• Water Engineering Research
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• v.1 no.4
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• pp.259-266
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• 2000

Scour hole is formed due to the high shear stress of the jet flow at the outlet of a hydraulic structure and vortex erosion occurs in the scour hole. It is important to determine the amount of vortex erosion occurs in the scour hole. It is important to determine the amount of vortex erosion for the design of bed protection. If the vortex erosion continues and reaches to the hydraulic structure, it causes the deformation of the structure itself. To obtain the amount of the vortex erosion, it is necessary to determine the shear velocity of the line vortex in the scour hole was derived by the theory of energy conservation and found to be related to the upstream overflow velocity. The amount of vortex erosion from the scour hole was obtained using entrainment equation for given value of shear velocity. For a design purpose, if the flow velocity at the end of an apron and the properties of bed material are given, the amount of vortex erosion was obtained.

• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.141-153
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• 2022

In this study, a numerical model of debris flow considering driftwood and entrainment erosion is developed. Subsequently, numerical simulations based on the observation data of the 2011 Mt. Umyeon are performed. To develop the debris flow model, the Nays2DFlood model, which is a flooding model based on the shallow water equation, is coupled with the transport diffusion of mixed sediment concentration, debris flow bottom shear stress, and entrainment erosion modules. The simulation closely reproduced the depth, flow velocity, and debris flow volume of Mt. Umyeon. In addition, the reproducibility of the simulation result with driftwood is more accurate than that without driftwood. The results of this study can facilitate in establishing measures to reduce debris disasters, thus alleviating the current increase in debris damage due to climate change.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.4
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• pp.82-89
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• 1997

A physically-based soil-water erosion model with simple hydrology and Rose & Hairsine's erosion concept is described, and was implemented in the form of computer program. The model derived from the concept of stream power(Bagnold, 1977) considers settling velocity characteristics of the soil and distinguishes between the processes of entrainment and re-entrainment. It deals separately with rill flow and sheet flow, handles vegetation in terms of soil contact cover, and has the ability to simulate soil movement on nonuniform slopes. The model predicted sediment concentrations reasonably with the results of Mclsaac et al. (1990). It showed a capability to quantitatively predict the movement of soil on uniform and nonuniform slopes. Among the model parameters, soil depositability $({\phi})$ was the most sensitive from the sensitivity analysis.

• Journal of Korea Water Resources Association
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• v.53 no.9
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• pp.637-646
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• 2020

The shallow landslide-trigerred debris flow in hillslope catchments is the primary geological phenomenon that drives landscape changes and therefore imposes risks as a natural hazard. In particular, debris flows occurring in urban areas can result to substantial damages to properties and human injuries during the flow and sediment transport process. To alleviate the damages as a result of these debris flow, analytical models for flow and damage prediction are of significant importance. However, the analysis of debris flow model parameters is not yet sufficient, and the analysis of the entrainment, which has a significant influence on the flow process and the damage extent, is still incomplete. In this study, the effects of erosion and erosion process on the flow and the impact area due to the change in the soil parameters are analyzed using Deb2D model, a flow analysis model of debris developed in Korea. The research is conducted for the case of the Mt. Umyeon landslide in 2011. The resulting impacted area, total debris-flow volume, maximum velocity and inundated depth from the Erosion model are compared to the field survey data. Also, the effect of the entrainment changing parameters is analyzed through the erosion shape and depth. The debris flow simulation for the Raemian and Shindong apartment catchment with the consideration of entrainment effect and erosion has been successful. Each parameter sensitivity could be analyzed through sensitivity analysis for the two basins based on the change in parameters, which indicates the necessity of parameter estimation.

• Water for future
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• v.27 no.1
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• pp.101-109
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• 1994

Characteristics of the vortex structure and the secondary scour at downstream part of the hydraulic structure such as drainage sluice or spillway ere studied. Mean shear velocity in the scour hole could be derived by the theory of energy conservation and the amount of a vortex erosion could be obtained using entrainment equation for given value of a shear velocity. Comparison of erosion rates with others showed a large value at low shear velocity due to the continuous and strong upward flow of the macroturbulence different from the conventional vortex formed in the lee-side of a sand ripple. For a design purpose, if the flow depth at the end of an apron and the properties of bed material are given, the amount of vortex erosion can be known.

• Magazine of the Korean Society of Agricultural Engineers
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• v.22 no.4
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• pp.108-114
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• 1980

A deterministic conceptual erosion model which simulates detachment, entrainment, transport and deposition of eroded soil particles by rainfall impact and flowing water is presented. Both upland and channel phases of sediment yield are incorporated into the erosion model. The algorithms for the soil erosion and sedimentation processes including land and crop management effects are taken from the literature and then solved using a digital computer. The erosion model is used in conjunction with the modified Kentucky Watershed Model which simulates the hydrologic characteristics from watershed data. The two models are linked together by using the appropriate computer code. Calibrations for both the watershed and erosion model parameters are made by comparing the simulated results with actual field measurements in the Four Mile Creek watershed near Traer, Iowa using 1976 and 1977 water year data. Two water years, 1970 and 1978 are used as test years for model verification. There is good agreement between the mean daily simulated and recorded streamflow and between the simulated and recorded suspended sediment load except few partial differences. The following conclusions were drawn from the results after testing the watershed and erosion model. 1. The watershed and erosion model is a deterministic lumped parameter model, and is capable of simulating the daily mean streamflow and suspended sediment load within a 20 percent error, when the correct watershed and erosion parameters are supplied. 2. It is found that soil erosion is sensitive to errors in simulation of occurrence and intensity of precipitation and of overland flow. Therefore, representative precipitation data and a watershed model which provides an accurate simulation of soil moisture and resulting overland flow are essential for the accurate simulation of soil erosion and subsequent sediment transport prediction. 3. Erroneous prediction of snowmelt in terms of time and magnitute in conjunction with The frozen ground could be the reason for the poor simulation of streamflow as well as sediment yield in the snowmelt period. More elaborate and accurate snowmelt submodels will greatly improve accuracy. 4. Poor simulation results can be attributed to deficiencies in erosion model and to errors in the observed data such as the recorded daily streamflow and the sediment concentration. 5. Crop management and tillage operations are two major factors that have a great effect on soil erosion simulation. The erosion model attempts to evaluate the impact of crop management and tillage effects on sediment production. These effects on sediment yield appear to be somewhat equivalent to the effect of overland flow. 6. Application and testing of the watershed and erosion model on watersheds in a variety of regions with different soils and meteorological characteristics may be recommended to verify its general applicability and to detact the deficiencies of the model. Futhermore, by further modification and expansion with additional data, the watershed and erosion model developed through this study can be used as a planning tool for watershed management and for solving agricultural non-point pollution problems.

• Journal of the Korean Geotechnical Society
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• v.32 no.10
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• pp.17-29
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• 2016

A debris flow analysis model has been developed to simulate the erosion and entrainment of soil layer. Special attention is given to the model which represents strength softening behaviour of soil layer due to velocity of deformation. The 3D FE analysis by Coupled Eulerian-Lagrangian (CEL) model is conducted to simulate the debris flow. The model is validated using published data on laboratory experiment (Mangeny et al., 2010). It has been definitely shown that proposed model is in good agreement with the results of laboratory data. Futhermore, the FE analysis is conducted to ensure capability of simulating the real scale debris flow. The result of Ramian watershed, Korea shows that the debris flow has increased the volume and speed and it is in good agreement with field investigation. Based on this, it is confirmed that proposed model shows good agreement of the behavior of the actual and analytical debris flow.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.2
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• pp.155-160
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• 2004

Water jet trajectories and velocity deficits from a high pressurize nozzles were experimentally observed. In this article, several parameters affecting plugging and erosion onto the steam generator tube were quantitatively analyzed. Visualization, velocity distribution, and spray growth rate with different nozzle configurations have been mainly focused using a 2-D PDPA (Phase Doppler Particle Analyzer) system. The results indicated that trajectories along the centerline regardless of their momentum has its potential core region. However, the phenomena from the peripheral part need to be meticulosly considered. Accordingly, it is evident that quantitative velocity deficits at the outer region are outstanding due to the aerodynamical drag and entrainment.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.3
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• pp.37-43
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• 2004

Water-jet trajectory visualization and velocity deficits from a high pressurized steam-generator nozzles were experimentally observed. In order to find an optimal nozzle configuration. several parameters affecting plugging and erosion onto the steam generator tube were quantitatively analyzed. For the experiments, a high-pressurized pump (pressure in use: 200 kg/$\textrm{cm}^2$, 15 HP, 11 kW, output flow Q : 301/min) was utilized. Visualization, velocity distribution, and spray growth rate with different nozzle configurations have been mainly focused using a 2-D PDPA system. The results indicated that trajectories along the centerline regardless of their configurations has its potential core region. However, the phenomena from the peripheral part need to be meticulously considered. Accordingly, it is evident that quantitative velocity deficits at the outer region are outstanding due to the aerodynamical drag and entrainment.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.138-138
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• 2023

본 연구에서는 유목과 연행침식을 고려한 토석류 수치모형을 개발하여 2011년 발생한 우면산 산사태의 관측데이터를 기반으로 수치모의를 수행하였다. 토석류 모형개발을 위해 천수방정식 기반의 침수모형인 Nays2DFlood 모형에 혼합유사농도의 이송확산, 토석류 지면전단응력, 연행침식모듈을 추가하였으며 유목생성과 유목거동 모의를 위해 입자법 기반의 유목동력학 모형을 결합하였다. 개발된 모형을 검증하기 위해, 민감도분석을 수행하였으며, 모의결과, 우면산 산사태 당시 래미안 APT에 피해를 끼친 충격수심과 충격유속, 최종 토석류 체적을 양호하게 재현한 것으로 판단된다. 또한 토석류를 구성하는 토사입경이 작을수록 토사점성에 의한 전단응력의 증가로 토석류 유속과 수심이 감소했지만 연행침식량이 증가하였으며, 토사입경이 증가하면 유속과 수심이 증가하고 연행침식량은 감소한 것으로 나타났다. 또한 본 연구에서 개발된 토석류 거동모형은 토사입경, 침식 및 퇴적계수 등의 다양한 토석류 매개변수가 요구되기 때문에, 이러한 물성치 데이터가 현장 또는 실내실험에서 충분히 확보되어야 모형의 정확도가 향상될 것으로 판단된다. 따라서, 향후 연구에서는 본 연구에서 고찰된 모형의 적용성과 한계점을 고려하여 토석류 거동을 예측모의 한다면 보다 세부적으로 토석류와 유목거동을 예측분석해 볼 수 있을 것으로 사료된다. 또한 본 연구의 결과는 기후변화로 인한 강우발생의 불확실성과 이로 야기되는 토석류 발생을 사전에 예측하여 토석류 저감대응방안을 구축하는 일환으로 활용 될 수 있을 것으로 기대된다.