• Journal of Industrial Technology
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• v.28 no.A
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• pp.3-10
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• 2008

This paper is to investigate the characteristics of debris flow landslides in Gangwon Province through literature review, data collection and analyses and site investigation. As results of data analyses about landslides occurred currently in this province, the landslide in the form of debris flow is found to be 55 %. Therefore major loss and costs are caused by discharge of soil and rock fragments from landslide. From results of analyzing the geometrical characteristics of landslide, length of most of landslide is less than 200 m, their width is in the range of 10 - 40 m, most of them are know to be occurred in lower elevation than 400 m. Slope angle is in the range of 25 - 35 degrees. Comparing the period of rainfall intensity with the time of landslide being occurred, occurrence of landslide is quite related to duration of a heavy rainfall. For measures of controlling water flow discharge and debris flow, considering geological and topographical ground conditions, appropriate selection and building check dam, erosion control dam and ring net is very beneficial for reducing the loss and costs caused by the landslide of debris flow.

• Geomechanics and Engineering
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• v.28 no.1
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• pp.77-87
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• 2022

Many geotechnical analyses require the investigation of water flow within partially saturated soil zone to incorporate the effect of climatic conditions. It is widely understood that the hydraulic properties of the partially saturated soil should be included in the transient seepage analyses. However, the characteristics of dual porosity soils with dual-mode water retention curve are normally modelled using single-mode mathematical equation for simplification of the analysis. In reality, the rainwater flow can be affected significantly by the dual-mode hydraulic properties of the soil. This paper presents the variations of safety factor for dual porosity soil slope with dual-mode water retention curve and dual-mode unsaturated permeability. This paper includes the development of the new dual-mode unsaturated permeability to represent the characteristics of soil with the dual-mode water retention curve. The finite element analyses were conducted to examine the role of dual-mode water retention curve and dual-mode unsaturated permeability on the variations of safety factor under rainfall loading. The results indicate that the safety factor variations of dual porosity soil slope modelled using the dual-mode water retention curve and the unsaturated permeability equation are lower than those of dual porosity slope modelled using single-mode water retention curve and unsaturated permeability equations.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.65-70
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• 2002

Cross-Flow Fan(CFF) are widely used lot industrial equipments and household electric appliances. A design method for CFFs, however, has not been well established because of the complexity of the internal flow. Numerical analysis was performed by using STAR-CD. In this study present the internal flow of CFF, which has varies pin number, and their flowrate were compared

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.5
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• pp.53-61
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• 1995

Analyses of subsurface drainage effects of farmland with respect to pipe and envelop material are made by the laboratory experiments using soil box to give basic information for the subsurface drainage system planning and design. Three different diameter PVC perforated pipes and a mesh pipe are used with envelop materials such as sand, rice bran, and crushed stone. Steady state subsurface drainage flow rate increased as envelop material changed from sand to rice bran and crushed stone. This indicates that as the hydraulic conductivity of the envelop material increases, the drainage flow rate increases. On the other hand, for a given envelop material, the mesh pipe which has the largest openning area shows the largest flow rate while small diameter PVC pipes show small flow rates. This tells that as the openning area and pipe diameter increase, the flow rate increases, too. Therefore, selection of pipe and envelop material should be made in accordance with the design drainage flow rate. Unsteady state subsurface drainage flow rate with respect to time differs for different envelop material. In case the sand was used as an envelop material, the small diameter PVC pipes show larger flow rates than the large diameter PVC pipe and mesh pipe. When the rice bran was used, the mesh pipe shows the largest flow rate, while small diameter pipes show smaller flow rates. In case the crushed stone was used as an envelop material, the large diameter PVC pipe and mesh pipe show larger flow rates, while small diameter pipes show a little bit smaller flow rates. However, the variation of flow rates among different pipes is the smallest when the crushed stone is used. The flow rate curve with respect to the pipe changes little for the crushed stone envelop which has a large hydraulic conductivity, while that changes much for the sand and rice bran envelops. However, it is difficult to draw a consistent relationship between the drainage flow rate and pipe for all the envelop materials. Since the subsurface drainage experiments are made only under the restricted laboratory condition in this study, further study including field experiment is required.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.7
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• pp.483-491
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• 2011

When pipe components made of carbon steel in nuclear, fossil, and industry are exposed to flowing fluid, wall thinning caused by FAC(flow accelerated corrosion) can be generated and eventually ruptured at the portion of pressure boundary. A study to identify the locations generating local wall thinning and to disclose turbulence coefficient related to the local wall thinning was performed. Experiment and numerical analyses for tee of down scaled piping components were performed and the results were compared. In particular, flow visualization experiment which was used alkali metallic salt was performed to find actual location of local wall thinning inside tee components. To disclose the relationship between turbulence coefficients and local wall thinning, numerical analyses were performed for tee components. The turbulence coefficients based on the numerical analyses were compared with the local wall thinning based on the measured data. From the comparison of the results, the vertical flow velocity component(Vr) flowing to the wall after separating in the wall due to the geometrical configuration and colliding with the wall directly at an angle of some degree was analogous to the configuration of local wall thinning.

• Journal of the Korea Convergence Society
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• v.11 no.1
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• pp.195-200
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• 2020

In this study, the flow analyses by type of shock absorber orifice were carried out. A shock absorber is indispensable for the ride comfort that is important at the standard of a good car. As the analysis procedure, the actual speed of the shock absorber was set as the flow rate when the cylinder was advanced. And the flow analysis results on models A, B and C of shock absorber models were compared with each other. As the examination on the flow orifice in the vicinity of each model through the analysis of flow, the performance of shock absorber were recognized. On the whole, model A had the fastest flow rate and also had the largest flow rate. Model B had the slowest flow rate and the flow rate features of models B and C with the same number of orifices were similar. Through this study, it is possible to see which shock absorber orifice model facilitates the flow inside the cylinder and increases the ride comfort. It is seen that this analysis result on the flow analyses by type of shock absorber orifice can be applied by converging with the field of design.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.4
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• pp.537-549
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• 1996

A numerical study of heat and mass transfer has been carried out for a frost formation process on a circular cylinder in a cross flow including the effect of buoyancy. Studies include cases of low and high Reynolds number flows. The effect of normal velocity at the surface which is produced due to mass transfer was included in the analysis as well as heat transfer contribution generated due to mass transfer. Variations of heat transfer and frost growth both in time and in the circumferential direction have been obtained for various buoyancy parameters. The effect of flow directions(identical or opposite directions to the gravity) has been studied to yield different frost growth. Our results have been compared with existing experimental data and are in good agreement. Buoyancy analyses for a high Reynolds number flow agree with full numerical solutions for the case of having the same flow direction as gravity. However, for the opposite direction case, the boundary layer analyses would not be applicable to predict frost growth except the region near the stagnation point.

• International Journal of Highway Engineering
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• v.16 no.2
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• pp.43-52
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• 2014

PURPOSES : To solve problems in current compaction control DCPT(Dynamic Cone Penetrometer Test), highly correlated with various testing methods, simple, and economic is being applied. However, it、s hard to utilize DCPT results due to the few numerical analyses for DCPT have been performed and the lack of data accumulation. Therefore, this study tried to verify the validation of numerical modeling for DCPT by comparing and analyzing the results of numerical analyses with field tests. METHODS: The ground elastic modulus and PR(Penetration Rate) value were estimated by using PFC(Particle Flow Code) 3D program based on the discrete element method. Those values were compared and analyzed with the result of field tests. Also, back analysis was conducted to describe ground elastic modulus of field tests. RESULTS : Relative errors of PR value between the numerical analyses and field tests were calculated to be comparatively low. Also, the relationship between elastic modulus and PR value turned out to be similar. CONCLUSIONS : Numerical modeling of DCPT is considered to be suitable for describing field tests by carrying out numerical analysis using PFC 3D program.

• Geomechanics and Engineering
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• v.9 no.4
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• pp.513-530
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• 2015

Commonly, the base stability of sheeted excavation pits against seepage failure by heave is evaluated by using two-dimensional groundwater flow models and Terzaghi's failure criterion. The objective of the present study is to investigate the effect of three-dimensional groundwater flow on the heave for sheeted excavation pits with various dimensions. For this purpose, the steady-state groundwater flow analyses are performed by using the finite element program ABAQUS 6.12. It has been shown that, in homogeneous soils depending on the ratio of half of excavation width to embedment depth b/D, the ratio of safety factor obtained from 3D analyses to that obtained from 2D analyses $FS_{(3D)}/FS_{(2D)}$ can reach up to 1.56 and 1.34 for square and circular shaped excavations, respectively. As failure body, both an infinitesimal soil column adjacent to the wall (Baumgart & Davidenkoff's criterion) and a three-dimensional failure body with the width suggested by Terzaghi for two-dimensional cases are used. It has been shown that the ratio of $FS_{(Terzaghi)}/FS_{(Davidenkoff)}$ varies between 0.75 and 0.94 depending on the ratio of b/D. Additionally, the effects of model size, the shape of excavation pit and anisotropic permeability on the heave are studied. Finally, the problem is investigated for excavation pits in stratified soils, and important points are emphasized.

• Journal of Environmental Science International
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• v.2 no.3
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• pp.161-177
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• 1993

The Yellow Sand Events observed over the Korean peninsula during 22-24 April, 1993 were examined using the synoptic data and GMS visible image to identify the transport path of the Yellow Sand and the main factor governing the duration of the Yellow Sand phenomenon. The 850 hPa convergence chart and the 700 hPa trajectory analyses of the air mass laden with Yellow Sand particles suggested that the Yellow Sand particles observed over Korea were probably transported from the Gobi Desert and the Loess Plateau. The duration of the Yellow Sand Events was about 35-40 hours rather shorter than normal as the high pressure system centered near the Mongolia region moved rapidly toward the Yellow Sea, which drove away the Yellow Sand particles over the Korean peninsula toward the Japan Islands, furthermore the low-level stratification of the air mass over the Korean penishula showed the unstable atmospheric condition leading to atmospheric diffusion of the particles. The trajectory analyses and the GMS visible image indicated that the long-range transport of the air mass laden with the Yellow Sand particles of this case was more dependent on the 700 hPa air flow than on the 850 hPa air flow.