• 전산구조공학
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• 제10권4호
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• pp.195-203
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• 1997

본 논문에서는 충격이나 폭발하중에 의해 발생되는 응력파와 균열의 상호작용을 수치적으로 계산하였다. 수치해법으로는 응력파의 물리적 특징을 잘 재현시켜주는 Bicharacteristic Method가 사용되었다. 충격하중에 대한 동적응력확대계수 K/sub I/(t)가 수치해석적으로 시뮬레이션된 코오스틱곡선에 의해 계산되었으며, Kalthoff의 실험에 의해 얻어진 결과와 잘 일치함을 보여주었다. 또한 균열 주변에 구멍이 존재하는 경우에 응력파가 구멍의 효과에 의해 균열의 응력확대계수에 미치는 영향을 조사하였으며 실험과 비교하여 만족할만한 결과를 얻었다.

• 한국해양공학회지
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• 제12권3호통권29호
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• pp.75-85
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• 1998

A finite difference model for predicting time-dependent, wave-induced nearshore current is studied. The model includes wave refraction, wave-current interaction, bottom friction and wind effect. This model iteratively solved the linear the linear set of conservation of both mass and momentum, which were time averaged (over one wave period) and depth integrated, for mean velocities and free surface displacement. Numerical simulations of nearshore current under oblique wave attack, and for wave and wind induced current on a longshore periodic beach are carried out. Longshore velocities tend to zero in some distances outside the breaker line. And the peak velocity is shifted shoreward at the breaker line. The results represent the general characteristics of the nearshore current induced by wave.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.675-678
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• 2008

The effect of wave and current interactions on jet-like current flowing against waves was investigated based on numerical simulations. The numerical simulations are conducted by a combined model system of REF/DIF(a wave model) plus SHORECIRC(a current model) and a Boussinesq equation model, FUNWAVE. In the simulations, regular and irregular waves refracted due to the jet-like opposing current were focused along the core region of current, and the jet-like current was earlier spreaded when the waves had larger wave heights. The numerical results show that the rapid change of wave height distribution in transverse direction near current inlet plays a significant role to spread the jet-like current. In other words, the gradients of radiation stress forcing in transverse direction have a more significant effect on the jet-like current than its relatively small gradients forcing in flowing direction, which tend to accelerate the current, do. In conclusion, it is indispensible to take into account the interaction effect of wave transformation and current characteristics when waves meet the opposing jet-like current such as river mouth.

• 한국해양공학회지
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• 제30권6호
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• pp.505-519
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• 2016

If the seabed is exposed to high waves for a long period, the pore water pressure may be excessive, making the seabed subject to liquefaction. As the water pressure change due to wave action is transmitted to the pore water pressure of the seabed, a phase difference will occur because of the fluid resistance from water permeability. Thus, the effective stress of the seabed will be decreased. If a composite breakwater or other structure with large wave reflection is installed over the seabed, a partial standing wave field is formed, and thus larger wave loading is directly transmitted to the seabed, which considerably influences its stability. To analyze the 3-D dynamic response characteristics of the seabed around a composite breakwater, this study performed a numerical simulation by applying LES-WASS-3D to directly analyze the wave-structure-soil interaction. First, the waveform around the composite breakwater and the pore water pressure in the seabed and rubble mound were compared and verified using the results of existing experiments. In addition, the characteristics of the wave field were analyzed around the composite breakwater, where there was an opening under different incident wave conditions. To analyze the effect of the changed wave field on the 3-D dynamic response of the seabed, the correlation between the wave height distribution and pore water pressure distribution of the seabed was investigated. Finally, the numerical results for the perpendicular phase difference of the pore water pressure were aggregated to understand the characteristics of the 3-D dynamic response of the seabed around the composite breakwater in relation to the water-structure-soil interaction.

• Interaction and multiscale mechanics
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• 제6권1호
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• pp.15-29
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• 2013

Phononic system composed of periodical elastic structures exhibit band gap phenomenon, and all elastic wave cannot propagate within the band gap. In this article, we consider one-dimensional binary materials which are periodically arranged as a 20-layered medium instead of infinite layered system for phononic system. The layered medium with finite dimension is subjected to a uniformly distributed sinusoidal loading at the upper surface, and the bottom surface is assumed to be traction free. The transient wave propagation in the 20-layered medium is analyzed by Laplace transform technique. The analytical solutions are presented in the transform domain and the numerical Laplace inversion (Durbin's formula) is performed to obtain the transient response in time domain. The numerical results show that when a sinusoidal loading with a specific frequency within band gap is applied, stress response will be significantly decayed if the receiver is away from the source. However, when a sinusoidal force with frequency is out of band gap, the attenuation of the stress response is not obvious as that in the band gap.

• Journal of Mechanical Science and Technology
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• 제15권3호
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• pp.366-373
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• 2001

A numerical analysis of shock wave/boundary layer interaction in transonic/supersonic axial flow compressor cascade has been performed by using a characteristics upwind Navier-Stokes method with various turbulence models. Two equation turbulence models were applied to transonic/supersonic flows over a NACA 0012 airfoil. The results are superion to those from an algebraic turbulence model. High order TVD schemes predicted shock wave/boundary layer interactions reasonably well. However, the prediction of SWBLI depends more on turbulence models than high order schemes. In a supersonic axial flow cascade at M=1.59 and exit/inlet static pressure ratio of 2.21, k-$\omega$ and Shear Stress Transport (SST) models were numerically stables. However, the k-$\omega$ model predicted thicker shock waves in the flow passage. Losses due to shock/shock and shock/boundary layer interactions in transonic/supersonic compressor flowfields can be higher losses than viscous losses due to flow separation and viscous dissipation.

• 한국보육지원학회지
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• 제11권1호
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• pp.461-480
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• 2015

본 연구는 영아기 자녀를 둔 어머니의 양육신념과 지지적 상호작용이 양육스트레스에 미치는 영향에 대하여 가구소득과 어머니의 취업여부에 따라서 차이가 나타나는지 살펴보는 것을 목적으로 하였다. 연구대상은 2010년 한국아동패널3차에 참가한 23-31개월 자녀를 둔 어머니들 중 가구소득과 취업여부로 분류한 4개 집단(낮은소득-비취업, 낮은소득-취업, 높은소득-비취업, 높은소득-취업)에 해당하는 770명이었다. 연구결과 어머니의 양육신념과 지지적 상호작용은 양육스트레스에 영향을 미치는 것으로 밝혀졌으며, 집단에 따라서 영향을 미치는 변인과 정도는 차이가 있었다. 4개의 모든 집단에서 공통적으로 어머니의 지지적 상호작용은 양육스트레스에 가장 큰 영향을 미치는 변인이었으며, 높은소득-비취업 집단에서는 유일한 변인이었다. 낮은소득-비취업 집단에서는 정서적, 도구적 가치와 성취기대, 인성에 대한 강조가, 낮은소득-취업 집단에서는 도구적 가치가, 높은소득-취업 집단에서는 정서적 가치와 성취기대가 양육스트레스에 영향을 미치는 것으로 나타났다. 이와 같은 연구결과는 취업여부와 가구소득과 관련된 어머니의 양육스트레스를 이해하기 위해서는 두 변인을 함께 고려할 필요가 있음을 시사해주고 있다.

• 한국가족관계학회지
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• 제21권1호
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• pp.51-76
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• 2016

Objectives: This study aims to investigate the effect of marital relationship on parenting stress among dual- and single-earner families. In particular, this study focuses on the interaction effect of marital relationship and father's child-rearing involvement on the parenting stress. To access factors associated with parenting stress, we included marital satisfaction and marital conflict as the dimensions of marital relationship in this study. Method: We employed data from the 5th wave of the Panel Study of Korean Children(PSKC) data. Our analysis sample consisted of 1,515 parents having at least one child aged under 4 years. Also, this study conducted descriptive statistics and multiple regression analysis. Results: First of all, marital satisfaction and marital conflict were significantly related to parenting stress for both mother and father in dual-earner families. While both indicators were significantly related to parenting stress for father, marital conflict only was a significant predictor for mother in single-earner families. Second, father involvement was a significant predictor for parenting stress for father in both dual- and single-earner families. Third, interaction effects were found between father involvement and marital conflict in the dual-earner families and between father involvement and marital satisfaction in the single-earner families. Conclusions: Based on the results, we recommended programs designed to enhance father's child-rearing involvement such as parenting education and community-based campaign. In addition, we recommended that policy and practice need to identify marital relationship dynamics to promote father's involvement and to reduce marital conflict in both dual- and single-earner families accordingly.

• Journal of Mechanical Science and Technology
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• 제18권1호
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• pp.153-166
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• 2004

This paper presents a comparative study of a fully coupled, upwind, compressible Navier-Stokes code with three two-equation models and the Baldwin-Lomax algebraic model in predicting transonic/supersonic flow. The k-$\varepsilon$ turbulence model of Abe performed well in predicting the pressure distributions and the velocity profiles near the flow separation over the axisymmetric bump, even though there were some discrepancies with the experimental data in the shear-stress distributions. Additionally, it is noted that this model has y$\^$*/ in damping functions instead of y$\^$＋/. The turbulence model of Abe and Wilcox showed better agreements in skin friction coefficient distribution with the experimental data than the other models did for a supersonic compression ramp problem. Wilcox's model seems to be more reliable than the other models in terms of numerical stability. The two-equation models revealed that the redevelopment of the boundary layer was somewhat slow downstream of the reattachment portion.

• Ocean Systems Engineering
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• 제1권4호
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• pp.337-353
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• 2011

In the present study, an offshore platform having large partial porous cylindrical members, which are composed of permeable and impermeable cylinders, is suggested. In order to calculate the wave force on large partial porous cylindrical members, the fluid domain is divided into three regions: a single exterior region, N inner regions and N beneath regions, and the scattering wave in each fluid region is expressed by an Eigen-function expansion method. Applying Darcy's law to the porous boundary condition, the effect of porosity is simplified. Wave excitation forces and wave run up on the structures are presented for various wave conditions. For the idealized three-dimensional platform having large partial porous cylindrical members, the dynamic response evaluations of the platform due to wave forces are carried out through the modal analysis. In order to examine the effects of soil-structure interaction, the substructure method is also applied. The displacement and bending stress at the selective nodal points of the structure are computed using various input parameters, such as the shear-wave velocity of soil, the wave height and the wave period. Applying the Monte Carlo Simulation (MCS) method, the reliability evaluations at critical structure members, which contained uncertainties caused by dynamic forces and structural properties, are examined by the reliability index with the results obtained from MCS.