• 한국수자원학회논문집
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• 제36권3호
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• pp.413-422
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• 2003

본 연구에서는 Boussinesq 방정식을 이용하여 유도된 장파를 지배하는 한창의 상미분방정식을 이용하여, 완만히 변하는 일정경사면의 정현파형 지형에서의 Bragg 반사를 해석하였다. 입사파는 위상이 다른 두 단파의 중첩에 의해 생성된 파군을 사용하였다. Bragg 반사 조건에서 해저지형의 경사가 장파의 반사에 미치는 영향에 대하여 검토하였으며, 해저지형의 경사가 클수록 반사는 크게 나타났다. 이는 수심의 감소로 인해 비선형성이 증가하였으며, 이로 인한 파랑의 천수효과로 입사파의 파고가 상승하여, 반사 역시 크게 나타난 것으로 판단된다.

• 한국해양공학회지
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• 제25권2호
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• pp.29-35
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• 2011

In order to effectively control waves in a coastal zone, Multi-Cylinder Piles have been suggested as economic structures. A numerical analysis was conducted using the Delft-3D: WAVE module based on SWAN, which considered wave shoaling and refraction. Moreover, irregular waves were used to investigate the hydrodynamic characteristics of the wave interaction with the structure. In this paper, a numerical analysis was carried out to research the effect of wave control through a wave height analysis concerning an existing, concrete wave breaker and multi-cylinder piles placed at the same location. As a result, the effect of the wave control is shown using the wave breaker, multi-cylinder piles, and existing data.

• 한국해안해양공학회지
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• 제13권4호
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• pp.296-308
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• 2001

Wei et al.의 완전비선형 Boussinesq방정식을 4차의 Adams predictorcorrector기법을 사용하여 차분하고 면 내부조파기법과 스폰지 경계충을 사용하였으며 쇄파구조를 추가하였다. 면 내부조파기법을 사용해 목적파를 잘 재현할 수 있었다. 비선형성이 부각되는 고립파의 천수실험을 통해 완전비선형 모형의 정화성을 확인할 수 있었고 해저평붕으로 인한 규칙파의 변형을 모의해 보았다. 쇄파 수치실험을 통해 적용된 쇄파구조의 특성을 확인해 보았고 수중천퇴에 대한 이차원 파랑전파 수치실험을 통해 비선형 모형의 중요성을 확인하였다.

• Ocean Science Journal
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• 제43권2호
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• pp.81-90
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• 2008

A study of estuarine flows during a neap tide was performed using 13-hour roving acoustic Doppler current profiles (ADCP) and conductivity-temperature-depth (CTD) profiles in the Altamaha River estuary, Georgia, U.S.A. The least-squared harmonic analysis method was used to fit the tidal ($M_2$) component and separate the flow into two components: the tidal and residual ($M_2$-removed) flows. We applied this method to depth-averaged data. Results show that the $M_2$ component demonstrates over 95% of the variability of observation data. As the flow was dominated by the $M_2$ tidal component in a narrow channel, the tidal ellipse distribution was essentially a back-and-forth motion. The amplitude of $M_2$ velocity component increased slightly from the river mouth (0.45 m/sec) to land (0.6 m/sec) and the phase showed fairly constant values in the center of the channel and rapidly decreasing values near the northern and southern shoaling areas. The residual flow and transport calculated from depth-averaged flow shows temporal variability over the tidal time scale. Strong landward flows appeared during slack waters which may be attributed to increased baroclinic forcing when turbulent mixing decreases.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2014년도 춘계학술대회
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• pp.255-257
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• 2014

항내 정온도는 항만의 박지(泊地) 내 수면의 정온한 정도를 나타내는 것으로서, 선박의 접이안, 하역작업과 관계가 있지만 이보다 안전한 피항지로서의 최소한의 수역을 파악하기 위한 중요한 지표이다. 따라서, 항내 정온도 예측시 항외로부터 입사하는 파랑의 굴절, 회절, 천수 및 반사 등에 의한 항내파고 및 파향의 변화를 복합적으로 해석해야 한다. 그러나 항내 정온도 검토를 위하여 현재 운용 중인 수치모형실험은 각각의 특성에 따른 결과의 상이함에 따라 이에 대한 기본적인 재검토가 필요한 것으로 판단되며, 이에 본 연구에서는 후포항을 대상으로 수치모형실험결과와 비교함으로써 현재 운용 중인 모형의 타당성을 검토하였다.

• Journal of the korean society of oceanography
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• 제38권3호
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• pp.143-155
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• 2003

Current and sea level were observed in spring 1999 by a bottom mounted ADCP and tide gauge in the central part of the South Sea of Korea. With respect to the front, the distribution of isotherms is prograde in the offshore region whereas that of isohalines is retrograde, especially in the coastal area. The combined effect results in shoaling of isopycnals at the front. This distribution corresponds to a westward coastal flow on the northern side of the front and the eastward Tsushima Warm Current (TWC) to the south, determined by vessel-mounted ADCP observations. The low-frequency current shows either alternating clockwise-counterclockwise rotation or else persistent eastward motion depending on the frontal motion. Fluctuations of wind, sea level and current are coherent at period of 3-4 days and show some characteristics of Ekman-like dynamics.

• 한국해안해양공학회지
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• 제5권4호
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• pp.263-270
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• 1993

일정 경사 해저면을 갖는 해안에 입사한 파가 천수변형을 거치고 쇄파하는 과정에서 발생하는 라디에이션 응력 및 평균수위 변화를 다루었다. 일반적으로 선형파동 이론에 의해 산정된 라디에이션 응력은 쇄파대내 및 그 부근에서 과대 평가되는데, 이것이 평균수위 변동의 계산치와 실험치와의 불일치의 원인이 된다. 본 연구에서는 Svendsen(1984)이 제안한 라디에이션 응력을 수정해서, 수심의 함수로 표시하고, 계산결과를 선형이론, 쇄파의 성분파고 스펙트럼에 기초한 Sawaragi(19梨) 방법 및 기왕의 실험데이타와 비교하였다. 수정된 Svendsen의 방법은 실험치와 비교적 양호한 일치를 보여 주었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권4호
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• pp.614-624
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• 2013

The resonance power buoy is a convincing tool that can increase the extraction efficiency of wave energy. The buoy needs a corresponding draft, to move in resonance with waves within the peak frequency band where wave energy is concentrated. However, it must still be clarified if the buoy acts as an effective displacement amplifier, when there is insufficient water depth. In this study, the vertical displacement of a circular cylinder-type buoy was calculated, with the spectrum data observed in a real shallow sea as the external wave force, and with the corresponding draft, according to the mode frequency of normal waves. Such numerical investigation result, without considering Power Take-Off (PTO) damping, confirmed that the area of the heave responses spectrum can be amplified by up to about tenfold, compared with the wave energy spectrum, if the draft corresponds to the peak frequency, even with insufficient water depth. Moreover, the amplification factor of the buoy varied, according to the seasonal changes in the wave spectra.

• 한국해양공학회지
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• 제10권4호
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• pp.149-159
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• 1996

Multipurpose development of the coast and ocean can be considered as multifunction construction combining the functions of coastal protection, waterfront amenity and creation or rehabilitation of habitats. Multfunction development of coastal and ocean spaces can be accomplished by applying the ecosystem control structure of artificial habitats which will cultivate fishing ground with ecological harmony to the coastal protection system. To evaluate the applicability of ecosystem control structures as as fundamental coastal protection structure, wave control function of the structure is studied by numerical and physical analyses. Dimensional analysis and hydraulic experiment point out the importance of width and crest depth of ecosystem control structure, construction water depth and wave steepness. Wave control efficiency is estimated by the attenuation coefficient $(K_H)$ according to wave steepness $(H_0/L_0)$, relative constructed water depth $(h_i/H_0)$, relative berm width $(B/L_0)$ and relative crest depth $(h_B/H_0)$ of eosystem control structure. Empirical fomulas are suggested based on the results of model test by applying the multiple model based on this experimental results and numerical wave shoaling-dissipation-breaking model appears to be valid for the analysis of wave transformation around ecosystem control structure in the coastal waters.

• 한국항해항만학회지
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• 제30권2호
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• pp.125-130
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• 2006

Waves, which are the main source of ship motions in a seaway, considerably affect the performance of a ship. The study of waves and their impact on ship motions within harbors is an important aspect of the design and operation of harbors. The prediction of incoming groups of waves is particularly important for evaluating ship motion within a harbor. Such a prediction makes it possible to evaluate ship safety more accurately. The wave transformation model reported here is applied to actual ports based on Boussinesq wave equations both non-linear and dispersive wave processes be considered in order to capture physical effects such as wave shoaling, refractions, reflection and diffraction in variable depth environments. The prediction of incoming groups of waves is particularly important for evaluating ship motion within a harbor, Such a prediction makes it possible to evaluate ship safety more accurately and provide safe wave informations for navigation. Furthermore, a wave information support system is proposed for entering ships as one technique for improving the safety of ship operations. This system predicts the run of waves and reduces the danger by identifying the most dangerous point near the harbor entrance at the small wave groups.