• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.292-299
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• 1999

In order to investigate dynamic behaviors of marine cables under wave and earthquake forces a geometric nonlinear. F, E formulation of marine cables is presented and tangent stiffness and mass matrices for the isoparametric cable element are derived, The initial equilibrium state of cables subjected to self -weights and current forces is determined and free vibration and dynamic nonlinear analysis of cable structures under additional environmental loads are performed based on the initial configuration Challenging examples are presented and discussed in order to demonstrate the feasibility of the present finite element method and investigate dynamic nonlinear behaviors of marine cables.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.6
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• pp.624-640
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• 2017

In this paper, the slamming coefficients on local members of a jacket structure under plunging breaker are studied based on numerical simulations. A 3D numerical model is used to investigate breaking wave forces on the local members of the jacket structure. A wide range of breaking wave conditions is considered in order to get generalized slamming coefficients on the jacket structure. In order to make quantitative comparison between CFD model and experimental data, Empirical Mode Decomposition (EMD) is employed for obtaining net breaking wave forces from the measured response, and the filtered results are compared with the computed results in order to confirm the accuracy of the numerical model. Based on the validated results, the slamming coefficients on the local members (front and back vertical members, front and back inclined members, and side inclined members) are estimated. The distribution of the slamming coefficients on local members is also discussed.

• Journal of Ocean Engineering and Technology
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• v.18 no.3
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• pp.13-19
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• 2004

The structural behavior of a worn tire, attached to carbon fiber steel pile by current and wave forces, has been investigated through the numerical method. The finite element model has been developed, by considering that the composite material of rubber and cord is orthotropic, the rubber is isotropic, and that all the material behaves as linear elastic. The pressure distribution by wave and current, around the worn tire, has been estimated through the adjustment for the concept of flow separation. Also, the structural behavior of the worn tire has been examined, by comparing the situation wherein the space between the pile is reinforced, and tire as elastic and isotropic material, with the one left empty. Through this comparison, it is determined that the space between pile and tire has to be filled with elastic and isotropic material, in order to avoid the failure by wave and current action.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.06a
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• pp.273-274
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• 2013

Recently, as offshore wind towers are developed, the size of wind towers have become larger and larger, and offshore wind towers are exposed to various external forces such as wave and current compared with onshore wind towers. Thus, the stability of offshore wind towers is more required than onshore wind towers. In this study, when the wind celerity of 60m/s blows to the cylinder, cone, and stair typed towers, the wind and wave forces on foundation are calculated by p-y relation.

• Structural Engineering and Mechanics
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• v.6 no.3
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• pp.347-362
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• 1998

In this study an improved design method for the traditional A-type(or V-type) offshore template platform system was proposed to mitigate the vibration induced by the marine environmental loadings and the strong ground motions of earthquakes. A newly developed material model was combined into the structural system and then a nonlinear dynamic analysis in the time domain was carried out. The analysis was focused on the displacement and rotation induced by the input wave forces and ground motions, and the mitigation effect for these responses was evaluated when the viscoelastic damping devices were applied. The wave forces exerted on the offshore structures are based on Stokes fifth-order wave theory and Morison equation for small body. A step by step integration method was modified and used in the nonlinear analysis. It was found that the new design approach enhanced with viscoelastic dampers was efficient on the vibration mitigation for the structural system subjected to both the wave motion and the strong ground motion.

• Structural Engineering and Mechanics
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• v.68 no.6
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• pp.701-711
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• 2018

Herein, the thermo-magneto-elastic wave dispersion answers of functionally graded (FG) double-nanobeam systems (DNBSs) are surveyed implementing a nonlocal strain gradient theory (NSGT). The kinematic relations are derived employing the classical beam theory. Also, scale influences are covered precisely in the framework of NSGT. Moreover, Mori-Tanaka homogenization model is introduced in order to obtain the effective material properties of FG nanobeams. Meanwhile, effects of external forces such as thermal and Lorentz forces are included in this research. Also, based upon the Hamilton's principle, the Euler-Lagrange equations are developed; afterwards, these equations are incorporated with those of NSGT to reach the nonlocal governing equations of FG-DNBSs. Furthermore, according to an analytical approach, the governing equations are solved to obtain the wave frequencies and phase velocities of FG-DNBSs. At the end, some illustrations are rendered to clarify the influences of a wide range of involved parameters.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.2
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• pp.38-50
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• 1998

In order to understand the characteristics of floating breakwaters we planned series of experimental and numerical investigations and completed the first stage which is the experiment with fred pontoons near the free surface. As controlling parameters the draft and breadth of pontoon were varied and the wave frequency and steepness were also varied. Wave transmission and forces exiled on the breakwater were experimentally investigated and compared with the results computed based on linear potential theory. Discussions made are on the effect of draft and wave length on the wave transmission and force in fixed pontoon case. The predicted and measured results show quantitatively good agreement both in forces and transmission coefficient. The effect of separation distance between two pontoons on the wave transmission and force in array case is also examined.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.711-722
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• 2008

A projectile when passes through a moving shock wave, experiences drastic changes in the aerodynamic forces as it moves from a high-pressure region to a low pressure region. These sudden changes in the forces are attributed to the wave structures produced by the projectile-flow field interaction, and are responsible for destabilizing the trajectory of the projectile. These flow fields are usually encountered in the vicinity of the launch tube exit of a ballistic range facility, thrusters, retro-rocket firings, silo injections, missile firing ballistics, etc. In earlier works, projectile was assumed in a steady flow field when the computations start and the blast wave maintains a constant strength. However, in real situations, the projectile produces transient effects in the flow field which have a deterministic effect on the overtaking process. In the present work, the overtaking problem encountered in the near-field of muzzle guns is investigated for several projectile Mach numbers. Computations have been carried out using a chimera mesh scheme. The results show that, the unsteady wave structures are completely different from that of the steady flow field where the blast wave maintains a constant strength, and the supersonic and subsonic overtaking conditions cannot be distinguished by identifying the projectile bow shock wave only.

• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.16-22
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• 2010

In this paper, the diffraction problems for fixed offshore structures are solved using a hybrid scheme. In this hybrid scheme, potential-based solutions and the Navier-Stokes-based finite volume method (FVM) with a volume-of-fluid (VOF) method are combined. We introduce a buffer zone for efficient wave-making and damping. In this buffer zone, the near field solution from FVM-VOF is gradually changed to Stokes' 2nd order wave solutions. Three different models, including the truncated cylinder, sphere, and wigleyIII model, are numerically investigated in regular waves with a wave steepness of 1/30. The efficiency and accuracy of the hybrid scheme are numerically validated from results using different domain sizes and buffer zones. The wave exciting forces from the FVM-VOF simulations are compared with experiments and potential-based solutions from the higher-order boundary element method (HOBEM). This comparison shows good agreement between the hybrid scheme and potential-based solutions.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.395-402
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• 2019

In order to increse the stability of old caissons, the design and the construction are performed by installation of new caissons on the back of or on the front of old caissons. In this study, we use the eigenfunction expasnion method to analyze the characteristics of wave forces when new circular caissons are installed on the back of old caissons. The comparison of numerical results between eigenfunction expansion method and ANSYS AQWA is made and the wave force acting on each circular caisson is calculated by considering the wave-structure interaction effect.