• Journal of Ocean Engineering and Technology
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• v.31 no.1
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• pp.14-21
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• 2017

The erosion of solid particles in a pipe elbow was numerically investigated. A numerical procedure to estimate the sand erosion rate, as well as the particle motion, in the pipe elbow flow was introduced. This procedure was performed based on the combined empirical erosion model and computational fluid dynamics (CFD) analysis to consider the interaction between the particle motion and the eroded surface. The underlying turbulent flow on an Eulerian frame is described by the Reynolds averaged Navier-Stokes (RANS) equations with a $k-{\epsilon}$ turbulent model. The one-way coupled Eulerian-Lagrangian motion of the air flow and sand particles is employed to simulate the particle trajectories and particle-wall interactions on the pipe surfaces. The predicted CFD erosion magnitudes are compared with experimental data from pipe elbows. The erosion rate results do not reveal a good accordance between the simulation and experimental results. It seems that the CFD shows a slightly over-predicted erosion ratio.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.19 no.6
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• pp.63-76
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• 2016

Slope revegetation refers to the use of vegetation and construction to protect a barren slope devastated by road and building construction. Among many revegetation strategies, hydroseeding has been widely utilized to stabilize barren slopes and has become the representative approach. Previous studies on slope stability have been conducted from a civil engineering perspective, mainly evaluating the stability of cut-slopes on solid bedrock and the use of concrete structures to stabilize devastated slopes. This study was conducted to develop a method to evaluate erosion risk of revegetated cut-slopes, based on criteria derived from previous studies. Twenty-five factors were surveyed on both on-the-spot erosion slopes and non-erosion slopes after slope revegetation to compare slope types. The scores of all non-erosion slopes exceed 80 score while erosion slopes are 80 below. Erosion slopes got the range of 68-74 score while non-erosion slopes got the range of 81-100 score in the first result which was not applied for weighted-values. The scores of all non-erosion slopes exceeded 3.10, while erosion slopes were below 3.10. Erosion slopes were in the range of 2.73-3.09, while non-erosion slopes were in the range of 3.15-3.90 in the second result, which was applied with weighted-values according to the AHP result from a previous study.

• Journal of computational fluids engineering
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• v.18 no.3
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• pp.94-101
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• 2013

In the present study, a practical method to predict cavitation erosion, which caused a critical damage on hydraulic machineries, was developed. Impact and critical velocities were defined to develop a practical method for the prediction of cavitation erosion. To develope the practical method, the computational fluid dynamics (CFD) was introduced. Cavitating flows with erosion in a converging-diverging nozzle and around a hydrofoil were simulated by developed and validated code. Based on the CFD results, the cavitation erosion coefficient was derived by a curve fitting method. The cavitation erosion coefficient was formulated as the function of the cavitation and Reynolds numbers. A cavitating flow in an axisymmetric nozzle followed by radial divergence was simulated to validate the developed practical method. For the application to a propeller, a cavitating flow around a propeller was simulated. Predicted damage extent showed similar with damaged full-scale propeller blade.

• Journal of Ocean Engineering and Technology
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• v.34 no.6
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• pp.436-441
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• 2020

Wave field changes resulting from artificial coastal structures constructed in coastal zones have emerged as a major cause of beach erosion, among other factors. The rates of erosion along the eastern coast of Korea have varied mainly owing to the construction of various ports and coastal structures; however, impact assessments of these structures on beach erosion have not been appropriately conducted. Thus, in this study, a methodology to assess the impact of erosion owing to the construction of artificial structures has been proposed, for which a parabolic bay shape equation is used in determining the shoreline angle deformation caused by the structures. Assuming that the conditions of sediment or waves have similar values in most coastal areas, a primary variable impacting coastal sediment transport is the deformation of an equilibrium shoreline relative to the existing beach. Therefore, the angle rotation deforming the equilibrium of a shoreline can be the criterion for evaluating beach erosion incurred through the construction of artificial structures. The evaluation criteria are classified into three levels: safety, caution, and danger. If the angle rotation of the equilibrium shoreline is 0.1° or less, the beach distance was considered to be safe in the present study; however, if this angle is 0.35° or higher, the beach distance is considered to be in a state of danger. Furthermore, in this study, the distance affected by beach erosion is calculated in areas of the eastern coast where artificial structures, mainly including ports and power plants, were constructed; thereafter, an impact assessment of the beach erosion around these areas was conducted. Using a proposed methodology, Gungchon Port was evaluated with caution, whereas Donghae Port, Sokcho Port, and Samcheok LNG were evaluated as being in a state of danger.

• Steel and Composite Structures
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• v.1 no.1
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• pp.75-96
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• 2001

Actual buckling curves are always characterised by the erosion of ideal buckling curves. In case of compact sections this erosion is due to the imperfections, while for thin-walled members, a supplementary erosion is induced by the phenomenon of coupled instabilities. The ECBL approach- Erosion of Critical Bifurcation Load - represents a practical and convenient tool to characterise the instability behaviour of thin-walled members. The present state-of-art paper describes the theoretical background of this method and the applications to cold-formed steel sections in compression and bending. Special attention is paid to the evaluation methods of erosion coefficient and to their validation. The ECBL approach can be also used to the plastic-elastic interactive buckling of thin-walled members, and the paper provides significant results on this line.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.201-205
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• 2015

This paper describes thermal flow characteristic in various pipelines: straight pipeline and curved pipeline. In the Arctic and ocean area, pipelines are exposed to a extremely low temperature ($0{\sim}-40^{\circ}C$). In this situation, three-dimensional flow analysis should be analyzed to investigate thermal effects such as pressure drop, temperature change, velocity deficit and distribution change of liquid droplet of internal fluid. Also, due to freezing of water droplet, impingement erosion is expected in the curved pipeline. The stability of the pipelines can be influenced by impingement erosion. In this paper, multi-phase and multi-species analysis was introduced to analyze the flow characteristics and impingement erosion of Arctic and ocean pipelines.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2669-2681
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• 2021

Valve is widely used in the various industry areas to adjust and control the flow. Cavitation frequently takes place and sometimes is inevitable in various types of valve to cause the erosion damage. Therefore, how to control and minimize the effect of cavitation is still an important topic. This study numerically investigates the cavitating flow in a control valve with a perforated cage. The effects of some parameters on the cavitation are discussed. It also discusses to use the throttling steps to govern the cavitating flow. The results show that the opening degree of valve and the length of downstream divergent connection both influence the cavitation. The increase of the divergent length reinforces the cavitation. And the larger the opening of valve is, the intenser the cavitation is and the more vapor is present. The more throttling steps are helpful to decrease the cavitation.

• Korean Journal of Environment and Ecology
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• v.27 no.5
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• pp.614-624
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• 2013

The purpose of this study is to offer the raw data for establishing the plan of disaster prevention and the continuous conservation of soil ecosystem by grasping the potential soil loss and the danger of erosion using RUSLE method on whole districts in Gyeongju National Park, Korea. In the results of the average amount of soil erosion for the year, the average of all districts was 5.7 ton/ha in annual, and Namsan district was the highest in 7.6 ton/ha in annual and Seoak district was the lowest in 2.1 ton/ha in annual. The dangerous district due to the soil erosion was analyzed as under 1%, and Gumisan and Hwarange district was not serious. But Namsan district was higher than others, especially, there was intensive in all over Geumohbong. Therefore, to protect the all over Geumohbong, we will establish the valid of restoration and management. The types of land cover in Gyeongju National Park mostly showed forest, and as the average amount of soil erosion in forest was 3.7 ton/ha in annual, there was good condition. In the results of the amount of soil erosion due to landform, the deep canyon showed as 7.3 ton/ha in annual per unit area, secondly, the U-shaped valley was analyzed as 6.1 ton/ha in annual. The plain and high ridge were predicted that there occurred the small amount of soil erosion. In future, if we will analyze the amount of soil erosion in Korean National Parks, we will offer the help to establishing the plan of conservation and restoration on soil ecosystem in whole National Parks.

• Journal of Ocean Engineering and Technology
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• v.33 no.6
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• pp.526-534
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• 2019

The average coastline and the erosion control line introduced as the management coastline, and the average shoreline (MSL) was established from the observed coastline. Also, the median grain size and the wave height of 30-years return period were applied. The erosion control line (ECL) was established through the model, HaeSaBeeN. These two lines set the coastline for evaluation. Based on the observed monitoring data along the coastline, the 1-day variation according to the normal distribution was used to estimate the regional variation, and the width of the erosion was calculated by applying the median grain size (D₅₀) and the wave height of 30-years return period through the high-wave coastal erosion width model, i.e., HaeSaBeeN.

• Journal of Environmental Impact Assessment
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• v.20 no.3
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• pp.313-324
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• 2011

The purpose of this study is to present the raw data for establishing the plan of top soil conservation in soil environment and preventing the soil loss by establishing the potential amount of soil loss using RUSLE. The results are as follows. To apply the RUSLE model, we calculated the potential amount of soil loss by using 5 factors; rainfall erosion factor(R), topographical factor(LS), soil erosion factor(K), land cover factor(C) and erosion control factor(P). The assessment map of soil loss was drawn up by classifying 5 grades. According to the soil loss estimation by the RUSLE, it showed that approximately 83.9% of the study area had relatively lower possibility of soil loss which was the 1 ton/ha in annual soil loss. Whereas, the 7.0% of the study area was defined as high risk area which was the 10 ton/ha in annual. Therefore, this area was needed that there was environment-friendly construction of farm land, improvement of cultivation environment and so forth. In future, if we will analyze the amount of soil loss of Gyeongju national park and Hyeongsan river watershed, we will offer the help to establishing the conservation plan of soil environment in Gyeongsangbuk-do.