• The KSFM Journal of Fluid Machinery
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• v.18 no.3
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• pp.5-11
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• 2015

Ocean waves have huge amounts of energy, even larger than wind or solar, which can be extracted by some mechanical device. This can be done by creating a system of reacting forces, in which two or more bodies move relative to each other, while at least one body interacts with the waves. This moves the floater up and down. The floaters are connected to an arm structure, which are mounted on a fixed hull structure. Hence, the structure of the floater is very important. A static structural analysis with FSI (Fluid-Structure Interaction) analysis is conducted. To achieve the pressure load for the FSI analysis, the floater is simulated on a wave generator using rigid body motion. The structural analysis is done to examine the stresses on the whole system, and four types of flange and floater are optimized. The result shows that the structure of floater with wood support is the safest.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.4
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• pp.501-509
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• 2010

A floating crane is a crane-mounted ship and is used to assemble or to transport heavy blocks in shipyards. In this paper, the static and dynamic response of a floating crane and a heavy block that are connected using elastic booms and wire ropes are described. The static and dynamic equations of surge, pitch, and heave for the system are derived on the basis of flexible multibody system dynamics. The equations of motion are fully coupled and highly nonlinear since they involve nonlinear mass matrices, elastic stiffness matrices, quadratic velocity vectors, and generalized external forces. A floating frame of reference and nodal coordinates are employed to model the boom as a flexible body. The nonlinear hydrostatic force, linear hydrodynamic force, wire-rope force, and mooring force are considered as the external forces. For numerical analysis, the Hilber-Hughes-Taylor method for implicit integration is used. The dynamic responses of the cargo are analyzed with respect to the results obtained by static and numerical analyses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.729-734
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• 2017

A safety relief valve is a device that relieves excessive pressure in piping lines or tanks and maintains pressure at the appropriate pressure level for use. The (pressure in the) safety valve is directly influenced by the change in the back pressure, depending on whether the vents in the spring bonnet are vented to the atmosphere or to the outlet. The back pressure is divided into the built-up back pressure and the superimposed back pressure, and the back pressure characteristics vary according to the usage conditions. The safety valve used in this study is a Conventional Safety Relief Valve. The blowdown of the safety valve is predicted by establishing the equilibrium equation between the opening force and spring force considering the back pressure characteristics. Its reliability is secured by using CFX17.1. In addition, the safety of the safety valve trim was examined through fluid-structure interaction analysis.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.1
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• pp.33-40
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• 2013

Since most of yacht sails are made of thin fabric, they form cambered sail shape that can efficiently generate lift power by aerodynamic interaction and by external force delivered from supporting structures such as mast and boom. When the incident flow and external force alter in terms of volume or condition, the shape of sail also change. This deformation in shape has impact on the peripheral flow and aerodynamic interaction of the sail, and thus it is related to the deformation of the sail in shape again. Therefore, the precise optimization of aerodynamic performance of sail requires fluid-structure interaction (FSI) analysis. In this study, the simplified sail without camber was under experiment for one-way FSI that uses the result of flow analysis to the structural analysis as load condition in an attempt to fluid-structure interaction phenomenon. To confirm the validity of the analytical methods and the reliability of numerical computation, the difference in deformation by the number of finite element was compared. This study reproduced the boundary conditions that sail could have by rigs such as mast and boom and looked into the deformation of sail. Sail has non-linear deformation such as wrinkles because it is made of a thin fabric material. Thus non-linear structural analysis was conducted and the results were compared with those of analysis on elastic material.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.324-332
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• 2018

It is known that damages to the subsea cables used for electric power transmission between islands and countries, including renewable energy from offshore wind power, current, tides, etc., cost much to restore, which causes social and economic losses. Various types of fishing rigs and anchors have been reported to be the greatest hazards to subsea cables. It is possible to design and construct a suitable protection facility for a subsea cable by precisely estimating the underwater behavior of such hazardous apparatuses. In this study, numerical simulations of the underwater behaviors of various hazardous apparatuses were carried out using fluid-structure interaction (FSI) analysis as a basic study to simulate the actual behavior phenomena of hazardous apparatuses in relation to a subsea cable. In addition, the underwater drop characteristics according to the types of hazardous apparatuses were compared. In order to verify the accuracy of the FSI analysis method used in this study, we compared the test results for underwater drops of a steel ball bearing. Stock anchors, stockless anchors, and rocket piles, which were actually reported to be the cases of damage to subsea cables along the southwest coast of Korea, were considered as the hazardous apparatuses for the numerical simulations. Each hazardous apparatus was generated by a Lagrangian model and coupled with the fluid domain idealized by the Eulerian equation to construct the three-dimensional FSI analysis model. The accuracy of the numerical simulation results was verified by comparing them with the analytical solutions, and the underwater drop characteristics according to the types of hazard apparatuses were compared.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.24-35
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• 2018

Impeller blades in the centrifugal compressor are subjected to periodic aerodynamic excitations by interactions between the impeller and the diffuser vanes (DV) in resonant conditions. This may cause high cycle fatigue (HCF) and eventually result in failure of the blades. In order to predict the structural response accurately, the aerodynamic excitation and the major resonant conditions were predicted using unsteady computational fluid dynamics (CFD) and structural analysis. Then, a forced vibration analysis was performed by going through one-way fluid-structure interaction (FSI). A numerical analysis procedure was established to evaluate the structural safety with respect to HCF. The numerical analysis procedure proposed in this paper is expected to contribute toward preventing HCF problems in the initial design stage of an impeller.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.3
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• pp.185-195
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• 2021

The flapping-wing micro air vehicle (FW-MAV) in this study utilizes the cambered wings made of quite flexible material. Similar to the flying creatures, the present cambered wing uses three different materials at its leading edge, vein, and membrane. And it is constrained in various conditions. Since passive rotation uses the flexible nature of the wing, it is important to select an appropriate material for a wing. A three-dimensional fluid-structure interaction solver is developed for a realistic modeling of the cambered wing. Then a parametric study is conducted to evaluate the aerodynamic performance in terms of the elastic modulus of leading edge and vein. Consequently, the elastic modulus plays a key role in enhancing the aerodynamic performance of FW-MAVs.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.627-635
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• 2021

The fire damage and structural performance of a steel-concrete composite superstructure under a highway bridge exposed to fire loading was evaluated. To enhance the accuracy and efficiency of the numerical analysis, a proposed fluid-structure interaction fire analysis method was implemented in Ansys Fluent and Ansys Mechanical. The temperature distribution and performance evaluation of the steel-concrete composite superstructure according to the vertical distance from the fire source to the bottom flange were evaluated using the proposed analysis method. From the analysis, the temperature of the concrete slab and the bottom flange of the steel-concrete composite superstructure exceeded the critical temperature. Also, when the vertical distance from the fire source was 13 m or greater, the fire damage of the steel-concrete composite superstructure was found to within a safe limit.

• Journal of Navigation and Port Research
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• v.44 no.3
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• pp.264-274
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• 2020

The Ro-Ro ferry ship capsized and sank to the bottom of the sea because of the rapid turning for several reasons, such as lack of stability due to the center of gravity rise from the extension and rebuilding of the stern cabin, excessive cargo loading, and shortage ballast, poor lashing, etc. The purpose of this study was to investigate and analyze the cause of the ship's rapid flooding, capsizing, and sinking accident according to rapid turning scientifically and accurately using the Fluid-Structure Interaction( FSI) analysis technique. Several tests were conducted for this cause investigation of the flooding and sinking accident correctly and objectively, such as the realization of the accurate ship posture tracks according to the accident time using several accident movies and photos, the validation of cargo moving track, and sea water inflow amount through the exterior openings and interior paths compared with the ship's posture according to the accident time using the floating simulation and hydrostatic characteristics program calculation, and the performance of a full-scale ship flooding·sinking simulation.

• Korean Journal of Computational Design and Engineering
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• v.21 no.1
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• pp.90-98
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• 2016

When ships and offshore plants are flooded or the floating crane is equipped with a heavy object, these floating structures are excessively inclined. In this case, immersion, heel, and trim affecting the hydrostatic restoration performance are very large and are coupled each other. In this paper, in order to calculate a static equilibrium position of floating structures with excessive inclination, the nonlinear governing equations were constructed by sequential linearization. In the governing equation, the immersion, heel, and trim are fully coupled, and the equations are represented using a plane area, a primary moment, and a moment of inertia of the water plane area. Therefore, it is possible to calculate the additional factor related the water plane area for estimating stability. Position and orientation of the floating structure are obtained by iterative calculation. The calculated results are compared with the previous studies in the aspect to the performance and the accuracy.