• Water Engineering Research
• /
• 제1권3호
• /
• pp.187-197
• /
• 2000

This paper describes an adaptive quadtree-based 2DH wave-current interaction model which is able to predict wave breaking, shoaling, refraction, diffraction, wave-current interaction, set-up and set-down, mixing processes (turbulent diffusion), bottom frictional effects, and movement of the land-water interface at the shoreline. The wave period-and depth-averaged governing equations are discretised explictly by means of an Adams-Bashforth second-order finite difference technaique on adaptive hierarchical staggered quadtree grids. Grid adaptation is achieved through seeding points distributed according to flow criteria(e.g. local current gradients). Results are presented for nearshore circulation at a sinusoidal beach. Enrichment permits refined modelling of important localised flow features.

• Ocean Systems Engineering
• /
• 제6권1호
• /
• pp.23-60
• /
• 2016

The major objective of this study was to develop further understanding of 3D nearshore hydrodynamics under a variety of wave and tidal forcing conditions. The main tool used was a comprehensive 3D numerical model - combining the flow module of Delft3D with the WAVE solver of XBeach - of nearshore hydro- and morphodynamics that can simulate flow, sediment transport, and morphological evolution. Surf-swash zone hydrodynamics were modeled using the 3D Navier-Stokes equations, combined with various turbulence models (${\kappa}-{\varepsilon}$, ${\kappa}-L$, ATM and H-LES). Sediment transport and resulting foreshore profile changes were approximated using different sediment transport relations that consider both bed- and suspended-load transport of non-cohesive sediments. The numerical set-up was tested against field data, with good agreement found. Different numerical experiments under a range of bed characteristics and incident wave and tidal conditions were run to test the model's capability to reproduce 3D flow, wave propagation, sediment transport and morphodynamics in the nearshore at the field scale. The results were interpreted according to existing understanding of surf and swash zone processes. Our numerical experiments confirm that the angle between the crest line of the approaching wave and the shoreline defines the direction and strength of the longshore current, while the longshore current velocity varies across the nearshore zone. The model simulates the undertow, hydraulic cell and rip-current patterns generated by radiation stresses and longshore variability in wave heights. Numerical results show that a non-uniform seabed is crucial for generation of rip currents in the nearshore (when bed slope is uniform, rips are not generated). Increasing the wave height increases the peaks of eddy viscosity and TKE (turbulent kinetic energy), while increasing the tidal amplitude reduces these peaks. Wave and tide interaction has most striking effects on the foreshore profile with the formation of the intertidal bar. High values of eddy viscosity, TKE and wave set-up are spread offshore for coarser grain sizes. Beach profile steepness modifies the nearshore circulation pattern, significantly enhancing the vertical component of the flow. The local recirculation within the longshore current in the inshore region causes a transient offshore shift and strengthening of the longshore current. Overall, the analysis shows that, with reasonable hypotheses, it is possible to simulate the nearshore hydrodynamics subjected to oceanic forcing, consistent with existing understanding of this area. Part II of this work presents 3D nearshore morphodynamics induced by the tides and waves.

• 한국해양공학회지
• /
• 제27권4호
• /
• pp.33-44
• /
• 2013

IIn this study, a wave-surge-tide coupling numerical model was developed to consider nonlinear interaction. Then, this model was applied and calculations were made for a storm surge on the southeast coast. The southeast coast was damaged by typhoon "Maemi" in 2003. In this study, we used a nearshore wind wave model called SWAN (Simulating WAves Nearshore). In addition, the Meyer model was used for the typhoon model, along with an ocean circulation model called POM (Princeton Ocean Model). The wave-surge-tide coupling numerical model could calculate exact parameters when each model was changed to consider the nonlinear interaction.

• Ocean and Polar Research
• /
• 제25권3호
• /
• pp.287-302
• /
• 2003

The seasonal variations in the circulation of the water mass in the East Sea/Japan Sea have been simulated using a free surface primitive ocean model, RIAMOM (RIAM Ocean Model), comparing the results from GFDL-MOM1 (Geophysical Fluid Dynamics Laboratory Modular Ocean Model, version 1.1, hereafter MOM) with the GDEM (Generalized Digital Environmental Model) data. Both models appear to successfully reproduce the distinct features of circulation in the East Sea/Japan Sea, such as the NB (Nearshore Branch) flowing along the Japanese coast, the EKWC (East Korean Warm Current) flowing northward along the Korean coast, and the NKCC/LCC (North Korean Cold Current/Liman Cold Current) flowing southwestward along Korean/Russian coast. RIAMOM has shown better performance, compared to MOM, in terms of the realistic simulation of the flow field in the East Sea/Japan Sea; RIAMOM has produced more rectified flows on the coastal region, for example, the narrower and stronger NKCC/LCC than MOM has. There is however obvious differences between the model results and the GDEM data in terms of the calculation of the water mass; both models have shown a tendency to overpredict temperature and underpredict salinity below 50m; more diffusive forms of thermocline and halocline have been simulated than noted in GDEM data.

• 한국해안해양공학회지
• /
• 제5권4호
• /
• pp.369-383
• /
• 1993

잉여응력의 수정된 형태가 현 모델에서 제시되며 자유수면 이류항의 존재가 파랑에너지식과의 비교를 통해서 입증되었다. 수식모델은 편평한 해빈경사에서의 3차원적인 흐름의 순환패턴을 산출하며 그 결과는 실험치와 비교하여 좋은 일치를 보였다. 마지막으로 수심적분된 특성과 그 수직분포를 연계하여 전 연안역에 적용가능한 준3차원적 모델이 개발되었다.

• 한국해안해양공학회지
• /
• 제6권4호
• /
• pp.459-471
• /
• 1994

쇄파작용에 기인한 준 3차원적 연안류 순환 모델의 수치 기법을 제시한다. 지배 방정식은 근사 factorization 기법과 fractional step method를 사용하여 음해법으로 수치해석 되었고 분할된 식은 유한 체적법으로 차분된다. 계산된 3차원적 연안류 패턴의 한 예로서 Gourlay(1974)의 실험자료와 비교하여 간접적으로 모델의 타당성을 검증한다.

• Ocean and Polar Research
• /
• 제39권3호
• /
• pp.169-179
• /
• 2017

The "GeoDrifter" is a newly-developed surface drifter with high temporal resolution. It is the first time that high-frequency drifters have been deployed in the East/Japan Sea. The purpose of this study is to introduce the phenomena experienced by these drifters flowing along with the Tsushima Current across the East/Japan Sea, focusing on high-frequency variability, and to discuss them in comparison with previous observations. The observed basin-scale circulation of the Tsushima Current generally coincides well with the known schematic circulation. The GeoDrifter trajectories also show inertial oscillations almost everywhere in the oceanic regions of the East/Japan Sea, strong semi-diurnal tidal currents in the western part of Korea Strait, diurnal currents much stronger than semi-diurnal currents in the upstream region of the Nearshore Branch off the Japanese coast, and many warm eddies in the Yamato Basin, all comparable to the observational results reported in the previous studies. An interesting point is that the semi-diurnal tidal currents undergo a great spatial variation in the western part of the Korea Strait. The observed features that cannot be explained are, among others, strong counter-clockwise motions with oscillating period about 51 hours appearing in the upstream region of the Nearshore Branch off the Japanese coast and the different tidal behaviors between upstream and downstream regions of the latter.

• 한국해안·해양공학회논문집
• /
• 제23권4호
• /
• pp.276-284
• /
• 2011

파랑 잉여응력의 영향이 자동적으로 고려되므로 파랑으로부터 발생되는 흐름을 수치모의할 수 있는 수평점성 및 난류항이 포함된 Boussinesq 방정식 모형인 FUNWAVE를 이용하여, 다방향 불규칙파 조건으로 해운대 해안에서 발생하는 이안류를 수치모의하였다. 수치모의는 다방향 불규칙파의 전파양상과 지형에 의한 비선형 파랑변형을 잘 보여주고 있으며, 이러한 파랑변형과 해운대 지형특성이 반영되어 시간에 따라 발달하는 파랑유도 연안흐름 양상을 잘 보여준다. 수치모의 결과로 부터 이안류는 연안방향으로 상대적으로 수심이 깊은 곳에서 그리고 파고가 낮은 곳에서 이안류가 돌발적으로 발생 혹은 증폭될 수 있음을 확인하였다.

• 한국해양학회지
• /
• 제29권1호
• /
• pp.64-81
• /
• 1994

1992년까지의 국내 해양무기 연구동향을 간략히 정리하였으며, 이 분야의 연구논 문 및 조사활동을 분야별, 연구 해역별로 요약하여 해양물리 및 타 분야 연구활동의 참고가 될 수 있도록 정리하였다. 지금 까지의 해양물리 연구 대상해역은 전반적으로 한반도 주변 연근해역에 치우친 감이 있었고 연구내용도 전통적인 해수특성이나 조석 의 범위를 크게 벗어나고 있지 못하다. 따라서 앞으로의 연구는 basin-scale 순환에 역점을 두어 국내 해양학계의 큰 과제인 대마난류의 기원, 황·동중국해의 순환, 동해 의 3차원 순환을 해결하는 방향이 되어야 할 것이다.

• 한국해안해양공학회지
• /
• 제9권3호
• /
• pp.105-114
• /
• 1997

바람은 동해의 순환에 기여하는 중요한 외력이다. 1.5층 및 2.5층 감쇠중력 모형을 이용하여 동해의 순환을 시뮬레이션하여 대마난류의 분기, 동해안의 동한난류의 분기, 동한만 및 동해북부에서의 반시계 방향성 순환현상을 기존순환모형도와 비교하였다. 상층과 하층의 양상은 동해의 중앙부를 제외하고는 유사하였는데 극전선이 다음과 같이 서로 다른 두양상을 제시한다. 극전선의 북측의 주양상은 대부분의 계절에 발생하는 3개소의 반시계방향 와동이며 이 와동의 내측연안을 따라서 북한류와 리만한류가 흐른다. 극전선의 남측에서 상하 양층의 해류체계는 겨울과 봄의 상층순환을 제외하고는 시계방향 순환이다. 한국과 러시아 연안을 따라 류속구조는 순압적이나 동해중부는 경압적이다. 바람응력의 계절적 변화와 Ekman 수송(suction/pumping)을 시간변화를 갖는 공간적평균과 공간적변화를 갖는 시간적으로 수정된 바람응력을 부여함으로서 조사하였다. 동해의 서측과 북서측 해역의 반시계방향 와동의 형성에 있어서 바람응력 컬(curl)에 의한 국지적인 Ekman suction/pumping이 중요함을 확인하였다