• Journal of the Korean Society of Visualization
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• v.15 no.3
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• pp.47-51
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• 2017

In this study, we investigate the wake characteristics in laminar inflow and two different turbulent inflow cases. To solve the flow with wind turbines and its wake, we use large eddy simulation (LES) technique with actuator line method (ALM) and turbulent inflow of Turbsim. We perform the quantitative analysis of velocity deficit and turbulent intensity in laminar inflow case and turbulent inflow case with different turbulent intensity. In turbulent inflow, unsteady strong wake recovery which is highly fluctuated in time. Normalized power in turbulent inflow case is also highly fluctuated with unsteady wake recovery, while that in laminar inflow has quasi steady characteristic in power generation.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.109-116
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• 1999

This study is to make clear for the characteristics of radial drainage consolidation/permeability At the result of the radial drainage consolidation / permeability test, the permeability of outflow drainage condition is higher than Inflow drainage condition and the time for the end of consolidation, outflow drainage condition is shorter than inflow drainage condition. So drainage area ratio test and control of hydraulic gradient test are carry out to analysis this result. Finally, compared with the characteristics on the condition of inflow and outflow permeability and consolidation.

• Journal of the Korean Society of Visualization
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• v.14 no.3
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• pp.28-31
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• 2016

In this study, we investigate the wake characteristics in two cases which are laminar inflow and turbulent inflow. To solve the flow with wind turbines and its wake, we use large eddy simulation (LES) technique with actuator line method (ALM) and turbulent inflow of Turbsim. Turbulent inflow which contains the characteristic of the stable atmospheric boundary layer is used. We perform the quantitative analysis of velocity deficit and turbulence intensity in two cases. Time series of velocity deficit at the first, the second column in two cases are compared to observe the performance of wind turbine. The performance in the first column in laminar inflow is overestimated compared to that in turbulent inflow. And we observe that wake in the case with turbulent inflow drive to the span-wise direction and wake recovery in turbulent inflow is more effective. In quadrant analysis of Reynolds stress, the ejection and the sweep motion in turbulent inflow case are bigger than those in laminar inflow case.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.3
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• pp.95-105
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• 2018

Understanding the composition of the dam inflow can improve the efficiency of dam operation considering the seasonal characteristics. Hydrograph analysis is one of the methods to identify the characteristics of dam inflow. In addition, baseflow separation on the dam inflow can be affected by anthropogenic influences depending on dam locations. In this regard, the objectives of this study are 1) to analyze yearly and monthly baseflow contribution to the dam inflow and 2) to compare the baseflow contribution to the inflow in dams located upstream and downstream of the watershed. The result shows that the estimated baseflow index was smaller in the upstream dams compared to the downstream dams. Discharge from the upstream water infrastructure including dams and reservoirs can be a part of inflow into the downstream water infrastructure. Based on this scenario, the discharge regulated from the upstream dam could lead to overestimation of baseflow contribution to inflow into the downstream dam. We expect that the results from this study elucidate the role and function of dams and hence, contribute to the efficient operation of dams located in the upstream and the downstream of the watershed.

• Wind and Structures
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• v.5 no.2_3_4
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• pp.209-226
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• 2002

When predicting unsteady flow and pressure fields around a structure in a turbulent boundary layer by Large Eddy Simulation (LES), velocity fluctuations of turbulence (inflow turbulence), which reproduce statistical characteristics of the turbulent boundary layer, must be given at the inflow boundary. However, research has just started on development of a method for generating inflow turbulence that satisfies the prescribed turbulence statistics, and many issues still remain to be resolved. In our previous study, we proposed a method for generating inflow turbulence and confirmed its applicability by LES of an isotropic turbulence. In this study, the generation method was applied to a turbulent boundary layer developed over a flat plate, and the reproducibility of turbulence statistics predicted by LES computation was examined. Statistical characteristics of a turbulent boundary layer developed over a flat plate were investigated by a wind tunnel test for modeling the cross-spectral density matrix for use as targets of inflow turbulence generation for LES computation. Furthermore, we investigated how the degree of correspondence of the cross-spectral density matrix of the generated inflow turbulence with the target cross-spectral density matrix estimated by the wind tunnel test influenced the LES results for the turbulent boundary layer. The results of this study confirmed that the reproduction of cross-spectra of the normal components of the inflow turbulence generation is very important in reproducing power spectra, spatial correlation and turbulence statistics of wind velocity in LES.

• The Journal of Engineering Geology
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• v.11 no.2
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• pp.141-152
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• 2001

The waterway tunnel zone (length 1,484m) in the Hyeonseo-myeon area that is a part of Yeongcheon dam waterway tunnel has been studied to characterize the relationship between groundwater inflow into the waterway tunnel and hydrogeologic characteristics. The effects of sandstone thickness in the tunnel section. fracture density, fracture aperture and spacing, fault zone width and hydraulic conductivity on the early inflow (inflow prior to the lining and grouting) are investigated. The relationship between fracture density and hydraulic conductivity is also considered. The result of the study suggests that fault zone width has the greatest effect on groundwater inflow into the tunnel, and sandstone thickness, hydraulic conductivity and fracture density in order shows an influence on the inflow.

• Wind and Structures
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• v.19 no.2
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• pp.219-232
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• 2014

The characteristics of turbulent boundary layers over hilly terrain depend strongly on the hill slope and upstream condition, especially inflow turbulence. Numerical simulations are carried out to investigate the neutrally stratified turbulent boundary layer over two-dimensional hills. Two kinds of hill shape, a steep one with stable separation and a low one without stable separation, two kinds of inflow condition, laminar turbulent, are considered. An auxiliary simulation, based on the local differential quadrature method and recycling technique, is performed to simulate the inflow turbulence be imposed at inlet boundary of the turbulent inflow, which preserves very well in the computational domain. A large separation bubble is established on the leeside of the steep hill with laminar inflow, while reattachment point moves upstream under turbulent inflow condition. There is stable separation on the side of low hill with laminar inflow, whilw not turbulent inflow. Besides increase of turbulence intensity, inflow can efficiently enhance the speedup around hills. So in practice, it is unreasonable to study wind flow over hilly terrain without considering inflow turbulence.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.4
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• pp.428-434
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• 1999

Experimental studies on the characteristics of annular jet pump were carried out in this paper. Jet pump can be used widely for the transportation of solid materials, farm produce and fishes. The effects of high pressure chamber on the characteristics of annular jet pump were sought in this paper. Experiments were done for three shapes of high pressure chamber, and for several lengths of the high pressure chamber. Three types of the high pressure chamber's entrances($90^{\circ}$ single inflow, $45^{\circ}$single inflow, and $45^{\circ}$ double inflow) were tested. Water was used for both the primary fluid and secondary fluid. The results obtained in this study are as follows; $45^{\circ}$double inflow type is the most effective among the tested three types of the high pressure chamber's entrances. The efficiency of jet pump with 400mm of high pressure chamber length is the highest among the chamber lengths tested in this study, thus indicating appropriate chamber length is required to get an efficient.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.75-81
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• 2000

Experimental studies on the characteristics of annular jet pump were carried out in this paper. The effects of high pressure chamber on the characteristics of annular jet pump were sought in this paper. Experiments were done for three shapes of high pressure chamber, and for several lengths of the high pressure chamber. Three types of the high pressure chamber's entrances($90^{\circ}$ single inflow, $45^{\circ}$ single inflow, and $45^{\circ}$ double inflow) were tested. Water was used for both the primary fluid and secondary fluid. The results obtained in this study are as follows; $45^{\circ}$ double inflow type is the most effective among the tested three types of the high pressure chamber's entrances. The efficiency of jet pump with 400mm of high pressure chamber length is the highest among the chamber lengths tested in this study, thus indicating appropriate chamber length is required to get an efficient jet pump.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.671-680
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• 2003

The accuracy of inflow into tunnel estimates depends largely on how well permeability is characterized. But, the average of the packer test results will always underestimate the upper end of the permeability range, and therefore underestimate the inflow. Taking an average of the test results always underestimates inflow because the average permeability does not really exist. The distribution of packer-test data may not accurately reflect permeability, however, due to the limits of the test method and the luck of the field investigation. These discrepancies may be overcome by using Raymer(2001)'s log-normal plots and Heuer(1995)'s histograms of the data to develop a permeability model that will be used in lieu of the data to calculate inflow. Furthermore, the influence on the inflow is examined by the geological characteristics based upon the hundred times of packer test OO tunnel project.