• 한국지하수토양환경학회지:지하수토양환경
• /
• 제17권3호
• /
• pp.39-48
• /
• 2012

Visual MODFLOW, a three dimensional groundwater flow model, was used to analyze effects of a weir construction in an alluvial stream on the nearby groundwater flow system. A hypothetical conceptual model was developed to investigate how the groundwater level and the water budget could change after a weir construction depending on the location of tributary streams. A site example, dealing with the Juksan weir installed in the Yeongsan River, was also demonstrated to predict the effects of the weir construction. Model results show that impacts of a weir construction on the groundwater flow system greatly vary depending on how far a tributary is located and whether it is located downstream or upstream from the weir. Therefore, consideration of the location of tributaries in planning the location of a weir could effectively minimize the impacts of a weir construction on the groundwater flow system. It is also demonstrated that model results are highly dependent upon how the model is dealing with small tributaries and agricultural drainage channels, which can be easily found nearby the main streams, acting as major water bodies for groundwater discharge. The model for the Juksan area shows that the weir construction will change the direction of groundwater flow in some areas, leading to changes of groundwater quality and interaction of the Yeongsan River to the aquifer from a gaining to a losing stream. The model also predicted the areas where rise of groundwater level caused by the Juksan weir could adversely affect plant growth, and thereby suggested installing new drainage channels as a countermeasure to drawdown the groundwater level.

• 한국유체기계학회 논문집
• /
• 제7권1호
• /
• pp.17-23
• /
• 2004

Aeroacoustic characteristics of sirocco fan used in Over-The-Range (OTR) has been analyzed in this paper. A microwave hood combination over the gas range is short for the OTR. The flow phenomena of the double-sided sirocco fan was analyzed numerically and experimentally by using commercial code and three dimensional PIV for flow visualization. Also, microphone array is used in order to understand acoustic characteristics of OTR. Two dimensional unsteady flow and acoustic simulation is tried to qualitatively estimate the effects of tonal noise and broadband noise on the overall sound pressure level. It is found that tonal sound is generated from the strong interaction between the impeller and cutoff while broadband sound is generated from the strong secondary flows along the scroll surface. To reduce the noise level, the V-shape cut-off was applied to improve the sound quality by reducing tonal noise. So the peak noise at BPF (Blade Passing Frequency) was almost reduced. The shape of flow-guide to suppress the secondary flow over the scroll surface was carefully checked. It is found that this affects flow pattern at the fan exit and reduces the broad band noise. Through this numerical and experimental study, the sound pressure level was lowered by 4dBA compared to that of the previous fan at the operating point.

• 융합정보논문지
• /
• 제12권4호
• /
• pp.278-285
• /
• 2022

본 연구는 VR 광고에서 현준감과 플로우 수준에 따라 광고태도와 기억정보의 유형인 속성 관련 기억정보와 종합적인 평가적 기억정보에 어떠한 영향을 미치는지를 살펴보는 것이다. 실험은 3X2 피험자간 요인설계로 진행되었다. 현대자동차 아이오닉 VR영상으로 진행되었고 143명의 피험자 설문지가 연구에 사용되었다. 연구 결과 감정적 현존감이 가장 높을 때 광고태도가 긍정적이었다. 또한 인지적 현존감이 기억에 미치는 영향은 플로우가 높을 때 제품 속성 정보 등의 ARM이 증가하였고 플로우 수준이 낮을 때는 GRM이 증가하는 것으로 나타났다. 플로우가 높을 때는 GRM이 증가하는 것이 확인되었지만 플로우가 낮을 때는 ARM이 증가하는 것이 확인되었다. 본 실험에서 사용된 가상현실 광고는 기존의 광고로 브랜드 현존하는 브랜도여서 사전태도가 연구 결과의 가외 변인으로 작용되어 연구 결과의 일반화에 부정적인 영향을 미쳤을 가능성이 있다. 이에 향후 연구에서는 가상의 브랜드로 실험을 진행하는 것이 바람직할 것이다.

• 정보학연구
• /
• 제3권3호
• /
• pp.135-152
• /
• 2000

본 연구는 온라인에서 Flow 경험 변수(도전감/숙련)와 인지된 지각위험, 관여도 나아가 구매의도 변수간의 관계와 구조를 파악해 보려는 시도로 진행된 되었다. LISREL분석을 통한 분석결과는 소비자의 온라인 Flow 경험변수인 숙련도와 지각위험 간에는 부(-)의 관계를 나타냈으며, 숙련도와 관여도 간에는 정(+)의 관계를, 도전감과 관여도간의 관계는 정(+)의 관계를 보였다. 뿐만 아니라 지각위험과 관여도간의 관계는 부(-)의 관계를 나타냈으며, 지각위험과 구매의도, 관여도와 구매의도 간의 관계는 각각 부(-)와 정(+)의 관계로 나타났다. 이들 변수간의 관계와 구조를 파악한 것은 온라인소비자의 구매행동을 이해하고 전략적으로 대응하기 위한 마케팅활동에 매우 유용한 정보를 제공한다.

• 한국습지학회지
• /
• 제14권2호
• /
• pp.289-301
• /
• 2012

조석의 영향에 의해 해수의 유 출입이 용이한 해수호수를 친수 친환경으로 조성하는 계획이 인천 송도에서 수행되었다. 본 연구는 조석의 영향을 받는 해수호수의 수리동역학적 거동을 분석하기 위해서 1차원 수치모형인 CEA모형과 2차원 수치모형인 FLOW2DH를 이용하여 수로의 폭에 따라서 변화하는 해수호수 내의 수위 및 유속을 계산하였다. 연구 결과, CEA모형을 이용하여 수로의 적정 폭은 100.0m로 선정되었고, 외해 조위와 인공호수 수위의 지체시간과 수로 내 최대 유속이 계산하였다. 이 결과를 FLOW2DH와 연동하여 해수호수 내의 수위 및 유속을 각각 선정된 관측점에 대하여 비교 분석하였다. 또한, 인공호수의 유지관리 측면에서 수문이 설치된 경우에 대하여 수치모형 실험을 추가하여 수문이 설치되지 않은 경우보다 유속이 창조 시 약 20%, 낙조 시 약 50% 감소하는 효과를 얻었다.

• 한국해양공학회지
• /
• 제25권3호
• /
• pp.19-27
• /
• 2011

In case of constructing submerged breakwaters for the purpose of preventing coastal erosion, the number of submerged breakwaters, as well as their asymmetry is dependent on the field conditions. The aim of the present study was to examine the 3-D hydrodynamic characteristics (3-D wave field, wave height, mean water level, and mean flow) around the asymmetric submerged breakwaters using a 3-D numerical model, LES-WASS-3D, which was validated through a comparison with existing experimental data and showed fairly nice agreement. From the numerical results, the wave height, mean water level, and mean flow are discussed in relation with the variation in the breakwater length ratio.

• 한국전산유체공학회지
• /
• 제12권2호
• /
• pp.21-25
• /
• 2007

A general purpose program NUFLEX has been extended for two-phase flows with topologically complex interface and cavitation flows with liquid-vapor phase change caused by large pressure drop. In analysis of two-phase flow, the phase interfaces are tracked by employing a LS(Level Set) method. Compared with the VOF(Volume-of-Fluid) method based on a non-smooth volume-fraction function, the LS method can calculate an interfacial curvature more accurately by using a smooth distance function. Also, it is quite straightforward to implement for 3-D irregular meshes compared with the VOF method requiring much more complicated geometric calculations. Also, the cavitation process is computed by including the effects of evaporation and condensation for bubble formation and collapse as well as turbulence in flows. The volume-faction and continuity equations are adapted for cavitation models with phase change. The LS and cavitation formulation are implemented into a general purpose program for 3-D flows and verified through several test problems.

• Journal of Power Electronics
• /
• 제13권4호
• /
• pp.569-583
• /
• 2013

In this study, the simultaneous use of a multi-level converter (MLC) as a DC-motor drive and as an active battery cell balancer is investigated. MLCs allow each battery cell in a battery pack to be independently switched on and off, thereby enabling the potential non-uniform use of battery cells. By exploiting this property and the brake regeneration phases in the drive cycle, MLCs can balance both the state of charge (SoC) and temperature differences between cells, which are two known causes of battery wear, even without reciprocating the coolant flow inside the pack. The optimal control policy (OP) that considers both battery pack temperature and SoC dynamics is studied in detail based on the assumption that information on the state of each cell, the schedule of reciprocating air flow and the future driving profile are perfectly known. Results show that OP provides significant reductions in temperature and in SoC deviations compared with the uniform use of all cells even with uni-directional coolant flow. Thus, reciprocating coolant flow is a redundant function for a MLC-based cell balancer. A specific contribution of this paper is the derivation of a state-space electro-thermal model of a battery submodule for both uni-directional and reciprocating coolant flows under the switching action of MLC, resulting in OP being derived by the solution of a convex optimization problem.

• 한국농공학회지
• /
• 제34권1호
• /
• pp.87-99
• /
• 1992

A mathematical model, UNSATR which predicts the seepage flow through the body of dike especially under the tidal fluctuation has been developed. This model has been revised from UNSAT2 model which was developed on the basis of the saturated-unsaturated theory by Neuman. UNSATR has been verified and applied to the hydraulic model in order to estimated the seepage quantity, the formation of free water surface etc. The results lead to the following conclusions : 1. Seepage rates between the mathematical model and hydraulic model experiment are very similar to each other both in constant and transient water level conditions. 2. The lapsed time to be steady state of the free water surface becomes late as the tidal levels are relatively low mainly due to the seepage flow from the unsaturated zone of the body of dike. 3. Under the transient state of water levels, owing to the flow from the unsaturated domain, streamlines crossing to the free water surface are found and time lag during a falling tide may allow the free water surface inside the body of dike to stand at a high level than the outside water level. 4. The utility and validity of UNSATR model are convinced when the analyses on seepage problems through the porous embankment of the soil structures on the conditions of the steady and unsteady states are carried out.

• 한국농공학회지
• /
• 제40권5호
• /
• pp.43-51
• /
• 1998

In design and management of sea0dikes, engineers need to study various transient seepage conditions through dikes not only for the sea water infiltration into dikes due to cyclic rises of sea water level also for the seepage flow out from dikes toward the sea due to cyclic drawdown of sea water level. Characteristics of seepage flow toward the sea from dikes are more complicated than as known and remained unclearly. The case of such seepage flow may be explained by figuring out seepage characteristics in filter as a part of sea-dikes. Filters in most sea-dikes in Korea are inevitably placed with reversely inclined shape due to field construction conditions. Most computer programs for seepage analysis based on the various numerical methods give practically acceptable results, but for the case of reversely inclined section of filters any verification to apply them might be needed. In this study, large scaled model tests were executed to verify and understand seepage flow through earth-filled sea-dikes. The results from numerical analysis and model tests show some remarkable differences in pore pressure distribution under cyclic changes of see level, and some of the results need to be considered in design and construction practices with further study.