• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.3
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• pp.451-461
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• 2016

The objective of this study is to illustrate the methods and procedures for estimating the failure probability of small fill dams subjected to earthquake events and to estimate the seismic failure probability of the Korean disaster risk fill dams where geotechnical information is not available. In this study, first of all, seismic failure probabilities of 7 disaster risk small fill dams, where geotechnical information is available, were evaluated using event tree analysis. Also, the methods and procedures for evaluating probabilities are illustrated. The relationship between dam height and freeboard for 84 disaster risk small dams, for which the safety diagnosis reports are available, was examined. This relationship was associated with the failure computation equation contained in the toolbox of US Army corps of engineers. From this association, the dam height-freeborard critical curve, which represents 'zero' failure probability, was derived. The seismic failure probability of the Korean disaster risk fill dams was estimated using the critical curve and the failure probabilities computed for 7 small dams.

• Design & Manufacturing
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• v.16 no.2
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• pp.26-32
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• 2022

It is known that the fluidized bed incinerator, which is the subject of analysis, shows excellent performance in heat and mass transfer due to excellent mixing and contact performance between fluidized sand and fuel, and also shows relatively good combustion characteristics thanks to good mixing and long residence time for low-grade fuels. have. In this study, air flow analysis is performed to understand the characteristics of co-firing of sludge, waste oil and solid waste in the fluidized bed incinerator, flow characteristics of flue gas, and discharge characteristics of pollutants.The fluidized bed incinerator subject to analysis is a facility that incinerates factory waste and general household waste together with sludge, with a processing capacity of 32 tons/day. to be. In addition, the operation method was designed for continuous operation for 24 hours. As a result, it can be seen that the lower combustion air and the introduced secondary air are changed to a strong turbulence and swirl flow form and exit through the outlet while rotating inside the freeboard layer. The homogeneous one-way flow form before reaching the secondary air nozzle has very high diffusivity with the high-speed jet flow of the nozzle.

• Journal of Ocean Engineering and Technology
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• v.29 no.1
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• pp.62-69
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• 2015

Coastlines are protected by breakwater structures against the erosion of sand or other materials along beaches due to wave action. This research examined the use of physical modeling to determine the effects of the tetrapod size and vertical walls of a rubble mound on the volume of wave overtopping under irregular wave conditions in coastal areas in Busan Yacht Harbor. In this analysis model, the structures were studied using irregular waves and the JONSWAP wave energy spectrum. To understand the effects of the tetrapod size and heights of the vertical wall, the study considered vertical walls of 0, 1.78, 6.83, and 9.33 cm with armor double layered material tetrapods of 8, 12, 16, and 20 tons. An extensive number of experiments covering a relatively large range of variables enabled a comprehensive discussion. First, in the presence of a short vertical wall, the water level played a key role in the overtopping discharge. In such circumstances, the values of the wave overtopping discharge decreased with increasing freeboard size. In the presence of a tall freeboard and middle, the value of the wave overtopping discharge was equally influenced by the vertical wall factor. Moreover, the tetrapod size decreased by an increase in the vertical wall factor, and relationship between them resulted in a short wall height. From an engineering point of view, considering a small water level may allow the choice of a shorter vertical wall, which would ultimately provide a more economical design.

• Journal of Korea Water Resources Association
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• v.51 no.4
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• pp.371-381
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• 2018

Domestic agricultural reservoir dam facilities are difficult to manage water resources because of the in summer rainfall increase due to aging and climate change, it is expected that the dam risk will be large due to the overflow. In this study, author selected study basin in order to evaluate hydrological safety of agricultural reservoir dam facilities. And calculated the probable rainfall, Present PMP, Future PMP considering climate change. Also, author carried quantitative analysis out for increasing rainfall due to climate change, analyze freeboard assessment of agricultural reservoir by calculate flood discharge, reservoir flood routing according to rainfall scenarios. As a result of evaluate hydrological safety of agricultural reservoir dam facilities using Future PMP considering climate change, Gosam, Kumkwang, Miho, Cheongcheon reservoir had the Highest Water Level over the design flood level, it is analyzed that it would be vulnerable to overflow risk.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.535-543
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• 2022

A CPFD (Computational particle fluid dynamics) model of solar fluidized bed receiver of silicon carbide (SiC: average d_p=123 ㎛) particles was established, and the model was verified by comparing the simulation and experimental results to analyze the effect of particle behavior on the performance of the receiver. The relationship between the heat-absorbing performance and the particles behavior in the receiver was analyzed by simulating their behavior near bed surface, which is difficult to access experimentally. The CPFD simulation results showed good agreement with the experimental values on the solids holdup and its standard deviation under experimental condition in bed and freeboard regions. The local solid holdups near the bed surface, where particles primarily absorb solar heat energy and transfer it to the inside of the bed, showed a non-uniform distribution with a relatively low value at the center related with the bubble behavior in the bed. The local solid holdup increased the axial and radial non-uniformity in the freeboard region with the gas velocity, which explains well that the increase in the RSD (Relative standard deviation) of pressure drop across the freeboard region is responsible for the loss of solar energy reflected by the entrained particles in the particle receiver. The simulation results of local gas and particle velocities with gas velocity confirmed that the local particle behavior in the fluidized bed are closely related to the bubble behavior characterized by the properties of the Geldart B particles. The temperature difference of the fluidizing gas passing through the receiver per irradiance (∆T/I_DNI) was highly correlated with the RSD of the pressure drop across the bed surface and the freeboard regions. The CPFD simulation results can be used to improve the performance of the particle receiver through local particle behavior analysis.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2015.11a
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• pp.256-258
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• 2015

연안지역에서는 강우의 증가로 인한 재해와 해수면 상승으로 인한 재해 등 두 개 이상의 재해가 복합적으로 발생할 수 있고, 그 피해도 더 크게 발생할 수 있으므로 이를 동시에 고려한 연구가 필요한 실정이다. 본 연구에서는 태화강 유역을 대상으로 기후변화로 인한 강우량의 증가와 해수면 상승이 연안 지역과 인접한 하천에 미치는 영향을 평가하고자 하였다. 수문모형과 수리모형을 구축하였고, 미래 평균 확률강우량 증가율과, 해수면 상승고를 적용하여 기후변화에 따른 홍수량 및 홍수위를 산정하였다. 이를 통해 제방에 대한 여유고를 구하였고, 하천설계기준의 여유고를 만족하는지 검토하였다. 분석 결과, 전체 구간 40.17km중 약57~78.9%의 구간이 여유고를 만족하지 못하였다. 해수면 상승의 영향으로 홍수위의 변화는 하류부의 일정 구간까지만 영향 미쳤고, 해수면 상승을 고려하지 않을 때 여유고가 만족하지 못하는 구간은 약1.9~3.8% 감소하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.911-918
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• 2013

Two - dimensional numerical analysis model(RMA2), is mainly applied to analyze the flood water levels, velocities and change of river bed at the downstream of Dam. The analysis result be able to influence to Gwangchon bridge from Juam dam, freeboard be insufficient 0.7m to left bank 300m section of dam downstream. Bank overflow is appear to all section of Bosung river to PMF spill condition. Inundated district is appear to river confluence to 200year frequency and is expand to bank overflow to PMF spill condition. Velocity in the channel was simulated high velocity to the bridge and narrow reach and appear to riverbed degradation.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.5
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• pp.331-339
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• 2020

In this study, ways to reduce the edge pressure at the bottom plate of the caisson breakwater were considered. The water depth, freeboard, design wave height and period, and the location of the center of gravity on the super-structure of the breakwater were selected as key design variables that influence the edge pressure, and analyzed how the edge pressure changes according to the change of this key variables. The pressure distribution formulae suggested in the design standard was applied for the calculation of design wave forces. Based on the wave forces, the required effective self-weight of the super-structure and the minimum width of the caisson were determined to have a safety factor of 1.2 against sliding and overturning. From the results, it was found that the edge pressure rapidly increased as the water depth increased, and could exceed the allowable bearing capacity when it reached a certain water depth which is 20 m within the analysis conditions. It was also confirmed that the edge pressure gradually increased linearly as the freeboard increased, but decreased with the increase of the wave height and period. This edge pressure could be significantly reduced up to more than 20% by moving the center of gravity of the super-structure to the seaside, which is 5% of the caisson width. Based on the analysis results and the recently conducted research results, a method was proposed to reduce the edge pressure that can be used in the design.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1835-1839
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• 2006

최근 빈번히 발생하는 국지성 집중호우 등의 기상이변과 도시화로 인한 불투수 면적의 증가는 급격한 유출량의 변화를 가져와 홍수로 인한 피해를 가중시킬 수 있다. 따라서 홍수방어시설인 제방의 경우 발생가능성은 낮지만 확률홍수량에 따른 제방 여유고의 평가도 필요하다. 본 연구에서는 대표적 도시하천인 탄천을 대상으로 하천정비기본계획(2000)에 수립된 계획홍수량과 최근 7년간 실측한 관측 결과로 계산한 확률홍수량을 조건으로 각각의 경우에 따른 한강 합류부(하류단)부터 상류 9 Km까지의 제방 여유고를 국내와 국외의 설계기준으로 비교, 검토하였다. 검토조건으로는 계획홍수량에 대해서는 3가지 경우의 하류단 수위를 경계조건으로 설정하였고 확률홍수량(80년, 100년, 200년 빈도)에 대해서는 각각의 경우에 발생 가능한 하류단 수위를 경계조건으로 설정하였다. 검토결과 탄천의 경우 계획홍수량에 대해서는 대체로 안전측으로 나타났지만 계획빈도 이상의 확률홍수량에 대해서는 국내, 일본의 설계기준에 제시된 여유고보다 상류 일부구간에서 여유고가 부족한 경향을 보이는 것으로 나타났다. 제방 여유고를 미국(도시하천의 경우 최소 0.91 m)의 경우와 비교하여도 안전측에 속한다고 평가할 수 있다. 하지만 본 검토의 대상인 제방이외의 일부 수공구조물(교량등)에서 여유고가 일부 부족한 것도 확인할 수 있었다. 이에 새로이 하천정비를 실시할 탄천(2006년 예정)의 경우 이러한 부분에 대한 검토 및 보완이 필요할 것으로 사료된다.

• Journal of Advanced Research in Ocean Engineering
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• v.2 no.3
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• pp.136-149
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• 2016

Green water impact occurs frequently on offshore platform due to waves with a height greater relative to the freeboard of the structure. This phenomenon exerts a large impact load on the deck. In this paper, offshore platform models with green water protectors of various shapes were fixed to the center of a 3D wave tank to measure the impact pressure acting on the various points on deck and protectors. The impact pressure distribution differed depending on the protector shape, and various patterns of wave creeping up the protector were observed. The protector shape that exerted the lowest pressure impact on the deck will be useful in the deck design of offshore platform, and the model test results will be expected to be used for designers to select the best protector form.