• 한국수산과학회지
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• 제54권4호
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• pp.480-488
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• 2021

The term residence time is defined as the time taken for substances in a system to leave the system and is a useful concept to explain the physical environment characteristics of a coastal area. It is important to know the spatial characteristics of the residence time to understand the behavioral properties of pollutants generated in a marine system. In this study, the spatial distribution of average residence time was calculated for Gangjin Bay, Korea, using a hydrodynamic model including a particle tracking module. The results showed that the average residence time was about 10 days at the surface layer and about 20 days at the bottom layer. Spatially, this was the longest residence time in the southwestern sea. There was no significant difference in average residence time at the surface layer due to freshwater discharge, but spatial variation at the bottom layer was larger. The average residence time at the bottom layer decreased in the southwestern area due to freshwater discharge and increased in the northern area. This result suggests that the residence time of anthropogenic pollutants may have a large spatial difference depending on the freshwater discharge, and thus the time taken to influence cultured organisms may also vary.

• 한국환경과학회지
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• 제29권3호
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• pp.273-282
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• 2020

Residence time is defined as the time taken for a material in a system to leave the system. The residence time characteristics in shellfish aquaculture determine the dispersion of excretion from aquaculture farms, along with the supply of food by seawater exchange. In this study, we estimated the spatial distribution of average residence time in the shellfish farming area using a particle tracking model. As a result, a relatively short average residence time of about 20 days or less was calculated in most areas, but an average residence time of more than 40 days was calculated in the inner areas. Relatively long average residence times were calculated along the west coast compared to the east coast, with the longest average residence time of more than 50 days in the northwestern areas. It can be inferred that the disturbance of the benthic ecosystem caused by shellfish farms is likely to be large because of the relatively weak dispersion of excrement from shellfish farms located on the west coast, especially in the northwest region. This distribution of average residence time is important for understanding the potential effects of seawater exchange on the environmental sustainability of shellfish farms, along with the seawater circulation characteristics of Jaran Bay.

• 한국해양공학회지
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• 제23권2호
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• pp.47-52
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• 2009

A Lagrangian particle tracking model coupled with the Princeton Ocean Model were used to estimate the average residence time of coastal water in Masan Bay, Korea. Our interest in quantifying the transport time scales in Masan Bay was stimulated by the search for a mechanistic understanding of this spatial variability, which is consistent with the concept of spatially variable transport time scales. Tidal simulation was calibrated through a comparison with the results of semi-diurnal current and water elevation measured at the tidal stations of Masan, Gadeokdo. In the model simulations, particles were released in eight cases, including slack before ebb, peak ebb, slack before flood, and peak flood, during both spring and neap tides. The averaged values obtained from the particle release simulations were used for the average residence times of the coastal water in Masan Bay. The average residence times for the southeastern parts of Somodo and the Samho River, Masan Bay were estimated to be about 20~50days and 70~80days, respectively. The spatial difference for the average residence time was controlled by the tidal currents and distance from the mouth of the bay. Our results might provide useful for understanding the transport and behavior of coastal water in a bay and might be used to estimate the dissimilative capacity for environmental assessment.

• 한국가스학회지
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• 제19권3호
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• pp.25-31
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• 2015

본 연구에서는 부유 Mg분진의 최소발화온도(MIT)에 있어서 입자 체류시간이 어떠한 영향을 주는지를 실험자료와 입자속도의 계산결과를 사용하여 조사하였다. 평균입경이 증가하면 Mg분진의 MIT는 증가하는 반면에 입자 체류시간(Residence time)은 지수함수적으로 감소하여 분진의 발화 가능성이 저하되는 요인이 될 수 있음을 계산을 통해 확인할 수 있었다. 또한 온도증가에 의한 입자속도에의 영향은 평균입경이 클수록 미세하지만 증가하는 결과가 얻어졌다.

• 한국해안·해양공학회논문집
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• 제29권5호
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• pp.247-259
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• 2017

입자추적기법(Lagrangian Particle Tracking; LPT)을 적용한 수치모델을 이용하여 조력발전소 운영에 의한 시화호 외측해역에서의 체류시간 변화를 파악하였다. 수치모델의 실험안은 공간적인 분포 특징을 살펴보기 위하여 시화호 외측 해역을 4개 구역으로 나누어 구역별 평균체류시간을 산정하였다. 구역별 평균체류시간은 운영 전과 운영 중 모두 가장 외해에 위치한 지역(약 3일)에서 내만에 위치한 지역(약 13일)으로 진입할수록 증가하는 특징이 나타났다. 구역별 평균체류시간 변화를 운영 전과 운영 중으로 비교하면 운영 전에 비해 운영 중에 가장 외해에 위치한 지역에서는 증가하고 나머지 구역에서는 감소하였다. 조력발전소 운영에 의한 인위적인 배수는 가장 외해에 위치한 지역에서 와동(vortex) 형성으로 입자 정체를 유발하였고, 나머지 지역에서는 연행작용(entrainment)을 발생시켜 체류시간의 변화에 영향을 주었다. 즉, 배수 시 발생하는 제트류(jet flow)와 와동, 연행작용으로 인한 체류시간 변화는 외해와 내만의 수평적 혼합 증가를 보여준다.

• 한국식생활문화학회지
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• 제36권4호
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• pp.349-361
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• 2021

This study was conducted to investigate the dietary adaptation and use of the university foodservice (UF) in Korea according to the residence period of foreign students. The average length of residence in Korea of t he subjects was 8.2 months. The period of residence was divided into quartiles: 1-4 months in the first quartile (average 2.2 months), 5-7 months in the second quartile (average 6.3 months), 8 months in the third quartile, and 9-66 months in the fourth quartile (average 18.3 months). The regularity of meals tended to be the highest in the 1st quartile and lowest in the 2nd quartile and then increased in the 3rd and 4th quartiles. The frequency of consumption of delivery food and convenience store food was lowest in the first quartile and highest in the second quartile and then decreased with the period of residence. The frequency of night eating increased according to the period of residence after the second quartile. The degree of adaptation to Korean foods was highest in the first quartile. The use of the university cafeteria was significantly higher in the 1st and 4th quartiles than in the 2nd and 3rd quartiles (p<0.05, p<0.01, respectively). The satisfaction with the UF decreased as the residence period increased. Based on these results, since international students are very positive and try to adapt to the dietary life in Korea in their early years of studying in Korea, it would be desirable to intensively support them to adjust to their dietary life at this time. In addition, since it takes about 18 months or more to assimilate the Korean food culture and show positive changes, it is necessary to continuously operate the Korean food culture adaptation program for international students over this period.

• 한국전산유체공학회지
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• 제21권2호
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• pp.106-111
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• 2016

Waste-to-energy facilities including incinerators are known as an efficient method to reduce wastes. In waste-to-energy facilities, more efficient cooling system is still needed for grates as the energy density of waste increased. For better cooling performance with the water-cooled grates, optimal design of cooling water pathways is highly beneficial. We performed numerical investigation on fluid flow and residence time of cooling water with change of the geometry of the cooling water pathway. With addition of round shaped guide vanes in the water pathway, the maximum residence time of flow is reduced(from 4.3 sec. to 2.4 sec.), but there is no significant difference in pressure drop between inlet and outlet, and average residence time at the outlet. Furthermore the flow stagnation region moves to the outlet, as the position of the round shaped guide vanes is located to the neck point of pathways.

• 해양환경안전학회지
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• 제22권1호
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• pp.20-26
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• 2016

해역에서의 체류시간은 제한된 영역을 채우는 수체나 오염물질이 잔류하는 시간을 의미하며, 서로 다른 수체간의 물리적 특성을 비교하는 데 사용되고 있다. 거제만으로 유입되는 육상기원 또는 양식기원 입자물질의 잔류시간을 알아보기 위해 입자추적모델이 포함된 EFDC를 이용하여 입자물질 체류시간을 계산하였다. 계산된 입자물질의 체류시간은 내만에서 약 65일이었는데, 이 결과는 거제만 내측으로 유입되는 입자물질이 외해에 도달하기까지 약 2달 이상의 시간이 소요됨을 의미한다. 이 체류시간은 거제만 전역에 걸쳐 조석의 흐름에 따라 다르게 나타났으며, 해역에 유입된 입자물질의 거동이 해역의 물리적 특성에 의해 결정됨을 의미한다. 입자물질 체류시간의 공간적인 분포특성을 통해 거제 내만의 해수교환이 원활하지 않은 것을 알 수 있으며, 이로 인해 수질오염문제에 취약할 수 있다는 것을 알 수 있다.

• 해양환경안전학회지
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• 제17권4호
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• pp.339-343
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• 2011

본 연구에서는 EFDC모델과 입자추적모델을 이용하여 마산만의 담수유입에 의한 폐쇄성 내만의 물질체류시간을 산정하였다. 마산만의 해수유동을 재현하고 이를 바탕으로 평균체류시간을 계산하였다. 마산만의 조석에 의한 평균물질체류시간은 만 북측과 돝섬 부근까지가 약 110일이내, 모도 주변 해역이 약 40일, 부도에서 외해까지 약 20일 정도로 산정되었다. 담수유입에 따른 마산만의 4개 소해역별 평균물질체류시간은 I과 II영역에서 약 81일로 감소하였으나, 마산만의 외해측에 위치한 III과 IV영역은 각각 58일과 17일로 증가하였다.

• 한국환경과학회지
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• 제25권8호
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• pp.1087-1095
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• 2016

The concepts of residence time and flushing time can be used to explain the exchange and transport of water or materials in a coastal sea. The application of these transport time scales are widespread in biological, hydrological, and geochemical studies. The water quality of the system crucially depends on the residence time and flushing time of a particle in the system. In this study, the residence and flushing time in Gamak Bay were calculated using the numerical model, EFDC, which includes a particle tracking module. The average residence time was 55 days in the inner bay, and the flushing time for Gamak Bay was about 44.8 days, according to the simulation. This means that it takes about 2 months for land and aquaculture generated particles to be transported out of Gamak Bay, which can lead to substances accumulating in the bay. These results show the relationships between the transport time scale and physical the properties of the embayment. The findings of this study will improves understanding of the water and material transport processes in Gamak Bay and will be important when assessing the potential impact of coastal development on water quality conditions.