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이관홍,이희준 한국해양과학기술원 2008 Ocean and Polar Research Vol.30 No.4
The sediment resuspension and diffusion model is an integral part of a sediment transport and morphologic change model. We examined a vertical one-dimensional sediment resuspension and diffusion model using field data collected at about 10-m depth off the Saemangeun 4th dike. The field data include waves, currents and suspended sediment concentration near the bed for about a day in May, 2007. The suspended sediment concentration obtained from the 1D model overestimated the observation about two orders of magnitude with single grain size and multiple grain sizes. The incorporation of the bed armoring effect, which adjusts the amount of suspended sediment with the available bed sediment, improved the agreement between the model and observation within a factor of two. The sediment resuspension and diffusion model is an integral part of a sediment transport and morphologic change model. We examined a vertical one-dimensional sediment resuspension and diffusion model using field data collected at about 10-m depth off the Saemangeun 4th dike. The field data include waves, currents and suspended sediment concentration near the bed for about a day in May, 2007. The suspended sediment concentration obtained from the 1D model overestimated the observation about two orders of magnitude with single grain size and multiple grain sizes. The incorporation of the bed armoring effect, which adjusts the amount of suspended sediment with the available bed sediment, improved the agreement between the model and observation within a factor of two.
이내비게이션을 활용한 해양환경관측 및 빅데이터 분석방안
이관홍,박재훈,하호경,김도완,이우주,김홍태,신현정,LEE, GUAN-HONG,PARK, JAE-HUN,HA, HO KYUNG,KIM, DO WAN,LEE, WOOJOO,KIM, HONGTAE,SHIN, HYUN-JUNG 한국해양학회 2018 바다 Vol.23 No.4
본 연구에서는 이내비게이션 시스템이 장착된 연안 및 국제여객선을 활용하여 효율적으로 해양환경관측을 실시하고 관측된 해양 환경 빅데이터를 분석할 수 있는 방안을 제시하였다. 먼저, 이내비게이션 시스템과 운영 개념을 소개하고, 우리나라 연안의 해양환경모니터링 현황을 개괄한 후, 기존 관측망의 단점을 보완하고 장점을 강화할 수 있도록 이내비게이션을 활용한 해양환경모니터링 관측방법과 관측요소(기상, 물성, 유속 및 수심)를 제안하였다. 또한, 이내비게이션 시스템이 장착된 여객선에서 관측한 자료를 실시간으로 분석하는 시공간 혼합효과모형, 앙상블기법 및 무요소기법과 같은 해양빅데이터 분석 기법을 제안하였다. 본 연구는 연안 선박과 소형어선에 중점을 둔 한국형 이내비게이션 추진에 도움이 될 것으로 기대한다. This study proposes a cost-effective method to monitor coastal environments using e-Navigation-implemented domestic and international ferries, and to analyze big data of records such as wind, temperature, salinity, waves, and currents that are gathered through e-Navigation system. First, we present the concept and architecture of e-Navigation operation system based on the General Information Center on Maritime Safety and Security. Then, the marine observation system that can be applied to ferries operating in our nation's territory is discussed. Analytical methods, such as spatio-temporal mixed effects model, ensemble method, and meshfree method, in handling real-time big data obtained by the e-Navigation observing system are then explained in detail. This study will support the implementation of the Korean e-Navigation project that focuses on the safety of small vessels such as coasters and fishing vessels.
Sediment eddy diffusivity and selective suspension under waves and currents on the inner shelf
이관홍 한국지질과학협의회 2008 Geosciences Journal Vol.12 No.4
Sediment diffusivity and effective settling velocity, we, (or equivalently grain size) of near-bed suspended sand was inferred from observed concentration profiles. Concentration data were obtained at 20-m depth off Dounreay, Scotland, and at 13-m depth off Duck, North Carolina, USA. These data accommodate different dynamic conditions (from wave-dominated at Dounreay to wind-driven current-dominated at Duck) and different sediment properties (median size of bed sediment ranging from 120 to 290 m). Regression of observed concentration profiles using the Rouse-type diffusion equation yielded the Rouse parameter P=we/u*, where is von Karman’s constant, u* is the characteristic shear velocity, and we is the effective settling velocity. Linearly increasing eddy diffusivity extended several times higher than the classical wave boundary layer and was not observed to strongly change slope at the top of the wave boundary layer. Instead, u* within several 10s of cm of the bed was nearly equal to wave-current shear velocity (u*cw) or current shear velocity (u*c) depending on whether conditions were wave- or current-dominated. For the Rouse parameter, it was found that u* u*c for u*c > ws and u* u*cw for u*c < ws, where ws is the median settling velocity of the bed sediment. The effective settling velocity in suspension (we) was, in turn, evaluated from P using independent estimates of u*cw and u*c. The inferred size of suspended sediment varied in response to forcing conditions. For an inverse Rouse number u*sf/ws near one, where u*sf is the skin-friction shear velocity, the representative grain size of suspended sediment approached the median size of bed sediment. A similar trend was seen for u*cw/ws or u*c/ws near two, depending on whether conditions were wave or current dominated. With increasing (or decreasing) u*/ws, the grain size of suspended sediment also increased (or decreased), suggesting selective suspension of sediment particles as a function of flow strength.
이관홍,강기룡 한국해양과학기술원 2018 Ocean science journal Vol.53 No.3
A field campaign was conducted to better understand the influence of wave action, in terms of turbulence and bed shear stress, on sediment resuspension and transport processes on a protected tidal flat. An H-frame was deployed in a tidal channel south of Gangwha Island for 6 tidal cycles during November 2006 with instrumentation including an Acoustic Doppler Velocimeter, an Acoustic Backscatter System, and an Optical Backscatter Sensor. During calm conditions, the current-induced shear was dominant and responsible for suspending sediments during the accelerating phases of flood and ebb. During the high-tide slack, both bed shear stress and suspended sediment concentration were reduced. The sediment flux was directed landward due to the scour-lag effect over a tidal cycle. On the other hand, when waves were stronger, the wave-induced turbulence appeared to keep sediments in suspension even during the high-tide slack, while the current-induced shear remained dominant during the accelerating phases of flood and ebb. The sediment flux under strong waves was directed offshore due to the sustained high suspended sediment concentration during the high-tide slack. Although strong waves can induce offshore sediment flux, infrequent events with strong waves are unlikely to alter the long-term accretion of the protected southern Gangwha tidal flats.