• Journal of Biomedical Engineering Research
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• v.25 no.6
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• pp.489-496
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• 2004

Insertion of cannulae into vessels may disturb the blood flow doing non-physiological load and stress on blood cells such that ADP may increase and result in hemolysis. Authors used the computational method to simulate the 3-dimensional blood flow inside of the cannula using numerical method. We limited the research to within the drainage cannulae with side holes inserted through the human vein. In this paper, 9 different cannulae with side holes categorized by the number of side holes of 4, 12, and 20, and also categorized by the array type of side holes of staggered array, in-line array, and alternative in-line array were studied and compared to the cannula with no side holes by using CFD analysis. We evaluated the flow rate, the wall shear stress, and the shear rate and compared them with one another to estimate the effect of the side holes. The flow rate is not proportional to the number of the side holes. However, larger number of side holes can reduce the mean shear rate. Both the number and the array type of side holes play an important role on the fluid dynamics of the blood flow in cannulae.

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.613-620
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• 2021

A flow channel shape of PEMFC has an influence on the internal flow uniformity. If the reactant distribution in a flow path is not uniform during operation, both catalyst deactivation and mechanical damage of membrane could occur resulting in decreasing the membrane electrode assembly (MEA) durability. Numerous studies concerning flow design have been conducted to make smooth supply and uniform distribution of reactants in fuel cells. The baffle of flow path could improve fuel cell performance through the forced convection effect. A sub-channel, as an additional air flow path, could increase the reactant concentration and reduce the mass transfer loss via a smooth water discharge. In this study, computational fluid dynamics (CFD) was used to analyze the effect of blocks and sub-channels on the current density and oxygen concentration of the fuel cell. As a result, the limit current density and oxygen concentration at a rear block increased when using blocks and sub-channels in a flow channel. In particular, the current density increased significantly when the sub-channel was placed between two blocks. Also, the sub-channel position was optimized by analyzing the oxygen concentration, and the oxygen concentration was recovered at a rear block in the fuel cell.

• Journal of the Korea Society for Simulation
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• v.27 no.4
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• pp.19-26
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• 2018

The aerial launching UAV(Unmanned Aerial Vehicle) mainly uses a set of folding tandem wings to maximize flight performance and minimize the space required for mounting in a mothership. This folding tandem wing has a unique aerodynamic problem that is different from the general type of fixed wing aircraft, such as the rear wing interference problem caused by the wing of the front wing wake and vortex, and the imbalance of the pivot moment applied to the front and rear wings when the wing is deployed. In this paper, we have modeled and simulated various cases through computational fluid dynamics based on the finite volume method and analyzed various aerodynamic phenomena of the tandem wing type aircraft. We find that the front wing shall be installed higher than the rear for minimizing the wake influence and the rear wing can be deployed faster than the front because of the pivot moment due to aerodynamic forces. Also, considering the pivot moment due to aerodynamic force, the rear wing can be deployed much faster than the front wing. Therefore, it is necessary to consider it when developing the wing deploy mechanism.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.5
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• pp.617-626
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• 2019

This study analyzes the optimal location of gas detectors through the gas dispersion in a cargo compressor room of a 174K LNG carrier equipped with high-pressure cargo handling equipment; in addition, we propose a reasonable method for determining the safety regulations specified in the new International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC). To conduct an LNG gas dispersion simulation in the cargo compressor room-equipped with an ME-GI engine-of a 174 K LNG carrier, the geometry of the room as well as the equipment and piping, are designed using the same 3D size at a 1-to-1 scale. Scenarios for a gas leak were examined under high pressure of 305 bar and low pressure of 1 bar. The pinhole sizes for high pressure are 4.5, 5.0, and 5.6mm, and for low pressure are 100 and 140 mm. The results demonstrate that the cargo compressor room will not pose a serious risk with respect to the flammable gas concentration as verified by a ventilation assessment for a 5.6 mm pinhole for a high-pressure leak under gas rupture conditions, and a low-pressure leak of 100 and 140 mm with different pinhole sizes. However, it was confirmed that the actual location of the gas detection sensors in a cargo compressor room, according to the new IGC code, should be moved to other points, and an analysis of the virtual monitor points through a computational fluid dynamics (CFD) simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.310-316
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• 2019

In automotive application, customers are demanding high efficiency and various functions for convenience. The demand for these automotive applications is steadily increasing. In this study, it has been studied the analysis of heat flow to improve the PCB(printed circuit board) heating performance of WPC (wireless power charger) recently developed for convenience. The charging performance of the wireless charger has been reduced due to power dissipation and thermal resistance of PCB. Therefore, it has been proposed optimal PCB design, layout and position of electronic parts through the simulation of heat flow analysis and PCB design was analyzed and decided at each design stage. Then, the experimental test is performed to verify the consistency of the analysis results under actual environmental conditions. In this paper, The PCB modeling and heat flow simulation in transient response were performed using HyperLynx Thermal and FloTHERM. In addition, the measurement was performed using infrared thermal imaging camera and used to verify the analysis results. In the final comparison, the error between analysis and experiment was found to be less than 10 % and the heating performance of PCB was also improved.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.415-421
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• 2021

This study analyzed the effect on the cooling performance of the channel shape of a heat sink for an insulated gate bipolar transistor (IGBT). A serpentine channel was used for this analysis, and the parameter for the analysis was the number of curves. The analysis was conducted using computational fluid dynamics with the commercial software ANSYS fluent. One curve in the channel improved the heat dissipation performance of the heat sink by up to 8% compared to a straight-channel heat sink. However, two curves in the channel could not improve the heat discharge performance further. Instead, the two curves caused a higher pressure drop, which induces parasitic loss for the pumping of coolant. The pressure drop of the two-curve channel case was 2.48-2.55 times larger than that of a one-curve channel. This higher pressure drop decreased the heat discharge efficiency of the heat sink with two curves. The discharge heat per unit pressure drop was calculated, and the result of the straight heat sink was highest among the analyzed cases. This means that the heat discharge efficiency of the straight heat sink is the highest.

• Korean Journal of Construction Engineering and Management
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• v.22 no.4
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• pp.3-10
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• 2021

According to the IPCC, humans are influencing the climate system. Such changes in the climate system can cause problems in the supply of food ingredients in the agricultural field by changing the existing growing environment. To solve this problem, vertical farms can be a good alternative for a stable supply of food ingredients. Although the vertical smart farm pays close attention to maintaining and managing the growing environment of crops, it is difficult to uniformly implement temperature, humidity, illumination, oxygen, and carbon dioxide concentrations in the building space. As a result of conducting computational fluid dynamics analysis to ensure air uniformity, a remarkable result is that it is advantageous to continuously spray suitable carbon dioxide CO2 concentrations for a long period of time for air uniformity in a vertical smart farm. Through this result, it is possible to efficiently plan a growing environment system optimized for a vertical smart farm. Based on this study, if efficient crops are produced by creating an optimized growing environment for vertical smart farms, it will be able to contribute to the development of the agricultural field.

• Composites Research
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• v.35 no.6
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• pp.447-455
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• 2022

Currently, the problem of pollution of the marine environment by microplastics is emerging seriously internationally. In this study, to develop a lightweight portable microplastic collection device, the types and number of microplastics in 21 coastal areas nationwide in Korea were investigated. And CFRP (Carbon Fiber Reinforced Plastic), GFRP (Glass Fiber Reinforced Plastic), ABS (Acrylonitrile Butadiene Styrene copolymer) and aluminum were applied for design and analysis of microplastic collection device to have the durability, corrosion resistance and lightweight. As a result of sample collection and classification from the shore, it was confirmed that microplastics were distributed the most in Hamdeok beach, and the polystyrene was found to be mainly distributed microplastics. Particle information through coastal field survey and CFD (Computational Fluid Dynamics) analysis were used to analyze the flow rate and distribution of particles such as sand and impurities, which were applied to the structural analysis of the cyclone device using the finite element method. As a result of structural analysis considering the particle impact inside the cyclone device, the structural safety was examined as remarkable in the order of CFRP, GFRP, aluminum, and ABS. In the view of weight reduction, CFRP could be reduced in weight by 53%, GFRP by 47%, and ABS by 61% compared to aluminum for the cyclone device.

• Advances in aircraft and spacecraft science
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• v.9 no.5
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• pp.415-431
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• 2022

Secondary flows have a huge impact on losses generation in modern low pressure gas turbines (LPTs). At design point, the interaction of the blade profile with the end-wall boundary layer is responsible for up to 40% of total losses. Therefore, predicting accurately the end-wall flow field in a LPT is extremely important in the industrial design phase. Since the inlet boundary layer profile is one of the factors which most affects the evolution of secondary flows, the first main objective of the present work is to investigate the impact of two different inlet conditions on the end-wall flow field of the T106A, a well known LPT cascade. The first condition, labeled in the paper as C1, is represented by uniform conditions at the inlet plane and the second, C2, by a flow characterized by a defined inlet boundary layer profile. The code used for the simulations is based on the Discontinuous Galerkin (DG) formulation and solves the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the Spalart Allmaras turbulence model. Secondly, this work aims at estimating the influence of viscosity and turbulence on the T106A end-wall flow field. In order to do so, RANS results are compared with those obtained from an inviscid simulation with a prescribed inlet total pressure profile, which mimics a boundary layer. A comparison between C1 and C2 results highlights an influence of secondary flows on the flow field up to a significant distance from the end-wall. In particular, the C2 end-wall flow field appears to be characterized by greater over turning and under turning angles and higher total pressure losses. Furthermore, the C2 simulated flow field shows good agreement with experimental and numerical data available in literature. The C2 and inviscid Euler computed flow fields, although globally comparable, present evident differences. The cascade passage simulated with inviscid flow is mainly dominated by a single large and homogeneous vortex structure, less stretched in the spanwise direction and closer to the end-wall than vortical structures computed by compressible flow simulation. It is reasonable, then, asserting that for the chosen test case a great part of the secondary flows details is strongly dependent on viscous phenomena and turbulence.

• Membrane and Water Treatment
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• v.14 no.3
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• pp.129-140
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• 2023

The appropriate injection of H₂O₂ is essential to produce hydroxyl radicals (OH·) by mixing H₂O₂ quickly and exposing the resulting H₂O₂ solution to UV irradiation. This study focused on evaluating mixing device of H₂O₂ as a design factor of UV/H₂O₂ AOP pilot plant using a surface water. The experimental investigation involved both experimental and model-based analyses to evaluate the mixing effect of different devices available for the H₂O₂ injection of a tubular hollow pipe, elliptical type of inline mixer, and nozzle-type injection mixer. Computational fluid dynamics analysis was employed to model and simulate the mixing devices. The results showed that the elliptical type of inline mixer showed the highest uniformity of 95%, followed by the nozzle mixer with 83%, and the hollow pipe with only 18%, after passing through each mixing device. These results indicated that the elliptical type of inline mixer was the most effective in mixing H₂O₂ in a bulk. Regarding the pressure drops between the inlet and outlet of pipe, the elliptical-type inline mixer exhibited the highest pressure drop of 15.8 kPa, which was unfavorable for operation. On the other hand, the nozzle mixer and hollow pipe showed similar pressure drops of 0.4 kPa and 0.3 kPa, respectively. Experimental study showed that the elliptical type of inline and nozzle-type injection mixers worked well for low concentration (less than 5mg/L) of H₂O₂ injection within 10% of the input value, indicating that both mixers were appropriate for required H₂O₂ concentration and mixing intensity of UV/ H₂O₂ AOP process. Additionally, the elliptical-type inline mixer proved to be more stable than the nozzle-type injection mixer when dealing with highly concentrated pollutants entering the UV/H₂O₂ AOP process. It is recommended to use a suitable mixing device to meet the desired range of H₂O₂ concentration in AOP process.