• International Journal of Naval Architecture and Ocean Engineering
• /
• 제7권3호
• /
• pp.610-625
• /
• 2015

In this paper the wave run-up around a circular column in regular waves is numerically calculated to investigate the applicability of the Modified Marker-Density (MMD) method to prediction of wave run-up around an offshore platform. The MMD method is one of the methods to define the highly nonlinear free surface. The governing equations are the Navier-Stokes equations and the continuity equation which are computed in Cartesian grid system. To validate incident waves generated by numerical simulation, those are compared with the solutions of the Stokes $5^{th}$ order wave theory. The wave run-up simulations are performed varying the steepness and period of incident waves as referred experimental data. The numerical results are compared to the experimental data and the results show good agreements.

• 한국해안·해양공학회논문집
• /
• 제26권6호
• /
• pp.397-404
• /
• 2014

우리나라의 항만정온도 검토 방법에는 이상 시 항내정온도 검토와 항만가동율 검토 등이 있으며 대부분의 경우에 두 가지 방법을 모두 수행하고 있다. 전자에서는 정온도 기준을 합리적인 근거가 없는 항내파고 절대치로 판단하고 있는 문제점이 있으며 그 실효성에도 의문이 제기된다. 후자에서는 초과출현율 파 또는 장기간의 실측 및 역추산 자료의 파향-주기군을 사용하여 항만가동율을 산정하는 방법 등이 사용되고 있는데 이들 중 초과출현율 파의 사용은 정확도에 문제가 있으므로 장기간 자료를 사용하는 것이 바람직하다. 또한, 현재 적용되는 하역한계파고의 기준은 너무 단순하여 실제 상황을 반영하는데 한계가 있다. 본 논문에서는 부산항 신항에서 관측한 파고 실측자료를 사용하여 현행 항만정온도 및 항만가동율 검토방법의 문제점을 실질적으로 입증하였으며 실측자료의 중요성을 강조하였다. 향후 우리나라 주요 항만 내 외에서 장기간의 실측 자료를 확보함으로써 개선된 항만정온도 기준을 마련하는데 적극적으로 활용하는 것이 바람직하다.

• 한국해안·해양공학회논문집
• /
• 제31권6호
• /
• pp.395-402
• /
• 2019

기존 케이슨의 안정성을 높이기 위해 신규 케이슨을 기존 케이슨 전면 또는 후면에 추가로 설치하여 보강하는 설계 및 시공사례가 발생되고 있다. 본 연구에서는 고유함수전개법을 이용하여 원형케이슨으로 구성된 기존 방파제 후면에 신규 원형케이슨이 설치될 경우 각 원형케이슨에 작용하는 파력특성을 분석하였다. 수치해석의 신뢰성을 확보하기 위해 상용화 프로그램인 ANSYS AQWA의 수치 해석결과와 비교를 수행하였으며, 원형 케이슨 추가설치에 따른 파와 구조물의 상호작용 영향을 고려하여 각 원형케이슨에 작용하는 파력을 산출하였다.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2005년도 학술발표회 논문집
• /
• pp.34-41
• /
• 2005

This paper presents a new infinite element for modeling far-field of wave propagation problem in a fluid-saturated two-phase medium. The infinite element can simulate arbitrary number of multiple wave components, while wave components in infinite element developed by other researchers was limited to two compressional waves. The accuracy and effectiveness of the proposed method have demonstrated using 1-D and 2-D wave propagation problems.

• 대한조선학회논문집
• /
• 제39권1호
• /
• pp.38-48
• /
• 2002

파랑집중 이론에 기초하여 모형시험수조에서 다방향 극한파를 생성하는 연구를 수행하였다. 파랑의 집중도에 대한 파향 범위, 주파수 폭, 중심 주파수 등의 영향을 고찰하였다. 등파고와 등기 울기 스펙트럼 모델에 의한 결과를 서로 비교하였으며, Boussinesq 방정식과 유한요소법에 기초한 수치해와 이론해를 또한 서로 비교하였다. 효율적인 파랑집중을 위해서는 파향과 주파수 모두를 효과적으로 제어하는 것이 필수적이다. 파랑집중도는 중심주파수 보다는 주파수 폭에 좌우되며, 동일한 조건하에서 두 스펙트럼 모델은 동등한 정도의 파랑집중 효율을 나타낸다.

• 한국항해항만학회지
• /
• 제36권9호
• /
• pp.729-735
• /
• 2012

The primary wave energy conversion by a three-dimensional bottom-mounted oscillating water column (OWC) wave power device in regular waves has been studied. The linear potential boundary value problem has been solved following the boundary matching method. The optimum shape parameters such as the chamber length and the depth of the front skirt of the OWC chamber obtained through two-dimensional numerical tests in the frequency domain have been applied in the design of the present OWC chamber. Time-mean wave power converted by the OWC device and the time-mean second-order wave forces on the OWC chamber structure have been presented for different wave incidence angles in the frequency-domain. It has been shown that the peak period of $P_m$ for the optimum damping parameter coincides with the peak period of the time.mean wave drift force when ${\gamma}=0$.

• 대한조선학회 특별논문집
• /
• 대한조선학회 2005년도 특별논문집
• /
• pp.15-21
• /
• 2005

In this paper, the procedure of generation and application of nonlinear wave loads for structural design of large container carrier was described. Ship motion and wave load was calculated by modified strip method. Pressure acting on wetted hull surface was calculated taking into account of relative hull motion to the wave. Design wave height was determined based on the most sensitive wave length considering rule vertical wave bending moment at head sea or fellowing sea condition. And the enforced heeling angie concept which was introduced by Germanischer Lloyd (GL) classification had been used to simulate high torsional moment in way of fore hold parts similar to actual sea going condition. Using wave load generated from this dynamic load calculation, FE analyses were performed. With this result, yielding, buckling, hatch diagonal deflection and fatigue strength of hatch corners were reviewed based on the requirement of GL classification. The results of FE analysis show good compatibility with GL classification.

• 한국재료학회지
• /
• 제32권7호
• /
• pp.320-325
• /
• 2022

Single OLED and tandem OLED was manufactured to analyze the electroluminescence characteristics of DC driving, AC driving, and full-wave rectification driving. The threshold voltage of OLED was the highest in DC driving, and the lowest in full-wave rectification driving due to an improvement of current injection characteristics. The luminance at a driving voltage lower than 10.5 V (8,534 cd/m²) of single OLED and 20 V (7,377 cd/m²) of a tandem OLED showed that the full-wave rectification drive is higher than that of DC drive. The luminous efficiency of OLED is higher in full-wave rectification driving than in DC driving at low voltage, but decrease at high voltage. The full-wave rectification power source may obtain higher current density, higher luminance, and higher current efficiency than the AC power source. In addition, it was confirmed that the characteristics of AC driving and full-wave rectification driving can be predicted from DC driving characteristics by comparing the measured values and calculated values of AC driving and full-wave rectification driving emission characteristics. From the above results, it can be seen that OLED lighting with improved electroluminescence characteristics compared to DC driving is possible using full-wave rectification driving and tandem OLED.

• 소음진동
• /
• 제10권4호
• /
• pp.610-614
• /
• 2000

Cellular Automata(CA)s are used as a simple mathematical model to investigate self-organization in statistical mechanics, which are originally introduced by von Neumann and S. Ulam at the end of the 1940s. CAs provide a framework for a large class of discrete models with homogeneous interactions, which are characterized by the following fundamental properties: 1) CAs are dynamical systems in which space and time are discrete. 2) The systems consist of a regular grid of cells. 3) Each cell is characterized by a state taken from a finite set of states and updated synchronously in discrete time steps according to a local, identical interaction rule. 4) The state of a cell is determined by the previous states of a surrounding neighborhood of cells. A cellular automaton has been attracted wide interest in modeling physical phenomena, which are described generally, partial differential equations such as diffusion and wave propagation. This paper describes one and two-dimensional analysis of wave propagation phenomena modeled by CA, where the local interaction rules were derived referring to the Lattice Gas Model reported by Chen et al., and also including finite difference scheme. Modeling processes by using CA are discussed and the simulation results of wave propagation with one wave source are compared with that by finite difference method.

• 한국전자파학회논문지
• /
• 제9권3호
• /
• pp.296-304
• /
• 1998

TV파와 같은 수명편파용 광대역 전파흡수체를 설계하기 위해 평판 페라이트층 위에 핀형 페라이트를 적충한 전파흡수체를 제안하였다. 제안한 전파홉수체를 등가재료정수법을 이용하여 최적 치수를 구하고, 이 때의 전파흡수능을 기존의 흡수체의 흡수능과 비교하였다, 둥가재료정수법이라는 근사법의 타당성을 확인하기 위하여 Hashin-Strikman의 경계치를 이용한 경우의 실효유전율과 비교하였다. 나아가서, 등가재료정수법에 의한 전파흡수능과 도파관모델로 근사하여 FDTD법으로 구한 전파홉수능을 비교한 결과, 이들은 서로 잘 일치함을 확인하였다. 따라서, 제안한 단일편파용 전파흡수체는 30 MHz-5830 MHz의 광대역 특성을 가지며, 이러한 구조의 전파흡수체를 설계 또는 해석하는 데에는 등가재료정수법으로도 충분히 유효함이 입증되었다.