• Title/Summary/Keyword: Natural Circulation

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Impacts of wave and tidal forcing on 3D nearshore processes on natural beaches. Part I: Flow and turbulence fields

  • Bakhtyar, R.;Dastgheib, A.;Roelvink, D.;Barry, D.A.
    • Ocean Systems Engineering
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    • v.6 no.1
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    • pp.23-60
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    • 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.

Impacts of wave and tidal forcing on 3D nearshore processes on natural beaches. Part II: Sediment transport

  • Bakhtyar, R.;Dastgheib, A.;Roelvink, D.;Barry, D.A.
    • Ocean Systems Engineering
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    • v.6 no.1
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    • pp.61-97
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    • 2016
  • This is the second of two papers on the 3D numerical modeling of nearshore hydro- and morphodynamics. In Part I, the focus was on surf and swash zone hydrodynamics in the cross-shore and longshore directions. Here, we consider nearshore processes with an emphasis on the effects of oceanic forcing and beach characteristics on sediment transport in the cross- and longshore directions, as well as on foreshore bathymetry changes. The Delft3D and XBeach models were used with four turbulence closures (viz., ${\kappa}-{\varepsilon}$, ${\kappa}-L$, ATM and H-LES) to solve the 3D Navier-Stokes equations for incompressible flow as well as the beach morphology. The sediment transport module simulates both bed load and suspended load transport of non-cohesive sediments. Twenty sets of numerical experiments combining nine control parameters under a range of bed characteristics and incident wave and tidal conditions were simulated. For each case, the general morphological response in shore-normal and shore-parallel directions was presented. Numerical results showed that the ${\kappa}-{\varepsilon}$ and H-LES closure models yield similar results that are in better agreement with existing morphodynamic observations than the results of the other turbulence models. The simulations showed that wave forcing drives a sediment circulation pattern that results in bar and berm formation. However, together with wave forcing, tides modulate the predicted nearshore sediment dynamics. The combination of tides and wave action has a notable effect on longshore suspended sediment transport fluxes, relative to wave action alone. The model's ability to predict sediment transport under propagation of obliquely incident wave conditions underscores its potential for understanding the evolution of beach morphology at field scale. For example, the results of the model confirmed that the wave characteristics have a considerable effect on the cumulative erosion/deposition, cross-shore distribution of longshore sediment transport and transport rate across and along the beach face. In addition, for the same type of oceanic forcing, the beach morphology exhibits different erosive characteristics depending on grain size (e.g., foreshore profile evolution is erosive or accretive on fine or coarse sand beaches, respectively). Decreasing wave height increases the proportion of onshore to offshore fluxes, almost reaching a neutral net balance. The sediment movement increases with wave height, which is the dominant factor controlling the beach face shape.

An evaluation of the composition and elements in Korean traditional interior space - On Choosa-Gotack in the Chosun dynasty - (한국전통 실내공간의 구성방법과 요소 분석을 통한 의미 고찰 - 조선조 추사고택을 중심으로 -)

  • 천진희
    • Archives of design research
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    • no.16
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    • pp.101-110
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    • 1996
  • CHOOSA GORACK which is a typical example of traditional houses in the CHO SEON dynasty consists of the four terraced builfing group. Among those,SADANG CHAI are located in the highest level,and SADANG CHAI and SADANG CHAI are toward south direction.It means that building orientation and level were influenced by the distinction of social level and the idea of ancester worship. Floor and ceiling level in the same building is different which was caused by the distinetion of social level in the CHO SEON dynasty and an ariental dual as a variety of openings,exposed ceilings,and furniture against a wall were creating a typical Korean visual harmony. Although the furniture and equipments were very important elements in ONDOL BANG the occupance ratio of these were low because the free space in BANG should be utilized effectively to accommodate the space variation.Both an AN CHAI and SARANG CHAI were composed by the standard space module called KAN.And interior elements were established by several factors such as the human scale,the behavior pattern in traditional sitting life style, and the lumber size of post and lintel construction of Korean house.BANG and DAE GHUNG, composed of KAN,were expanded and arranged side by side so that the natural light and ventilation through them could be used in the result of the kind of lay out,traffic circulation was disturved.In conclusion,CHOOSA GOTACK was formed by the sirect effice of the KOREAN penisula. However this study was based on one sample. It may not enough to deduct soild conclusion.Therefore continuous and farher study is needed for the sestemane evaluation.

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Evaluation of Left Ventricular Assist Device through In Vivo Experiments (생체실험을 통한 좌심실보조기의 평가)

  • Park, Seong-Keun;Won, Yong-Soon;Jung, Pil-Sup;Choi, Jin-Wook;Kim, In-Young;Lee, Kyu-Baek;Min, Byoung-Goo
    • Proceedings of the KOSOMBE Conference
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    • v.1993 no.11
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    • pp.89-92
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    • 1993
  • In this article, we present and analyze the results of the three consecutive in vivo experiments of the LVAD to evaluate the function of the LVAD and the adverse effects on living animals. We applied the LVAD consecutively to three mongrel dogs and the circulation of the blood was assisted under the anesthesia. We used in general both the asynchronous mode and the synchronous mode to drive the LVAD. During the experiments we monitored the dogs with a polygraph to evaluate the function of the LVAD and the additional effects on the natural hearts. We also examined several clinical pathologic tests in order to see the effects of the LVAD to the red blood cells and the other internal organs. The dogs survived for two to there days. The LVAD assisted the circulatory system at the maximum assist flow rate of 3.0 1/min. Although the red blood cells of the dogs had mechanical damages by the LVAD to result in the hemolysis, the degree of the hemolysis was not so high and the damages caused by the hemolysis on the dogs were not serious. The myocardium of the first dog was gradually worsened and eventually failed. The damage of the myocardium was due to the asynchronous driving mode of the LVAD. The other organs did not have serious damages due to the application of the LVAD. The main purpose of this paper is to evaluate the results of the in vivo experiments of the LVAD and to find better ways to the application of the LVAD to human beings.

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Effect of Application Level of Swine Slurry on Production and Nutritive Value of Rye (돈분액비 시용수준이 호밀의 수량 및 사료가치에 미치는 영향)

  • 임영철;윤세형;김종근;김원호;김맹중;신재순;정의수;이종경;신동은
    • Journal of The Korean Society of Grassland and Forage Science
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    • v.23 no.4
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    • pp.293-298
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    • 2003
  • Livestock manure have been utilized as fertilizer, and trying to make resources natural circulation of organic materials. This experiment was carried out to investigate the effect of swine slurry on production and nutritive value of rye, and to determine optimal application level for 2 years from Oct. 2000 to May 2002 in the experimental field of Grassland and Forage Crops Division, National Livestock Research Institute. Summary of the results were as follows. The application of swine slurry 200% Plot showed the best regrowth after winter and lodging was severe in all plots except non-fertilized plot. Plant height was lower in lodging plots. The dry matter yield was not significantly difference between chemical fertilizer(CF) plot and swine slurry application plots, and swine slurry 100% + CF 50% plot showed the highest yield among manure application plots. The dry matter yield per input nitrogen was 80kg in CF, 81kg in swine slurry 100% application plot. Above the level, it was decreased severely by 41 ∼ 61kg. Conclusively, application to swine slurry 100% showed superior productivity considering the DM yield per input nitrogen, That level would be recommended to produce higher yield and to conserve environment.

A Study on Conservation and Management of the Joseon Royal Tomb's System - Focused on Joseon Royal Tombs of Middle District in Seoul - (조선왕릉의 능제보존관리에 관한 연구 - 서울 중부지구 조선왕릉을 중심으로 -)

  • Choi, Jong-Hee;Lee, Chang-Hwan;Hwang, Kyu-Man;Kim, Kyu-Yeon
    • Journal of the Korean Institute of Traditional Landscape Architecture
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    • v.35 no.4
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    • pp.43-55
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    • 2017
  • The purpose of this study is to investigate conservation and management methods of the Joseon Royal Tombs in the Middle District. Urbanization has damaged many of the original terrains as many buildings and facilities have entered the inner and outer area of Joseon Royal Tombs. Land purchase, relocation and demolition of the building are required for the recovery of the Royal Tombs area, and then it is necessary to recover the original terrain. In the case of land use and pathways, there were many land use which harmed the sacred atmosphere of the area, and many disconnection of the ritual circulation, they should be maintained to remind the sacred atmosphere of the royal tomb. The water system should be changed to natural type canal, and it is necessary to collect accurate information on the lost buildings and stoneworks through literature survey and excavation investigation, and then lead to the exposure or restoration of the ruins. Historical forests require periodic and ongoing monitoring and management, and it is necessary to establish a historical and cultural museum that can provide to visitors information about Joseon Royal Tombs. These works should be classified into short, medium and long-term projects with a long perspective to implement continuous and systematic projects.

Analysis of Loss of Offsite Power Transient Using RELAP5/MODl/NSC; I: KNU1 Plant Transient Simulation (RELA5/MOD1/NSC를 이용한 원자력 1호기 외부전원상실사고해석 - I. 실제사고해석)

  • Kim, Hho-Jung;Chung, Bub-Dong;Lee, Young-Jin;Kim, Jin-Soo
    • Nuclear Engineering and Technology
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    • v.18 no.2
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    • pp.97-106
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    • 1986
  • System thermal-hydraulic parameters and simulated, using the best-estimate system code(RELAPS/MODl/NSC), based upon the sequence of events for the KNU1 (Korea Nuclear Unit 1) loss of offsite power transient at 77.5% power which occurred on June 9,1981. The results are compared with the actual plant transient data and show good agreements. After the flow coastdown following the trips of both reactor coolant pumps, the establishment of natural circulation by the temperature difference between the hot and the cold legs is confirmed. The calculated reactor coolant flowrate closely approximates the plant data indicating the validity of relevant thermal-hydraulic models in the RELAP5/MOD1/NSC. Results also show that the sufficient heat removal capability is secured by the appropriate supply of the auxiliary feedwater without the operation of S/G PORVs. In addition, a scenario accident at full power, based upon the same sequence of events described above, is also analysed and the results confirmed that the safety of KNU1 is secured by the appropriate operation of the S/G PORVs coupled with the supply of auxiliary feedwater which ensures sufficient heat removal capability. The characteristics of the non-safety related components such as the turbine stop valve closing time, S/G PORV settings etc. are recognized to be important in the transient analyses on a bestestimate basis.

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Effect of Tourmaline-added Eyeglass Frames on Normalization of Intraocular Pressure (토르말린이 첨가된 안경테가 안압 정상화에 미치는 영향)

  • Park, Sang-Chul;Jeong, Hye-Ri;Kwon, Jong-Moon;Lee, Gyu-Bin
    • The Korean Journal of Vision Science
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    • v.20 no.4
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    • pp.461-468
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    • 2018
  • Purpose : Tourmaline, a natural ore material, was applied to the entire eyeglasses to observe changes in intraocular pressure (IOP), one of the factors related to human ocular metabolism. Methods : After making eyeglass frames by mixing TR-90, which is the main material of eyeglass frames and 7wt% of tourmaline, The changes of intraocular pressure before and after wearing of tourmaline spectacle frames were divided into low, middle and high groups according to the intraocular pressure in 90 normal subjects (46 men and 44 women) in their 20s. Results : Total intraocular pressure was a significantly decreased to -4.14% (p<0.000) in the right eye after wearing tourmaline frames, and significantly decreased to -6.39 % (p<0.000) and -4.64 % (p<0.017) in the High and Middle groups, respectively. Total intraocular pressure was a significantly decreased to -2.74 % (p<0.004) in the left eye, and -4.58 % (p<0.000) in the High group only showed statically significant value. Conclusion : In this study, the spectacle frame containing 7wt% tourmaline was used and it was confirmed that the intraocular pressure was significantly decreased after wearing the spectacle frame, and it became close to the average value of the normal intraocular pressure range. The results of this study showed that tourmaline, which has the effect of promoting the metabolism and blood circulation of the body, has an effect on the normalization of the intraocular pressure by attaching it to the spectacle frame.

Assessment of Water Circulation and Hydro-characteristics with LID techniques in urbanized areas (도시지역에 적용된 LID 기법의 강우시 수문특성 및 물순환 평가)

  • Choi, Hyeseon;Hong, Jungsun;Jeon, Minsu;Geronimo, Franz Kevin;Kim, Leehyung
    • Journal of Wetlands Research
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    • v.21 no.3
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    • pp.191-198
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    • 2019
  • High impervious surfaces increase the surface runoff during rainfall and reduces the underground infiltration thereby leading to water cycle distortion. The distortion of water cycle causes various urban environmental problems such as urban flooding, drought, water pollutant due to non-point pollution runoff, and water ecosystem damage. Climate change intensified seasonal biases in urban rainfall and affected urban microclimate, thereby increasing the intensity and frequency of urban floods and droughts. Low impact development(LID) technology has been applied to various purposes as a technique to reduce urban environmental problems caused by water by restoring the natural water cycle in the city. This study evaluated the contribution of hydrologic characteristics and water cycle recovery after LID application using long-term monitoring results of various LID technology applied in urban areas. Based on the results, the high retention and infiltration rate of the LID facility was found to contribute significantly to peak flow reduction and runoff delay during rainfall. The average runoff reduction effect was more than 60% at the LID facility. The surface area of the LID facility area ratio(SA/CA) was evaluated as an important factor affecting peak flow reduction and runoff delay effect.

Analysis the Use of Concrete Fine Aggregates of Coal Gasification Slag (콘크리트용 잔골재로서 석탄가스화 용융슬래그(CGS)의 활용성 분석)

  • Park, Kyung-Taek;Han, Min-Cheol;Hyun, Seung-Yong
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.7 no.2
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    • pp.101-108
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    • 2019
  • This study is analysis of the utilization as a concrete fine aggregate on CGS, a by-product of Integrated coal gasification combined cycle(IGCC). That is, in KS F 2527 "Concrete aggregate," properties of 1~12times to CGS were evaluated, focusing on quality items corresponding to natural aggregate sand(NS) and melted slag aggregate sand(MS). As a result, the distribution of grain shape, safety and expansion were all satisfied with KS standards by physical properties, but the quality was unstable at 7~12times of water absorption ratio and absolute dry density. The particle size distribution was unstable due to asymmetry distribution of coarse particles, and particles were too thick for 7~12times. The passing ratio of 0.08mm sieve was also out of the KS standard at part factor of 7~12times, but chloride content, clay contents, coal and lignite were all satisfactory. Meanwhile, chemical composition was satisfactory except for $SO_3$ in 1~6times, and content and amount of harmful substances were all within the specified value except for F in 7~12times. As a result of SEM analysis, the surface quality and porosity were 7~12times more than 1~6times, and it was the quality was degraded. Therefore, it is necessary to reduce the quality deviation by using separate measures in order to utilize it as concrete aggregate in the future, and if it is premixed with fine quality aggregate, it will contribute positively to solve aggregate supply shortage and utilize circulation resources.