• 한국해안해양공학회지
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• 제4권2호
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• pp.72-82
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• 1992

현지 해안에서 발생하는 해빈류를 정확히 예측하기 위해서는, 해빈류의 기인력인 다방향불 규칙파낭에 의해서 발생하는 방사응력(radiation stress)에 대해서 충분히 파악해 둘 필요가 있다. 본 연구에서는, 이차원수리실험에 있어서 단일성분파, 이성분합성 파, Bretschneider-광역형의 불규칙파를 발생시켜서, 그들의 천수쇄파변형에 따른 전파특성에 대해서 고찰하고, 불규칙파의 천수쇄파변형을 해석할 경우 가정되어지는 3가지 방법, 즉 (1) 파별해석법, (2) 성분파법, (3) 대표파법의 적용성에 대해서 檢討했다. 파별해석법에 대해서는, zero-down cross 법에 의해, 파별해석되어진 불규칙파의 전파특성으로서, 통계파(최대파, 1/3유의파, rms파 등) 및 시계열중의 임의 특정의 개개파의 파고 및 주기의 천수변화라고 하는 관점으로부터 검토했다. 또한, 성분파법에 대해서는 Spectrum 해석에 의해, 입력신호인 기본주파수성분파 및 천수비파변형에 따라 증가하는 간섭주파수 성분파에 대한 파속 및 파고의 천수변형이라고 하는 관점으로부터 그 타당성에 대해서 검토했다.

• 대한조선학회논문집
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• 제60권5호
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• pp.341-350
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• 2023

In this paper, numerical experiments are performed to examine the collision between a solitary wave and a wave-packet (dispersive wave) in shallow water. We attempt to introduce the improved Boussinesq equation governing the experiments, which is solved by using a semi-analytical approach, called Pseudo-parameter Iteration method(PIM). Using various numerical experiments, we have observed that the wave-packet (propagating dispersive wave) experiences a phase shift after collision with a solitary wave. This phenomenon may be considered as a nonlinear wave-wave interaction in shallow water.

• 한국해양공학회지
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• 제15권3호
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• pp.114-119
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• 2001

Goda formula (Goda, 1973) has been used in the determination of wave pressures acting on a large size caisson such as the pier of the cable stayed bridge at sea. Goda formula, however, is to evaluate the wave pressures acting the infinite vertical caisson of composite breakwater so that it can`t be applied to a large caisson with finite width and length because of diffraction effects. In the present study, three dimensional nonlinear frequence domain method based on perturbation method and boundary integral method is applied to the computation of the linear and nonlinear wave pressures acting on the front of a large size caisson under the variation of its width and length, and angle of incident wave. The numerical results are compared to Goda\`s ones, and then the characteristics of wave pressure distributions acting on a large size caisson are discussed.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• 제4권1호
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• pp.22-30
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• 2001

A new concept wave absorber is proposed. It is a net type wave absorber. Its efficiency was reported in another publication. Since it is based on new concept, the traditional wave absorber theory is not applicable. It is modeled by introducing damping terms in linearized free surface boundary conditions in this study. The length and the thickness of the wave absorber are modeled by the length and the coefficient of the damping terms. Series of experiments are carried out to get the data for the coefficients of the damping term. The boundary element method is adopted to solve the system. The predicted wave heights show excellent agreement with those of experiments when the lengths of the incoming waves are within the length of the wave absorber.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.209-218
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• 2009

In this study, properties of shear wave velocity of core zone in filldams are analyzed. Shear wave velocity is derived using analysis of surface wave method that can be used nondestructively on the surface of filldams. These values are acquired through the tests for the core zone of six filldams by SASW and HWAW methods. Existing 2 more results are added. Shear wave velocity according to the depth and confining pressure are estimated, respectively. These analytical results are compared with the frequently used empirical method by Sawada and Takahashi.

• 한국해양공학회지
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• 제23권4호
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• pp.6-11
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• 2009

In this study, the internal waves in two-density layered fluids were analyzed using the Numerical Wave Tank (NWT) technique in the frequency domain. The NWT is based on a two-domain Boundary Element Method with the potential fluids using the whole-domain matrix scheme. From the mathematical solution of the two-domain boundary integral equation, two different wave modes could be classified: a surface wave mode and an internal wave mode, and each mode were shown to have a wave number determined by a respective dispersion relation. The magnitudes of the internal waves against surface waves were investigated for various fluid densities and water depths. The calculated results are compared with available theoretical data.

• 한국지반공학회논문집
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• 제20권1호
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• pp.61-73
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• 2004

레일레이파와 러브파는 탄성파 중에서 표면파에 속하는 것으로, 매우 중요한 표면파로 인식되고 있다. 러브파의 파동 전파시 매질내에 발생되는 변형은 SH파와 같은 전단형태이므로, 러브파는 P-파에 의해 교란되지 않는 특성이 있다. 이러한 특성으로 인하여 러브파가 레일레이파나 다른 체적파보다 더 유용한 탄성파로 인식되고 있다. 본 연구에서는 표면파를 활용하는 대표적 실험기법인 SASW 기법에서 러브파를 도입하고자 하는 목적으루 이론적, 수치해석적, 실험적 방법으로 러브파의 위상속도 분산 특성을 연구하였다. 특히, 러브파의 수평성분과 레일레이파의 수직 수평 성분의 특성을 연구하기 위하여, 반무한 지반, 2층 구조의 지반에 대하여 2차원,3차원 유한요소 해석을 수행하였다. 또한, 수치해석으로 획득한 러브파와 레일레이파에 대한 결과를 확인하기 위하여 일반 지반에서 현장실험을 수행하였다. 이와 같은 수치해석과 현장실험을 통하여 러브파의 위상속도 분산특성이 SASW 기법의 정확성과 신뢰성을 더욱 향상시키기 위한 추가 자료로 매우 유용할 것이라는 것을 확인하였다.

• 대한조선학회논문집
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• 제52권3호
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• pp.222-235
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• 2015

The purpose of this study is to suggest guidelines for riser fatigue analysis in terms of selection of reasonable analysis method. Three analysis methods (spectral, regular wave, rain-flow counting) are introduced and compared. As the riser systems give non-linear response, the time-domain analysis method is more preferred than frequency-domain analysis method. The spectral fatigue analysis method, however, is still useful for identifying fatigue prone areas. Once stress RAO is established, fatigue damage can be calculated very quickly. The regular wave method and the rain-flow counting method are more time consuming but give more exact results compare to spectral method. In case of regular wave method, a set of regular waves which represent random sea states is considered for dynamic analysis. The rain-flow counting method is the most intuitive and exact method because it refers time history stresses containing most of non-linear effects of the riser system. However, it is not common for early design stage to use rain-flow counting method because of its high cost. In this study, it was confirmed that the regular wave method is the most cost effective way in specific cases. However, if the system is highly non-linear, it seems that the regular wave method gives less accurate results than rain-flow counting method. Therefore, it is imperative that the engineers select appropriate analysis method based on design stage and given engineering period. This paper also discusses the theoretical background of each calculation method and hydrodynamic aspects of marine riser systems. A steel catenary riser (SCR) line on FPSO was considered and marine dynamic program (OrcaFlex) was used for static and dynamic analysis.

• 한국지반공학회논문집
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• 제20권6호
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• pp.51-59
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• 2004

공학적 물성치로서의 저변형율에서의 전단탄성계수의 결정은 다양한 토목분야에서 매우 중요하다. 본 논문에서는 저변형율에서의 전단탄성계수를 결정하기 위하여 개발된 HWAW(Harmonic Wavelet Analysis of Wave)방법을 이용한 지반조사기법의 실제 현장에서의 타당성을 검증하기 위하여 두 곳의 현장에 HWAW방법을 적용하였다. HWAW방법을 검증하기 위하여 동일한 현장에서 수행된 SASW시험과 PS-Suspension Logging 실험의 결과와 비교하였다. 이를 통하여 HWAW방법이 배경잡음과 지반의 횡방향 불균일성에 의한 오류를 기존 방법에 비하여 최소화 할 수 있으며, 국부적이며 정밀한 대상지반의 실제 전단파 속도 주상도를 매우 효과적으로 결정할 수 있음을 확인할 수 있었다.

• 한국소음진동공학회논문집
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• 제17권2호
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• pp.121-129
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• 2007

There has been much effort to find suitable methods for structural analysis in the mid-frequency region where traditional low frequency methods have increasing uncertainties whilst statistical energy analysis is not strictly applicable. Systems consisting of relatively stiff beams coupled to flexible plates have a particularly broad mid-frequency region where the beams support only a few modes whilst the plate has a high modal density and modal overlap. A system of two parallel beams coupled to a plate is investigated based on the wave method, which is an approximate method. Muller's method is utilised for obtaining complex roots of a dispersion wave equation, which does not converge in the conventional wave method based on a simple iteration. The wave model is extended from a single-beam-plate system, to a plate with two identical beams which is modelled using a symmetric-antisymmetric technique. The important hypothesis that the coupled beam wavenumber is sufficiently smaller than the plate free wavenumber is experimentally verified. Finally, experimental results such as powers and energy ratios show the validity of the analytical wave models.