• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.983-987
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• 2008

Computational simulation has been performed to design optimally the filtration system for IGCC pilot plant. It was analyzed how the different inflow pattern influences the flow field and the particle behavior in a filter vessel. The particle loading onto the filter surface lowers significantly and decreases dramatically with particle size when the dusty gas flows into the filter vessel with a shroud tube through a tangential inlet setup tangentially on the vessel outer wall. However, the particle loading is considerably high when the dusty gas enters the filter vessel through a normal inlet setup vertically on the vessel top wall, and the decrease of the particle loading with particle size is not steeper compared with the tangential inflow pattern.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2587-2593
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• 2014

Ceramic Injection Molding (CIM) is one of wide used processes in industry field and the applications are gradually being expanded to parts of medical and electric devices. In this study, the CIM process were analyzed with FEM and process parameters were studied and analyzed the effect on product quality. The shape of simple flat plate was compared to the shapes with the hole, with the round corner portion or with the side wall portion. If there are holes then the hole around the uneven density distribution and the defects such as weld lines could be occurred. The Large radius of the corners of the product give good formability and fluidity. Not only the shape parameters of product but also the process parameters during CIM are studied. The simulation results showed that the process parameters of temperature, initial fractions and velocity are important design parameters to improve the quality of products.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.292-292
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• 2016

논의 배수특성 분석은 물꼬 크기 및 개소수, 배수로 구성, 규모, 경사, 재질 등과 같은 물리적 특성 인자들의 영향으로 인해 일반적인 유역의 홍수량 산정을 위해 사용되는 수문학적 홍수추적 방법의 적용이 어렵다. 따라서 논에서의 유출을 모의하기 위해서는 수리학적 홍수추적 방법의 적용이 필요하며, 기존의 연구들은 대부분 1차원과 2차원의 수치 해석 기법으로 논의 유출 특성을 분석해왔다. 3차원 수치 해석 기법을 적용할 경우 1차원과 2차원에서 볼 수 없는 유동 특성 등을 파악할 수 있으며, 보다 정확한 유출 모의가 가능할 것으로 기대된다. 하지만 3차원 해석은 비교적 구조가 단순한 논에 적용하기에는 시간과 비용이 과도하게 소모된다는 단점이 있다. 한편, 상사법칙은 주로 실험의 스케일을 줄이기 위해 적용되어 왔다. 정확성에 대한 검증이 이루어진다면, 시간이 오래 걸리는 3차원 모델링에 상사법칙을 적용할 경우, 모의 시간을 단축시킬 수 있는 장점이 있을 것으로 사료된다. 따라서 본 연구에서는 3차원 수치 해석 모형인 FLOW-3D를 이용하여 논에서의 유출을 모의하고, 적용성을 평가하고자 한다. 또한 상사법칙을 이용하여 모의 시간을 단축할 수 있는 방법을 제시하고자 한다. 모의 대상으로 40m x 100m의 논 포장을 구성하였으며, 강우 및 관개에 따른 유출을 모의하였다. 모의 결과는 실측치 및 기존 연구의 결과와 비교하여 적용성을 평가하였다. 또한 수리학적 상사법칙을 적용하여 조건을 변화시켜가며 유출을 모의하였고, 모의 조건 및 모의 시간 변화에 따른 정확성을 분석하였다. 본 연구에서 제시한 방법은 논에서의 유출 모의의 정확성을 향상 시켜, 홍수 발생 시 농경지의 침수 대책 마련에 기여할 수 있을 것으로 기대된다.

• Ecology and Resilient Infrastructure
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• v.8 no.4
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• pp.245-252
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• 2021

A turbidity current in a river and a lake occurs due to diverse nutrient loading including suspended sediment in sediment runoff, which affects water withdrawal and river environments. We developed one dimensional time-variant numerical model based on Python for the Nagdonggang mainstream. We examined the numerical stability and the applicability of the model by performing the simulation of quasi-steady flow in non-flooding for three cases, which are different according to the point and the amount of turbidity inflows in the Nagdonggang upstream and a tributary. The result was reasonable in the respect of the conservation of matter. The model will facilitate to simulate a large river if we can secure the data of turbidity variations in a target river reach or measured points in a field.

• Journal of Korean Society on Water Environment
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• v.27 no.5
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• pp.699-709
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• 2011

The uses of multi-dimensional hydrodynamic and water quality models are increasing to support a sustainable management of large dam reservoirs in Korea. Any modeling study requires selection of a proper spatial dimension of the model based on the characteristics of spatial variability of concerned simulation variables. For example, a laterally averaged two-dimensional (2D) model, which has been widely used in many large dam reservoirs in Korea, assumes that the lateral variations of hydrodynamic and water quality variables are negligible. However, there has been limited studies to give a justification of the assumption. The objectives of this study were to present the characteristics of spatial variations of water quality variables through intensive field monitoring in Daechung Reservoir, and provide information on a proper spatial dimension for different water quality parameters. The monitoring results showed that the lateral variations of water temperature are marginal, but those of DO, pH, and conductivity could be significant depending on the hydrological conditions and local algal biomass. In particular, the phytoplankton (Chl-a) and nutrient concentrations showed a significant lateral variation at R2 (Daejeongri) during low flow periods in 2008 possibly because of slow lateral mixing of tributary inflow from So-oak Stream and wind driven patchiness.

• Archives of Plastic Surgery
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• v.49 no.4
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• pp.531-537
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• 2022

Wide-awake, local anesthesia, no tourniquet (WALANT) is a technique that removes the requirement for operations to be performed with a tourniquet, general/regional anesthesia, sedation or an anesthetist. We reviewed the WALANT literature with respect to the diverse indications and impact of WALANT to discuss the importance of future surgical curriculum integration. With appropriate patient selection, WALANT may be used effectively in upper and lower limb surgery; it is also a useful option for patients who are unsuitable for general/regional anesthesia. There is a growing body of evidence supporting the use of WALANT in more complex operations in both upper and lower limb surgery. WALANT is a safe, effective, and simple technique associated with equivalent or superior patient pain scores among other numerous clinical and cost benefits. Cost benefits derive from reduced requirements for theater/anesthetic personnel, space, equipment, time, and inpatient stay. The lack of a requirement for general anesthesia reduces aerosol generating procedures, for example, intubation/high-flow oxygen, hence patients and staff also benefit from the reduced potential for infection transmission. WALANT provides a relatively, but not entirely, bloodless surgical field. Training requirements include the surgical indications, volume calculations, infiltration technique, appropriate perioperative patient/team member communication, and specifics of each operation that need to be considered, for example, checking of active tendon glide versus venting of flexor tendon pulleys. WALANT offers significant clinical, economic, and operative safety advantages when compared with general/regional anesthesia. Key challenges include careful patient selection and the comprehensive training of future surgeons to perform the technique safely.

• Tunnel and Underground Space
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• v.32 no.3
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• pp.219-230
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• 2022

The Geo-Reservoir Experimental Analogue Technology (GREAT) cell was designed to recreate the thermal-hydro-mechanical conditions of deep subsurface in the laboratory. This apparatus can generate a polyaxial stress field using lateral loading elements, which rotate around the longitudinal axis of a sample and is capable of performing a fluid flow test for samples containing fractures. In the present study, numerical simulations were carried out for triaxial compression tests using the GREAT cell and the mechanical behavior of samples under different conditions of lateral loading was investigated. We simulated an actual case, in which triaxial compression tests were conducted for a polymer sample without fractures, and compared the results between the numerical analysis and experiment. The surface strain (circumferential strain) of the sample was analyzed for equal and non-equal horizontal confining pressures. The results of the comparison showed a good consistency. Additionally, for synthetic cases with a fracture, we investigated the effect of the friction and type of fracture surface on the deformation behavior.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.3
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• pp.158-166
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• 2021

In this paper, a numerical analysis technique using a body force model is investigated to estimate the available net thrust of multi-pod-driven ice-breaking vessels under bollard pull and overload conditions. To employ the body force model in present flow simulations, drag and thrust components acting on the pod unit are calculated by using Propeller Open Water (POW) test data. The available net thrusts according to the direction of operation are evaluated in both bollard pull and overload conditions under deep water. The simulation results are compared with the model test data. The available net thrusts, calculated by the present analysis for ahead operating modes at 3~6 knots which are typical speeds of the target vessel in arctic field, are agreed well with the model test results. It is also found that the present result for astern operating mode appears approximately 6 % larger than the model test result. In addition, the available net thrusts are calculated under the both operating conditions accompanied by shallow water effects, and the main cause of the difference is studied. Based on the result of the present study, it is confirmed that the body force model can be applied to the performance evaluation of multi-pod propulsion system and the main engine selection in early design stage of the vessel.

• Plant Journal
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• v.18 no.2
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• pp.41-45
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• 2022

The conventional communication method using mud flow pressure waves has a speed of 1-2 bps, so it takes a long time to communicate, making real-time control impossible. Although the sound wave communication method for improving the communication speed by 10 times or more has been commercialized, its use is limited due to its high price and there are not many application cases. In this study, the simulator corresponding to the facility was developed to develop performance similar to the actual test results. For simulating sound wave communication through a drill pipe, we proposed a governing equation that can simulate friction damping by mud and developed a numerical analysis model. The attenuation factor was corrected by comparing it with the attenuation rate of sound wave energy at the drilling site. The developed numerical analysis model was applied to the QPSK modulation type communication algorithm to confirm the excellent performance of the communication error rate of 0.04% in the ground. This is the communication performance under the condition that noise has not been mixed yet, and in order to apply it, the technology of reproducing the actual noise signal for mixing by securing the field noise data was established.

• Journal of Ocean Engineering and Technology
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• v.36 no.5
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• pp.326-339
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• 2022

Recently, not only Korea but also the world has been suffering from problems related to coastal erosion. The hard defense method has been primarily used as a countermeasure against erosion. However, this method is expensive and has environmental implications. Hence, interest in other alternative methods, such as the eco-friendly vegetation method, is increasing. In this study, we aim to analyze the hydraulic characteristic of submerged rigid vegetation according to the cross-sectional change through a hydraulic experiment and numerical simulation. From the hydraulic experiment, the reflection coefficient, transmission coefficient, and energy dissipation coefficient were analyzed according to the density, width, and multi-row arrangement of the vegetation zone. From numerical simulations, the flow field, vorticity distribution, turbulence distribution, and wave distribution around the vegetation zone were analyzed according to the crest depth, width, density, and multi-row arrangement distance of the vegetation zone. The hydraulic experiment results suggest that the transmission coefficient decreased as the density and width of the vegetation zone increased, and the multi-row arrangement condition did not affect the hydraulic characteristics significantly. Moreover, the numerical simulations showed that as the crest depth decreased, the width and density of vegetation increased along with vorticity and turbulence intensity, resulting in increased wave height attenuation performance. Additionally, there was no significant difference in vorticity, turbulence intensity, and wave height attenuation performance based on the multi-row arrangement distance. Overall, in the case of submerged rigid vegetation, the wave energy attenuation performance increased as the density and width of the vegetation zone increased and crest depth decreased. However, the multi-row arrangement condition did not affect the wave energy attenuation performance significantly.