• 한국안전학회지
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• 제33권3호
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• pp.1-7
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• 2018

Recently, various engineering approaches have been widely used in the accident investigation field to identify the cause of the accident and to predict damage by accident. Computational analysis is the most commonly used method of accident investigation technique. This technique is mainly used to identify the mechanism of the accident generation and to determine the cause when it is difficult to reproduce the situation at the time of the accident or when it is impossible to perform a reproduction experiment. In this study, The gas explosion analysis for LPG explosion accident generated by defect of the blocking action was performed to determine the accident object, gas leakage amount and predicted the damage caused by the accident using 3D laser scanner and FLACS program. We can quantify the explosive power by LPG gas accident and predict the gas leakage amount, damage by accident and evaluate the stability of the structure through this study. In the future, This method can be widely used in the field of gas safety by improving the reliability and validity of the analysis.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권1호
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• pp.110-116
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• 2016

In this study an attempt has been made to study the hydrodynamic performance of pumpjet propulsor. Numerical investigation based on the Reynolds Averaged NaviereStokes (RANS) computational fluid dynamics (CFD) method has been carried out. The structured grid and SST ${\kappa}-{\omega}$ turbulence model have been applied. The numerical simulations of open water performance of marine propeller E779A are carried out with different advance ratios to verify the numerical simulation method. Results show that the thrust and the torque are in good agreements with experimental data. The grid independent inspection is applied to verify accuracy of numerical simulation grid. The numerical predictions of hydrodynamic performance of pumpjet propulsor are carried out with different advance ratios. Results indicate that the rotor provides the main thrust of propulsor and the balance performance of propulsor is generally satisfactory. Additionally, the curve of propulsor efficiency is in good agreement with experimental data. Furthermore, the pressure distributions around rotor and stator blades are reasonable. Beyond that, the existence of tip clearance accounts for the appearance of tip vortex that leads to a further loss in efficiency and a probability of cavitation phenomenon.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.120-124
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• 2007

Helicopters and rotary-wing vehicles encounter a wide variety of complex aerodynamic phenomena and these phenomena present substantial challenges for computational fluid dynamics(CFD) models. This investigation presents the rotor aerodynamic analysis items for the helicopter development and variety aerodynamic analysis methods to provide the better solution to researchers and helicopter developers between aerodynamic problems and numerical aerodynamic analysis methods. The numerical methods to make an analysis of helicopter rotor are as below - CFD Modelling : actuator disk model, BET model, fully rotor model,... - Grid : sliding mesh, chimera mesh / structure mesh, unstructure mesh,... - etc. : panel method periodic boundary, quasi-steady simulation, incompressible,... The choice of CFD methodology and the numerical resolution for the overall problem have been driven mostly by available computer speed and memory at any point in time. The combination of the knowledge of aerodynamic analysis items, available computing power and choice of CFD methods now allows the solution of a number of important rotorcraft aerodynamics design problems.

• 한국전산유체공학회지
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• 제12권4호
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• pp.54-60
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• 2007

A theoretical and numerical investigation is performed on the flow in a micronozzle for precision-controlled sealant dispenser. The working fluid is a highly viscous epoxy used as sealant in producing LCD panels, which contains a number of tiny solid spacers. Flow analysis is conducted in order to achieve the optimal design of internal geometry of a nozzle. A simplified design analysis methodology is proposed for predicting the flow in the nozzle based on the assumption that the Reynolds number is much less than O(1). The parallel numerical computations are performed by using a CFD package FLUENT. Comparison discloses that the theoretical model gives a good prediction on the distribution of pressure and wall shear stress in the nozzle. However, the theoretical model has a difficulty in predicting the maximum wall shear stress as found in a limited region near edge by numerical computation. The theoretical and numerical simulations provide the good guideline for designing a dispensing micronozzle.

• 한국전산유체공학회지
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• 제14권4호
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• pp.56-61
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• 2009

This study deals with the numerical investigation on two-dimensional lubrication characteristics of micro-dimple shapes fabricated on solid surfaces by using the commercial CFD code (Fluent V.6.3) to examine the influence of micro dimple depth and width on the reduction in friction under the sliding plate condition. In addition, single and multiple dimple arrays are simulated, all for a fixed area fraction of dimple on the surface. As a result, it is found that the existence of micro-dimpled surface makes it possible to substantially reduce the friction forces exerted on the surfaces, and such an optimum dimple depth would be present because the dimple depth larger than the optimum value did no longer affect the reduction in shear stresses, indicating that the reduction of friction is likely to be associated with inner flows of lubricant inside dimples. Moreover, it is observed that at the fixed area fraction, the friction reduction increases with the increase of dimple diameter.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.27-36
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• 2020

Natural convection and thermal stratification phenomena are found in large water pools that are being used as heat sinks for decay heat removal from the reactor core using passive heat removal systems. In this study, the two-phase (water and air) natural convection and thermal stratification phenomena with conjugate heat transfer in the rectangular enclosure were investigated numerically using ANSYS Fluent 17.2 code. The transient numerical simulations of these phenomena in the full-scale computational domain of the experimental facility were performed. Generation of water vapour bubbles around the heater rod and evaporation phenomena were included in this numerical investigation. The results of numerical simulations are in good agreement with experimental measurements. This shows that the natural convection is formed in region above the heater rod and the water is thermally stratified in the region below the heater rod. The heat from higher region and from the heater rod is transferred to the lower region via conduction. The thermal stratification disappears and the water becomes well mixed, only after the water temperature reaches the saturation temperature and boiling starts. The developed modelling approach and obtained results provide guidelines for numerical investigations of thermal-hydraulic processes in the water pools for passive residual heat removal systems or spent nuclear fuel pools considering the concreate walls of the pool and main room above the pool.

• Advances in biomechanics and applications
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• 제1권3호
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• pp.143-158
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• 2014

Forearm fractures in children are very common among all pediatric fractures. However, biomechanical investigations on the pediatric forearm are rather scarce, partially due to the complex anatomy, closely situated, interrelated structures, highly dynamic movement patterns, and lack of appropriate tools. The purpose of this study is to develop a computational tool for child forearm investigation and characterize the mechanical responses of a backward fall using the computational model. A three-dimensional 10-year-old child forearm finite element (FE) model, which includes the ulna, radius, carpal bones, metacarpals, phalanges, cartilages and ligaments, was developed. The high-quality hexahedral FE meshes were created using a multi-block approach to ensure computational accuracy. The material properties of the FE model were obtained by scaling reported adult experimental data. The design of computational experiments was performed to investigate material sensitivity and the effects of relevant parameters in backward fall. Numerical results provided a spectrum of child forearm responses with various effective masses and forearm angles. In addition, a conceptual L-shape wrist guard design was simulated and found to be able to reduce child distal radius fracture.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.638-641
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• 2008

Computational investigation was conducted to study the effects of the shape parameter of shroud on the performance of the outdoor unit of an air-conditioners. For this study the Design of Experiment(4-factor 3-level) was created and the an automatic program was composed using VBA to reduce the load of pre-process for CFD. The estimated mathematical equation was produced from this analysis and it was found that the gap between fan and shroud affects more heavily than the other parameters. As a result, the composition of the best parameters was verified that its flow rate was increased by 10 percents and sound pressure level was reduced by 1.2 dBA compare with the worst. And finally, a kind of Propeller fan with blades which were attached to the shroud, so-called 'ProBeller Fan' was introduced in this study.

• 대한설비공학회지:설비저널
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• 제13권2호
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• pp.10-15
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• 1984

The aims of this study are to obtain a suitable method and a proper mesh for investigation of the temperature distribution and heat transfer. The relative errors of temperature distribution and heat transfer for each mesh are acquired in accordance with linear finite element (FEM 3), square finite element (FEM 6), cubic finite element (FEM 10), and finite difference method (FDM). It has been found that FEM 10 is the most accurate measure to obtain the temperature distribution and heat transfer. However, no significant results have been obtained successfully, because when higher order finite element methods are used the more computational efforts are necessary due to the distribution of elements. The results of this study are as follows ; 1 . In case of a=b=L, meshes for less than $1\%$ relative errors (temperature distribution) acquired in various methods to exact solution are $2\times2,\;4\times4,\;8\times8\;and\;8\tiems8$ for each FEM 10, FEM 6, FEM 3 and FDM and a=L, b=1/2L are $10\times5$ for each FEM 3 and FDM. And the tendency of results acquired of heat transfer is similar to those above. 2 . In computational efforts (a=b=L), FEM 6 has taken 21 times. and FEM 10 154times FEM 3 and FDM and FEM 3 is the sane as FDM.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.742-753
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• 2008

Currently an increasing number of urban tunnels with small overburden are excavated according to the principle of the New Austrian Tunneling Method (NATM). Therefore, a possibility of a tunnel collapse during excavation is getting higher in a proportionate manner. This paper will analyze causes the failure mechanism of a shallow NATM tunnel for different geological conditions, ground-water and invert solutions by investigation typical collapse site during tunnel construction. In this paper, this analysis performed two phase, firstly, the field investigation considering displacement measurement, ground-water level, geological characteristic, secondly, the numerical simulation considering the exist of invert construction and the effect of ground-water. It has been found that environmental factors such as state of underground water or construction sequences could influence failure mechanism of a shallow tunnel.