• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.481-487
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• 2005

A turbopump turbine consists of rotational part including a rotor and stationary part including nozzles and exit guide vanes, of which shape and relative position affect turbine performance owing to supersonic flows with prevailing unsteadiness. In this study, numerical 3-D flow calculations of the turbine with the different number of exit guide vanes and different relative position of each component are conducted and the effect of flow passage variations on turbine performance is analyzed.

• Wind and Structures
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• v.1 no.3
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• pp.271-284
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• 1998

This paper uses the numerical simulation to investigate the interference effect of 3-D turbulent flow around two high rise buildings in proximity at the different relative heights, gaps, and wind velocities. The computer program used to carry out the simulation is based on the control volume method and the SIMPLEST algorithm. The ${\kappa}-{\varepsilon}$ model was used to simulate turbulence effects. Since the contracted flow between two adjacent buildings enhances the strength of vortex shedding from the object building, the pressure coefficient on each side wall of the object building is generally increased by the presence of apposed building. The effect is increased as the relative height or the gap between the two buildings decreases. The velocity on the vertical center line between two buildings is about 1.4 to 1.5 times the upstream wind velocity.

• Journal of Power System Engineering
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• v.6 no.4
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• pp.16-22
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• 2002

This study was conducted to find performance evaluation method for automobile air conditioner. Experimental facilities were constructed to simulate wide range of operating condition for the automobile air conditioner. Compressor speed was controled by variable speed electric motor and the power was measured through torque transducer and tachometer was used to measure compressor speed. Parametric studies were conducted in this study, to figure out effect of environment variables on the performance of the automobile air conditioner. The environmental variables are inlet air temperature, relative humidity and air flow rate for the evaporator and inlet air temperature and air flow rate for the condenser. Compressor speed is also changed. The results of this study shows that air flow rate of the evaporator is more sensitive to the performance of the automobile air conditioner than the other variables. However relative humidity of the inlet air of the evaporator strongly affects capacity rather that COP.

• Journal of Drive and Control
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• v.16 no.2
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• pp.66-71
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• 2019

In this study, flow analysis and dehumidification experiments were performed on hollow fiber membrane module to confirm the dehumidification characteristics for its different configurations. The CFD for the three different models was conducted using $30^{\circ}C$ temperature and 30%RH inlet humidity for quantitative analysis. Each model has different shape parameters i.e. the number of baffles. Comparison between flow analysis results and dehumidification experiment results revealed a percentage error of about 5%. The difference in relative humidity between the inlet and outlet for each model was calculated using flow analysis data. It was established that the difference in relative humidity of the inlet and outlet for the refined model with three baffles was highest among the three modeled modules of hollow fiber membrane module, i.e. around 9%.

• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1869-1875
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• 2001

The paper presents computational and flow visualization results on a centrifugal blood pump. 4 impeller designs were tested at a rotational speed of 2000 rpm using blood analog as working fluid. All impellers have seven blades but of different geometry (Impellers A3, A4, B2 and R7). Flow visualization within the impeller passages was conducted using an image de-rotation system. A pair of large scale vortices was found within the blades of impeller R7 while a single vortex was found in most of the passages of backward facing impellers (Impellers A3, A4 and B2). To establish the effects of blade geometry on blood cells, CFD was used to simulate the blade to blade flow to provide an estimate of the maximum shear stress. The results showed that though most of the stresses within the blade passages are below a threshold level of 150 N/m$^2$for extensive erythrocyte damage to occur, there are some regions near to the leading edge of the pressure side where the shear stresses a abode threshold level.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.10 s.115
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• pp.1082-1089
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• 2006

In this study, advanced computational analysis system has been developed in order to investigate flow-induced vibration(FIV) phenomenon for general stator-rotor cascade configurations. Relative movement of the rotor with respect to stator is reflected by modeling Independent two computational domains. Fluid domains are modeled using the unstructured grid system with dynamic moving and local deforming methods. Unsteady, Reynolds-averaged Wavier-stokes equations with one equation Spalart-Allmaras and two-equation SST ${\kappa}-{\varepsilon}$ turbulence models are solved for unsteady flow problems and also relative moving and vibration effects of the rotor cascade are fully considered. A coupled implicit time marching scheme based on the Newmark integration method is used for computing the governing equations of fluid-structure interaction problems. Detailed vibration responses for different flow conditions are presented and then vibration characteristics are physically investigated in the time domain as computational virtual tests.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.221-226
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• 2000

In this study, the characteristics of gas-water relative permeability curves in a single fractured-plate according to the various aperture size were analyzed by using the Hele-Shaw type glass plate model. The plate was made of glasses for the observation of the two-phase flow pattern, and seven cases were set up based on the aperture size in the range of field scale from 30 to $120\mum$. The experiment was conducted by steady-state method, and the water saturation was determined more accurately by the developed digital image process technique. The empirical equations of relative permeability to gas and water for single fractured-plate were correlated by using the aperture size which directly affects the two-phase flow pattern and critical saturation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.8
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• pp.677-682
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• 2015

We simulate an emulsion system under simple shear rates to analyze its rheological characteristics using the lattice Boltzmann method (LBM). We calculate the relative viscosity of an emulsion under a simple shear flow along with changes in temperature, shear rate, and surfactant concentration. The relative viscosity of emulsions decreased with an increase in temperature. We observed the shear-thinning phenomena, which is responsible for the inverse proportion between the shear rate and viscosity. An increase in the interfacial tension caused a decrease in the relative viscosity of the decane-in-water emulsion because the increased deformation caused by the decreased interfacial tension significantly influenced the wall shear stress.

• Journal of computational fluids engineering
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• v.20 no.1
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• pp.1-9
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• 2015

A developed code is applied to simulate relative motion of floating bodies in a side-by-side arrangement, including effects of a fender and a hawser. The developed code is based on the flux-difference splitting scheme for immiscible incompressible fluids and the hybrid Cartesian/immersed boundary method. To validate the developed code for free surface flows around deforming boundaries, the water wave generation is simulated, which is caused by bed movement. The computed wave profile and time histories of wave elevation are compared with other experimental and computational results. The effects of a fender and a hawser are modeled by asymmetric force acting on the floating bodies according to a relative displacement with the bounds, in which the fender and the hawser exert no force on the bodies. It has been observed that the floating body can be accelerated by a gap flow due to a phase difference caused by the free surface. Grid independency is established for the computed time history of the body velocity, based on three different size grids.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.450-455
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• 2001

The time-dependent behavior of nonequilibrium condensation of moist air through the Ludwieg tube is investigated with a computational fluid dynamics(CFD) method. The two-dimensional, compressible, Navier-Stokes equations, fully coupled with the condensate droplet growth equations, are numerically solved by a third-order MUSCL type TVD finite-difference scheme, with a second-order fractional time step. Baldwin-Lomax turbulence model is employed to close the governing equations. The computational results are compared with the previous experiments using the Ludwieg tube with a downstream diaphragm. The results clearly show that for an initial relative humidity below 30% there is no periodic oscillation of the condensation shock wave, but for an initial relative humidity over 40% the periodic excursions of the condensation shock occurs in the Ludwieg tube, and the frequency increases with the initial relative humidity. It is also found that total pressure loss due to nonequilibrium condensation in the Ludwieg tube should not be ignored even for a very low initial relative humidity, and the periodic excursions of the condensation shock wave are responsible for the total pressure loss.