• 충청수학회지
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• 제35권2호
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• pp.137-147
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• 2022

In this paper, we considered the Dirichlet initial boundary value problem of a nonlinear viscoelastic wave equation with nonlinear damping and source terms, and investigated finite time blow-up phenomena of the solutions to the equation with arbitrary positive initial data, under suitable conditions.

• Earthquakes and Structures
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• 제13권5호
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• pp.465-471
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• 2017

This work derives a generalized time fractional differential equation governing wave propagation in a radially vibrating non-classical cylindrical medium. The cylinder is made of a transversely isotropic hyperelastic John's material which obeys frequency-dependent power law attenuation. Employing the definition of the conformable fractional derivative, the solution of the obtained generalized time fractional wave equation is expressed in terms of product of Bessel functions in spatial and temporal variables; and the resulting wave is characterized by the presence of peakons, the appearance of which fade in density as the order of fractional derivative approaches 2. It is obtained that the transversely isotropic structure of the material of the cylinder increases the wave speed and introduces an additional term in the wave equation. Further, it is observed that the law relating the non-zero components of the Cauchy stress tensor in the cylinder under consideration generalizes the hypothesis of plane strain in classical elasticity theory. This study reinforces the view that fractional derivative is suitable for modeling anomalous wave propagation in media.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 추계학술대회 논문집
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• pp.138-143
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• 2001

Based on mild slope equation and parabolic approximation the forward diffraction of monochromatic waves by a straight breakwater are studied numerically. The characteristics and effects of stem wave along breakwater and the relations between the stem wave and incident wave angle are discussed.

• 한국해양공학회지
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• 제34권6호
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• pp.419-427
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• 2020

In this study, a particle image velocimetry (PIV)-based pressure estimation method was investigated, with application to the wave-in-deck loading phenomenon. An experimental study was performed in a two-dimensional wave tank using a fixed deck structure under a focused wave, obtaining local pressures by pressure sensors, global loads by load cells, and instantaneous velocity fields using the PIV measurement technique. The PIV-based pressure estimation method was applied using the Euler equation as the governing equation, and the proper time step for the wave impact pressure was studied using the normalized root-mean-square deviation. The pressure estimation method showed good agreement for the local impact pressure in comparison with the measured pressure by the pressure sensors. However, some differences were observed in the peak pressure due to the limitations of the Euler equation and the sampling rate of the measurement system. Using the estimation method, the pressure fields during wave-in-deck loading were determined in the study, with an analysis of the mechanism of impact and negative pressure occurrence.

• 한국항만학회지
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• 제13권1호
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• pp.155-166
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• 1999

The construction of the coastal structures and reclamation work causes the circulation reduced in the semi-closed inner water area and the unbalanced sediment budget of beach results in an alteration of beach topography. Among the various fluid motions in the nearshore zone water particle motion due to wave and wave-induced currents are the most responsible for sediment movement. Therefore it is needed to predict the effect of the environmental change because of development and so the prediction of wave transformation dose. The purpose of this study is to introduce the relation between waves wave-induced currents and sediment movement. In this study we will show numerical method using energy conservation equation involving reflection diffraction and reflection and the surfzone energy dissipation term due to wave breaking is included in the basic equation. For the wave-induced current the momentum equation was combined with radiation stresses lateral mixing and friction Various information is required in the prediction of wave-induced current depending on the prediction tool. We can predict changes in wave-induced current from the distribution of wave especially near the wave breaking zone. To evaluate these quantities we have to know the local condition of waves mean sea level and so on. The results from the wave field and wave-induced current field deformation models are used as input data of the sediment transport and bottom change model. Numerical model were established by a finite difference method then were applied to the development plan of the eastern Pusan coastal zone Yeonhwa-ri and Daebyun fishing port. We represented the result with 2-D graphics and made comparison between before and after development.

• Coupled systems mechanics
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• 제1권2호
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• pp.183-204
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• 2012

A method for the analysis of wave scattering in 3-D elastic full space is developed by means of the coupled boundary-volume integral equation, which takes into account the effects of both the boundary of inclusions and the uctuation of the wave field. The wavenumber domain formulation is used to construct the Krylov subspace by means of FFT. In order to achieve the wavenumber domain formulation, the boundary-volume integral equation is transformed into the volume integral equation. The formulation is also focused on this transform and its numerical implementation. Several numerical results clarify the accuracy and effectiveness of the present method for scattering analysis.

• 한국해안해양공학회지
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• 제16권2호
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• pp.103-107
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• 2004

파활동경사라는 새로운 무차원 수를 도입하여 소파제의 중량 산정식을 개발하였다. van der Meer(1987)는 Iribarren 수를 도입하여 중량 산정식을 개발하였는데 조건에 따라 전혀 다른 분포경향을 보였다. 반면에 파활동경사를 도입한 산정식은 조건에 관계없이 동일한 분포경향을 보였으며, 비례상수를 Iribarren 수의 함수로 취하였을 때 매우 높은 정밀도를 갖는 경험식을 도출하였다.

• 한국해안해양공학회지
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• 제11권1호
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• pp.68-74
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• 1999

본 연구에서는, 等水深의 港內波高分布 計算을 목적으로 이미 확립되어져 있는 Green 函數法을 變水深場에 適用하기 위하여 變數深場의 点源波에 대한 基本解를 구한다. 平面波浪場의 가장 일반적인 緩傾斜方程式을 基礎方程式으로 하여, 点源波가 圓環狀으로 전파하는 狀況을 나타내기 위하여 이것을 極座標로 표시하고, 進行性의 波를 간편하게 計算할 目的으로 抛物形 方程式으로 근사화하였다. 유도된 抛物形 波動方程式으 差分化하여 變水深場에서의 点源波의 基本解를 數値的으로 구하였으며 嚴密解와 비교하여 수치해의 타당성을 검토하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.733-742
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• 2020

Taking the cylindrical float of the floating fence of a floating litter collection device as the research object, based on the shallow immersion characteristics of the cylindrical float, the Morison equation is modified, and the interaction between regular waves and the partially immersed horizontal cylindrical float is discussed in combination with scale model test. The results show that the modified Morison equation can accurately predict the wave force of the horizontal cylindrical float and reveal the influence of amplitude, immersion depth and period on the wave force of the cylindrical float. For partially immersed cylindrical floats, the wave force increases with the increase in wave height and decays with the increase in period. The positive value distribution of the wave force is larger than that of the negative direction, and the difference between the positive and negative directions is mainly affected by the immersion depth.

• 한국항공우주학회지
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• 제33권7호
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• pp.18-25
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• 2005

본 연구에서는 뒷전, 전단류와 초기교란의 상호작용에 의한 불안정파의 생성 기제의 분석과 뒷전 산란현상을 고차의 전산공력음향학을 이용하여 모사하였다. 수치적 알고리즘은 Hybrid 기법에 기초하였으며, Simple Linearized Euler Equation과 Full Linearized Euler Equation의 결과를 비교를 통해 정상류 구배항이 불안정파의 생성에 중요한 역할을 함을 볼 수 있었다. 또한 Full Navier-Stokes Equation을 이용한 결과와 비교함으로써, Full Linearized Euler Equation은 뒷전의 초기 근접장에서 불안정파를 해석하는데 있어서 Full Navier-Stokes Equation 보다 효율적임을 알 수 있다.