• 한국해양공학회지
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• 제34권2호
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• pp.128-135
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• 2020

When high waves and storm surge strike simultaneously, the characteristics of the fluid field change drastically from overtopping according to the wave runup height to overflow through a transition state that combines overtopping and overflows. However, an estimation model or evaluation method has not yet been established because there is not enough engineering data. This study developed a wave overtopping-overflow transition model based on a full-scale experiment involving wave overtopping and overflow transition, which appropriately reproduced the effect of waves or the temporal change in inundation flow. Using this model to perform a calculation for the wave overtopping and overflow transition process under typical circumstances, this study determined the wave runup height and features of the inundation flow under time series changes as an example.

• 한국항만학회지
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• 제10권1호
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• pp.53-61
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• 1996

This paper describes the effect of wave control using submerged flat plate by the numerical calculation and the hydraulic model test. The boundary element method is used to develop a numerical solution for the flow field caused by monochromatic oblique waves incident upon an infinitely long, sumerged flat plate situated in arbitrary water depth. The effect of wave blocking is examined according to the change of length, submerged depth of flat plate and incident angles. Numerical results show that longer length, shallower submergence of flat plate and larger incident angles enhance the effect of wave blocking. To validate numerical analysis method, hydraulic model test was conducted in 2-D wave flume with 60 cm metal sheet. Reflected waves are extracted from water surface elevation in front of the location of a submerged plate by least square method with 3 wave gages. From comparing experimental results with numerical results, efficiency of numerical analysis method by this study could be confirmed well within wide ranges of wave frequencies.

• 비파괴검사학회지
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• 제23권6호
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• pp.635-644
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• 2003

To ensure the reliability of ultrasonic nondestructive testing techniques for modern structural materials, the effects of anisotropy and inhomogeneity and the influence of non-planar component geometries on ultrasonic wave propagation have to be taken into account. In this article, fundamentals and applications of two analytical approaches to three-dimensional elastic beam field calculation are presented. Results for both isotropic materials including curved interfaces and for anisotropic media like composites are presented, covering field profiles for various types of transducers and the modeling of time-dependent rf-signals.

• 한국항해학회지
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• 제22권1호
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• pp.55-62
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• 1998

본 논문에서는 TV 주파수에 있어서 건조물에 의해 발생하는 전자파장해를 평가하기 위해 건축물 주위의 산란전자계를 수치계산하였다. 건축물 외벽에 전파흡수체를 부분적으로 부착한 경우 콘크리트면의 노출면적과 반사전계강도와의 관계를 조사하였다. 계산된 산란 전자계로부터 DU 비를 구해 TV 고스트방지를 위하여 건축물 외벽에 부착할 전파흡수체에 요구되는 반사 감쇠량을 구하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.202-207
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• 2001

The added resistance of a ship advancing in waves can be split into the resistance due to the radiation wave and the resistance due to the diffraction wave. In this study, the former has been calculated by a method based on Maruo's formula. The latter must be calculated by other methods. Ship motion is calculated by the usual strip method. The amplitude of two dimensional far-field waves is calculated using the improved Green integral equation. The present numerical method can be used for the estimation of the added resistance due to the radiation wave since the present numerical result is much smaller than other existing numerical results considered to be overestimated.

• 한국해양공학회지
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• 제21권1호
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• pp.1-6
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• 2007

While a typhoon is traveling, characteristics of its wind fields are continuously changing, producing severe changes in local water level and wave conditions, especially, when a typhoon comes into shallow water. However, there have not been many studies related to local typhoon effects, especially, considering real time changes of wind direction related to the coastal topography. In the study, the characteristics of the wind field by typhoon and topographical characteristics in shallow water are considered, as well as conditions of wave climate estimation. These are performed by the SWAN (Simulating waves nearshore) model, in order to estimate the growth of wave energy due to the wind field. It can be strongly suggested that the wave energy of theof an inner bay should be estimated when the direction of the bay entrance and the wind direction of the typhoon are identical. The result of the numerical calculations is in better agreement with the observed data than the result of the conventional estimation techniques.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.557-560
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• 2002

In this study, simulation of weak shock waves are peformed by a two-dimensional thermal fluid or compressible fluid model of the lattice Boltzmann method. The shock wave represents an abrupt change in fluids properties, in which finite variations in pressure, internal energies, and density occur over the shock thickness. The characteristics of the proposed model with a simple distribution function is verified by calculation of the sound speeds, and the shock tube problem. The reflection of a weak shock wave by wedge propagating in a channel is performed. The results agree well with those by finite difference method or by experiment. In the simulation of unsteady shock wave diffraction around a sharp corner, we show a flow field of vortical structure near the comer.

• 한국군사과학기술학회지
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• 제23권1호
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• pp.43-51
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• 2020

In this study, numerical analysis was carried out on a complex pressure field of blast waves caused by the detonation of high explosives in various environments. The generated blast waves propagated in the air, upon the sudden release of high energy induced by the explosion. Reflected waves were created when the pressure waves encountered certain obstacles such as the ground or the walls of structures. The propagation of the blast waves and its interaction with the reflected waves were simulated. An adaptive mesh refinement was applied to improve the efficiency of distribution of computer resource, for the computational calculation of the blast wave propagation in a wide open space. In addition, the integration of the calculation domains for the explosive and air were considered when the maximum density of the explosive region was below critical value. The results were verified by comparison with the pressure time history from blast wave experiments performed under two topographical conditions.

• 대한전자공학회논문지TC
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• 제47권5호
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• pp.60-68
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• 2010

통신서비스에 장애를 유발하는 전력선에 의한 전자유도 현상에 대한 방호를 위하여는 유도전압을 평가하여야 하고 상응한 대책을 수행하여야 한다. 유도전압을 평가하는 방식은 ITU 규격과 일본 유도자료로부터 국내에 도입되어 법률 고시화되어 있는데 이것으로 수용되지 못하는 유도 커플링상의 제원 요소들이 있다. 본 논문에서는 계산 수행 적용이 곤란한 범위를 포괄할 수 있도록 좀더 일반화된 고전적 유도 및 전자파 원론 해석 근간의 전자계 형성에 의한 소스와 관측점의 유도전압 산출 방식에 대한 기술을 분석하여 제시하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1407-1412
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• 2004

Impedance calculations of electric railway traction systems is essential to define characteristics and to design it. The self impedance is defined voltage drop rate per unit length, the mutual impedance is represented as a voltage induced to transmission line from transmission line. The self and the mutual impedance are influenced by ground return currents. The earth is considered as a semi-infinitely extended non-ideal conductor. The current of transmission line produces earth current induced magnetically and it flow through a path having minimum impedance. Carson proposed the impedance calculation formula using wave equations and magnetic field equations. Though the formula have an improper equation, that is still used as a standard impedance calculation method. This paper introduced an impedance calculation method that the complex depth of earth return method assumes that the current in conductor returns through an imagined earth depth path located directly under original conductor at a depth of. In this paper, we showed that this proposed method has a closed form and is easier than Carson's.