• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.12 no.2
• /
• pp.21-33
• /
• 1992

Under the intense-impulsive loading, structures are subjected to the wide range of pressures at an instantaneous time. The constitutive laws capable to describe the material behavior under the extreme pressure as well as the low pressure are necessary for the analysis of the structural behavior under the intense -impulsive loadings. In this study, two plastic models, the pressure independent Von-Mises model and the pressure dependent Drucker-Prager model, are employed for the wave propagation analysis. Governing equations of this study are conservation equations of momentum and mass in Lagrangian coordinate system which is fixed to the material. Due to the shock-front which violates the continuity assumptions inherent in the differential equations numerical artificial viscosity is used to spread the shock front over several computational zones. These equations are solved by Finite Difference Method with discretized time and space coordinates. The associate normality flow rule as a plastic theory is implemented to find the plastic strains.

• Journal of architectural history
• /
• v.13 no.4 s.40
• /
• pp.7-18
• /
• 2004

From the results of an examination of the transition process of the site plan divided into 5 stages based on literature and materials relating to the Sangju Confucian School as well as the construction history, we can see the general transition flow as follows. The arrangement form of Sangju Confucian School shows the structures with both the sacrificial rites function and the learning function in the early period. This shows a large general flow where the form with the learning function structure at the front and sacrificial rites function structure at the back changed to a form where the learning function structure was positioned behind the boarding facilities, after which there was a transformation which left only the learning function (the form where the learning function structure was positioned in front of the boarding facilities). The type where the learning function structure is positioned in front of the boarding facilities is hard to find in the Yeongnam area, also, there are not many examples of the 2 story Myeonglyundang (hall of confucianism teachings) throughout the country Sangju Confucian School which possess the value of rarity is appraised as being a precious material showing another area characteristic in Sangju of the Yeongnam area. Also, during the late Chosun period the scale of the Dongseojae (boarding facility) was reduced and the appearance of Yangsajae can be said to be a typical example of confucian school constructions of late Chosun era.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2540-2545
• /
• 2007

A computational study of BLDC motor is presented to elucidate thermo-flow characteristics in winding and bearing with heat generation. Rotation of rotor and blades drives influx of ambient air into the rotor inlet and the inflow rates are predicted more at the front-side inlet than at the rear-side, which can be ascribed to the different pressure distribution. Recirculation zone appears in the tiny interfaces between windings, however, showing the enhanced cooling performance due to the higher velocity distribution near the rotor wall. In contrast, flow separation and incline angle of bearing groove, and relatively slower velocity distribution cause poor cooling performance and therefore the redesign of the bearing groove is significantly required.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.3056-3061
• /
• 2007

The technology of AC solenoid valves is now considered as a core technology in the fields of the production line of semi-conductor chips and the micro fluid chips for medical applications. And AC solenoid valves, which operate by compressed air, are characterized by high speed response, great repeatability and that the pressure on the cross sectional area of poppet is kept constant regardless of the fluctuation of the pressure exerted on the ports. In this study, AC solenoid valves that posses the high-speed responsibility and the high rate of flow have designed and analyzed through the law of equivalent magnetic circuit and Finite Element Method (FEM) respectively. In case of poppet, Flow field characteristic was analyzed by the variation of poppet and it was able to display flow field by changing the location of the poppet. Also, we verified possibility of the design through the static and dynamic pressure and the 3D distribution curve of the force by working the front poppet.

• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.305-310
• /
• 2001

This paper presents the computational method for analyzing the compressible flow fields in a high voltage gas circuit breaker. There are many difficult problems in analyzing the gas flow in GCB due to complex geometry, moving boundary, shock wave and so on. In particular, the distortion problem of the grid due to the movement of moving parts can be worked out by the fixed grid technique. Numerical simulations are based on a fully implicit finite volume method of the compressible Reynolds-averaged Navier-Stokes equations to obtain the pressure, density, and velocity through the entire interruption process. The presented method is applied to the real circuit breaker model and the pressure in front of the piston is good agreement with the experimental one.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.9 no.5
• /
• pp.148-156
• /
• 2001

Computational Fluid Dynamics (CFD) analysis was carried out to investigate exhaust gas flow and acoustic characteristics in the exhaust system of a passenger car. Transient 3-dimensional flow field in the front and rear mufflers was simulated by CFD and far-field sound pressure was modeled by a simple monopole source method. Engine performance simulation was also performed to obtain the boundary condition of instantaneous fluid flow variation at the inlet of the exhaust system. Detailed exhaust gas flow characteristics such as velocity and pressure distribution inside the mufflers were presented and the pulsating pressure amplitude was compared at several positions in the exhaust system to deduce sound pressure level. The present method of the acoustic analysis coupled with CFD techniques would be very effective for the prediction of sound noise from vehicle exhaust systems although the effects of the inlet boundary condition and heat transfer on the accuracy of the prediction have to be validated through further studies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2008.11a
• /
• pp.570-575
• /
• 2008

Flows are studied to understand the flow structure in the narrow region that any experimental approaches are hard to access, Effects on the vehicle commodities from the flows are anticipated in the point of aerodynamics and aero-acoustics. PowerFLOW, which was well validated commercial software, was used to simulate the flow field in the small region, for example, the inner region of the fender panel, the inner region around the front door and the inner region of the trunk lid. Flows in the narrow region could be origins of door sealing problem and dust piling problem.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.11
• /
• pp.57-64
• /
• 2005

Large Eddy Simulation (LES) of turbulent premixed combustion flow is performed by using the dynamic subgrid scale model based on -equation describing the flame front propagation. After introducing the LES governing equations with dynamic subgrid scale (DSGS) model newly introduced into the -equation, the turbulent premixed combustion flow over backward facing step is analyzed to validate present formulation. The calculated results can predict the velocity and temperature of the combustion flow in good agreement with the experiment data.

• Communications of the Korean Mathematical Society
• /
• v.15 no.1
• /
• pp.155-172
• /
• 2000

Mode interactions at Unstable fluid interfaces induced by a shock wave (Richtmyer-Meshkov Instability) are studied both analytically and numerically. The analytical approach is based on a potential flow model with source singularities in incompressible fluids of infinite density ratio. The potential flow model shows that a single bubble has a decaying growth rates at late time and an asymptotic constant radius. Bubble interactions, bubbles of different radii propagates with different velocities and the leading bubbles grow in size at the expense of their neighboring bubbles, are predicted by the potential flow model. This phenomenon is validated by full numerical simulations of the Richtmyer-Meshkov instability in compressible fluids for initial multi-frequency perturbations on the unstable interface.

• 한국전산유체공학회:학술대회논문집
• /
• 1998.11a
• /
• pp.1-6
• /
• 1998

From surface flow visualization on a MIRA notchback reference model using oil flow technique, the topology of the singular points of the skin friction lines are delineated. Separation and reattachment lines at the front screen, at the A-pillar, at the C-pillar and on the rear side of the car including the trunk have been identified. It is worth to mention that two vortices emerging from the top of the trunk coil in the opposite direction as that vortices starting from the C-pillar edge. The positions of the singular points and the separation and reattachment lines and the foci of the vortices provide a sensitive database for validation of CFD-codes