• The Journal of Engineering Geology
• /
• v.27 no.1
• /
• pp.59-66
• /
• 2017

The characteristic of recent rainfall pattern in Korea is concentrated in summer season and it is very different compare with former characteristic. In 2011, there was heavy rainfall in Chuncheon city of northern part of Korea. Because of rainfall in short time, many landslides were occurred in narrow area and many people were killed by these landslides at that time. The purpose of this study is to calculate run-out distance of debris flow and analyze the movement properties of debris flow according to the elapsed time using numerical analysis method at that time. The debris 2D program, which is developed by prof. Liu in National Taiwan University, was used in this study. Run-out distance of debris flow was calculated under different yield strength conditions which were controlled by rainfall amount. The results reveal that absolute maximum velocity of the debris flow is about 8.1 m/s and maximum depth of debris flow is about 7 m when debris flow was occurred. The run-out distance after 500 sec is about 300 m from end of the valley. It is very well similar with actual debris flow run-out distance. From these results, we can presume the maximum velocity and depth of debris flow at that time.

• Journal of the Korean Geotechnical Society
• /
• v.39 no.5
• /
• pp.13-26
• /
• 2023

This study examined the soil-water characteristic curve (SWCC), considering the volume change, using wetting curves on the field monitoring data of a wireless sensor network. Special attention was given to evaluating the landslide vulnerability by deriving a matric suction suitable for the actual site during the wetting process. Laboratory drying SWCC and shrinkage laboratory tests were used to perform the combined analysis of landslide and debris flow. The results showed that the safety factor of the wetting curve, considering the volume change of soil, was lower than that of the drying curve. As a result of numerical analyses of the debris flow simulation, more debris flow occurred in the wetting curve than in the drying curve. It was also found that the landslide analysis with the drying curve tends to overestimate the actual safety factor with the in situ wetting curve. Finally, it is confirmed that calculating the matric suction through SWCC considering the volume change is more appropriate and reasonable for the field landslide analysis.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.18 no.3
• /
• pp.109-115
• /
• 2019

The purpose of this study was to analyze and test the flow rate of a 1-inch ball valve used in a thermal power plant. To identify the flow-rate characteristics, numerical analysis was conducted and an experimental apparatus of the valve flow rate coefficient was used to compare the flow coefficient Cv values. To determine the internal pressure distribution, the sites of opening ball valves and flow fields were investigated. In particular, a smaller the valve opening resulted in a more complicated the flow field of the ball. The valve flow characteristic test showed that the Cv value and flow rate increased with increasing valve-opening rate and the secondary function was performed. The pressure drop increased as the valve opening rate decreased. In addition, the experimental results for the flow analysis are similar to the numerical analysis results.

• 한국전산유체공학회:학술대회논문집
• /
• 2001.05a
• /
• pp.116-120
• /
• 2001

The impactive Pressure wave induced by pyro valve in the pressurization system of KSR-III may result in fatal failure or malfunction of valves, so it is important to know the pressure wave characteristic in the pressurization system. An unsteady flow analysis in the simplified pressurization system was peformed by Finite difference method.

• 한국전산유체공학회:학술대회논문집
• /
• 2009.11a
• /
• pp.170-176
• /
• 2009

Flow control butterfly valve(FCBV) is known to have difficulty in controlling flow rate along valve opening due to its high flow rate. In low opening condition, the butterfly valve also has some shortcomings such as noise, vibration and erosion which are mostly caused by cavitation effects. Therefore, the FCBV requires proper remedies to reduce cavitation effects and to improve flow control performance. Numerical analysis is applied to FCBV flow to find effects of design factors such as seat diameter and valve opening rate. Cases with 3 different sizes of seat diameter and various valve opening rate are selected for the numerical analysis. From the analysis results, it is found that the FCBV with small seat diameter shows better pressure loss performance and reduced cavitation effects.

• Journal of computational fluids engineering
• /
• v.15 no.1
• /
• pp.64-70
• /
• 2010

Flow control butterfly valve(FCBV) is known to have difficulty in controlling flow rate along valve opening due to its high flow rate. In low opening condition, the butterfly valve also has some shortcomings such as noise, vibration and erosion which are mostly caused by cavitation effects. Therefore, the FCBV requires proper remedies to reduce cavitation effects and to improve flow control performance. Numerical analysis is applied to FCBV flow to find effects of design factors such as seat diameter and valve opening rate. Cases with 3 different sizes of seat diameter and various valve opening rate are selected for the numerical analysis. From the analysis results, it is found that the FCBV with small seat diameter shows better pressure loss performance and reduced cavitation effects.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2003.05a
• /
• pp.240-244
• /
• 2003

In this paper, we present the CFD and experimental results for flow characteristics as well as pressure fluctuation in a T-type ball valve. In the experiment, flow visualization for the wake is performed with a fluorescent dye. In CFD, the valve flow is simulated three-dimensionally using a commercial fluid analysis code, FLUENT 6.0. FFT analysis to the pressure fluctuation in the wake region is also calculated Analysis results show that the characteristic frequency of the wake flow is strongly dependent on the Reynolds number.

• 한국전산유체공학회:학술대회논문집
• /
• 2010.05a
• /
• pp.315-319
• /
• 2010

The near wake of square section cylinders with different corner radii is studied by numerical method to investigate the influence of corner radius. Eight models, R/D=0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5 (R is the corner radius and D is the characteristic dimension of the body) at Re=500 were studied. The numerical results of St, CD and CL at R/D=0 and R/D=0.5 were compared with experiments to prove the feasibility and also investigate the trend of flow phenomena by the various radius corners. Results indicate that, as R/D ratio is increased, the Strouha lnumber is increased, the minimum pressure point on the cylinder surface moved own stream. The calculated results shows that between R/D=0.15 to R/D=0.3 have CD and CL.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.5
• /
• pp.99-107
• /
• 2003

Moisture flow and heat flow within pavement systems have been recognized as coupled processes with complex interactions between them. The distribution of moisture and temperature within pavement due to the moisture flow and heat flow varies not only seasonally but also vertically and horizontally. This paper presents an analysis model by the finite element method for the two-dimensional coupled moisture and heat flow in unsaturated soils. To test the model the analysis result by the model is compared with the analysis result by the software, GEO-SLOPE developed by GEO-SLOPE International Ltd. in Alberta, Canada. And a sensitivity analysis using ASTM method is performed to identify how model inputs affect the modeling analysis.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.9 no.4
• /
• pp.34-43
• /
• 2001

Analysis and control of intake charge motion such as swirl and tumble are very important to improve the performance of gasoline engines. In this paper, single frame double exposure PTV(particle tracking velocimetry) is used to investigate intake flow characteristic in a steady flow test rig of gasoline engine with 2-valve and pent-roof combustion chamber. To validate this PTV method, we confirmed reliability of this PTV method using chopper, and coaxial burner experiments. The velocity Held of intake flow is measured with the intake valve lift variation. It is shown that maximum flow velocity is increased and tumble flow become stronger than inverse tumble flow as valve lift increase.