-uniform tip clearance profile. For the prediction, we employ the one-way fluid-structure interaction (FSI) method using CFX 14.5 and ANSYS. The predicted running tip clearance shows a non-uniform profile over the entire flow passage. In particular, a significant reduction of the tip clearance height occurred at the leading and trailing edges of the impeller. Because of the reduction of the tip clearance, the tip leakage flow decreased by 19.4%. In addition, the polytrophic efficiency under operating conditions increased by 0.72%. These findings confirm that the prediction of the running tip clearance and its impact on compressor performance is an important area that requires further investigation.