• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.564-565
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• 2012

• Proceedings of the SAREK Conference
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• 2003.07a
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• pp.7-7
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• 2003

• Magazine of the Korea Institute for Structural Maintenance and Inspection
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• v.20 no.2
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• pp.46-51
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• 2016

• Journal of computational fluids engineering
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• v.19 no.3
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• pp.85-90
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• 2014

The purpose of this study is to develop a new Meshless Method to solve 2-D compressible flow problems numerically. This paper includes a revised Least Square method that improves robustness compared with its original version by removing excessive numerical oscillation which occurs when points are randomly distributed. Numerical analyses of hypersonic flow over a blunt body were carried out using the method, then robustness, accuracy and convergence of their results were compared with those obtained from the original method.

• The Journal of Engineering Geology
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• v.3 no.2
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• pp.149-165
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• 1993

Nowadays, the field hydraulic test is still an only method to evaluate groundwater characteristics in subsurface. The results of hydraulic test are very important for the concept model of fracture hydrogeology as well as the geometric pattern of fractures. The hydraulic tests performed in Korea are generally analysed under such assumption as steady radial flow in homogeneous aquifer or along simple geometry of fractures. Also the transmissivity measured in a fixed interval length is equivalent to a sum of individual fracture transmissivities in test legth. The boundary effects of weH hydraulics and the geometry of flow paths are hardly obtained from the test results analysed by a steady flow method. To circumvent this problem, the flow dimensional analysis was attempted from the results of constant pressure injection test carried out in a fractured granite area. A comparison of the hydraulic conductivity values from the transient and steady analysis shows that the latter is about a factor of 2~3 higher than the former. However, it was possible to analyse a flow dimension of each test interval from flow rate variation with time. The upper part of the bedrock(<10m deep) indicates an open boundary and the flow dimension shows nearly steady states, while the lower part of the bedrock(>25m deep) is characterized as sublinear flow dimension with a dosed boundary. In one of the test sections(15m deep), the flow dimension was changed from linear flow to spherical flow. From the experience of this study, one of the immediate problems to be solved is to enhance the field testing equipments, i.e., an accurate flowmeter with autorecording and a pressure detecting device to be able to install in the test section.

• Journal of Power System Engineering
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• v.14 no.2
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• pp.5-11
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• 2010

분사연료의 혼합기형성과정 최적화를 통한 연소제어 기술은 디젤기관의 기관운전 및 배기특성을 향상시키기 위하여 매우 중요하다. 또한 분무의 혼합기형성 최적화를 위해서는 분사된 연료와 주위기체와의 혼합과정에 영향을 미치는 분무내부의 유동특성에 대한 연구는 필수 불가결하다. 따라서 본 연구에서는 고온 고압의 증발장에서 분무의 액상 거동에 주목하고, 그 거동특성을 통하여 증발디젤분무의 혼합기형성을 해석한다. 비정상 증발분무의 중심축에 레이저 시트광을 입사한 후, 액상분무 액적의 Mie 산란광에 의한 2차원 화상을 획득하여 증발분무 액상의 속도분포 및 와도(vorticity) 등을 구하였다. 분무의 속도분포 및 와도는 2차원 화상에 PIV법을 적용하여 계산하였다. 그림 1에 본 연구에서 구한 속도분포의 일례를 보인다. 본 연구의 결과로 상변화를 동반하는 비정상 증발장에서 구한 분무액상의 거동 특성은 상변화가 일어나지 않는 비증발장에 있어서의 분무거동특성과 유사함을 확인하였다.

• The Journal of Engineering Geology
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• v.30 no.2
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• pp.131-145
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• 2020

The construction on these flimsy ground, activation of unsymmetrical surcharges, can often cause of the embankment road lateral flow or the destruction of the activities. In this study, the stability of the abutment pile foundation installed on soft ground and its behavior has been evaluated. The behavior of the abutment pile foundation under lateral flow was studied by verifying the behavior and reinforcement effects of the abutment pile foundation of previous studies about horizontal loads acting on the pile due to the lateral flow of the ground by performing finite element analysis. As a result of the consolidation analyses, the undrained cohesion or the strength of the soft ground, was increased by about 1.1 to 1.8 times by the increase in the strength of the soft ground according to the degree of consolidation. It is deemed reasonable to use 3.8 cm of the allowable displacement both economically and constructively, but considering the importance of the structure and the uncertainty of the ground, measurement shall be carried out during construction and thorough safety management of the lateral flow should be done.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.2
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• pp.265-273
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• 2012

Anaerobic sewage treatment is drawing attentions due to high energy consumptions and sludge production associated with aerobic treatment. This study evaluates the treatment characteristics and energy balance of a fluidized bed reactor (FBR) for treating domestic sewage at $20^{\circ}C{\sim}25^{\circ}C$ for 245 days. Sewage fed to the FBR was a primary clarifier effluent of a domestic sewage treatment plant with COD of 99-301 mg/L and $BOD_{5}$ of 37-149 mg/L. Effluent $SBOD_{5}$ and its removal efficiency at HRT of 1~3 h were 6~15 mg/L and 73.4~85.5%, respectively, achieving high removal efficiency for soluble organic substances even at short HRTs. COD removal efficiency and its effluent concentration were 53.8~75.9% and 51~83 mg/L, respectively. The energy production potential from gaseous methane was 0.009-0.028 kWh/$m^{3}$, which satisfies the energy required for the FBR operation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.11
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• pp.559-566
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• 2015

The main objective of this work is to experimentally investigate the effect of angle variation on the distribution of two-phase flow at header-channel junctions. The cross-sections of the header and the channels were fixed at $16mm{\times}16mm$ and $12mm{\times}1.8mm$, respectively. Air and water were used as the test fluids. Four different header-channel positions were tested : Vertical header with Horizontal channels (case VM-HC), Horizontal header with Horizontal channels (case HM-HC), Horizontal header with Vertical Downward channels (case HM-VDC), and Horizontal header with Vertical Upward channels (case HM-VUC). In all cases, liquid flow distribution tended to decrease gradually in the upstream header region. However, in the downstream region, different trends could be seen. The reason for these different tendencies were identified by flow visualization in each case. The standard deviations for the liquid and gas flow distribution in each case were calculated, and the case of VM-HC had the lowest values compared to other cases because of the symmetrically distributed liquid film and strong flow recirculation near the end plate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.5
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• pp.313-319
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• 2016

It is very important to understand and control the sloshing in a liquid container that is partially filled with liquid. Previous studies focused primarily on the sloshing and resonance caused by sinusoidal excitations, while the present study focuses on understanding and suppressing sloshing in a container that moves rapidly from a given point to another in industrial applications. To achieve this, we first numerically predict the two-phase flow induced by the horizontal movement of a rectangular container. Then we analyze the effects of container-velocity profile (in particular acceleration/deceleration duration) on sloshing. Results show that sloshing is significantly suppressed when the acceleration/deceleration duration is a multiple of the 1st-mode natural period of sloshing.