• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.4
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• pp.280-286
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• 2002

It has been long suspected that the transition region may give rise to local pressure fluctuations and radiated sound that are different from those created by the fully-developed turbulent boundary layer at equivalent Reynolds number. Experimental investigation described in this paper concerns the characteristics of pressure fluctuations at the transition. Flush-mounted microphones and hot wires are used to measure the pressure fluctuations and local flow velocities within the boundary layer in the low noise wind tunnel. From this experiment we could observe the spatial and temporal development process of T-S wave using Wigner-Ville method and find the relations between the characteristic frequency of T-S wave and free stream velocity and the boundary layer thickness based on nondimensional pressure spectra scaled on outer variables.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.1
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• pp.91-96
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• 2014

The aim of this work is to determine supersonic nozzle profiles that are used in propulsion, for launchers or embarked with satellites. This design has the role of firstly, providing important propulsion, i.e. with uniform and parallel flow at exit; and secondly, to find short length profiles, without modification of the flow in the nozzle. The first elaborate program is used to determine the profile of the divergent, by using the characteristics method for an axisymmetric flow. The second program is conceived by using the finite volume method, to determine and test the profile found connected to a convergent.

• Journal of the Korean Society of Combustion
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• v.19 no.2
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• pp.1-7
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• 2014

In this study, the variation of the flow field in Hydro-reactive engine combustor was numerically studied through 2-dimensional axisymmetric model with aluminum and heated water vapor. For calculating all velocity fields, compressible Navier-Stokes equation was used with Pre-conditioning. AUSM+up(p) method was used to exactly calculate mass flow in the control volume. As using SST model that is a turbulent model, the result had high accuracy for free stream and the flow near the wall. The effects of the temperature, variation of the flow field and distribution of chemical products on inject angle of heated water vapor were studied.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.562-567
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• 2000

The Impingement of a weak shock wave discharged from the open end of a shock tube upon a flat plate was investigated using shock tube experiments and numerical simulations. Harten-Yee Total Variation Diminishing method was used to solve axisymmetric, unsteady, compressible flow governing equations. Experiments were carried out to validate the present computations. The effects of the flat plate and baffle plate sizes on the impinging flow field over the flat plate were investigated. Shock Mach number was vaned in the range from 1.05 to 1.20. The distance between the plate and shock tube was changed to investigate the effect on the peak pressure. From both the results of experiments and computations we obtained a good empirical equation to predict the peak pressure on the flat plate.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.91-94
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• 2004

A numerical analysis was made to investigate the intensity diminution of a simple silencer for high pressure blast flow fields. Reynolds-Averaged Wavier-Stokes equations were solved for an axisymmetric computational domain constructed by multi block Chimera grids. A blast flow field without the silencer was also calculated to validate the present numerical method. The evolution of high pressure blast flow fields was observed by depicting calculated contours of pressure and Mach number. It was found that the tested silencer could achieve 76 percent intensity diminution.

• Wind and Structures
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• v.19 no.1
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• pp.89-111
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• 2014

The dynamics of a tornado-like vortex with touching down is investigated by using the LES turbulence model. The detailed information of the turbulent flow fields is provided and the force balances in radial and vertical directions are evaluated by using the time-averaged axisymmetric Navier-Stokes equations. The turbulence has slightly influence on the mean flow fields in the radial direction whereas it shows strong impacts in the vertical direction. In addition, the instantaneous flow fields are investigated to clarify and understand the dynamics of the vortex. An organized swirl motion is observed, which is the main source of the turbulence for the radial and tangential components, but not for the vertical component. Power spectrum analysis is conducted to quantify the organized swirl motion of the tornado-like vortex. The gust speeds are also examined and it is found to be very large near the center of vortex.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.1
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• pp.28-36
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• 1990

In this paper, the flow field with steady, axisymmetric flow characteristics in cylinder has been numerically investigated. The prediction of flow in cylinder was compared to experimental result. The turbulence closure being applied was K-${\epsilon}$ model and numerical scheme was Hybrid and Power-law scheme. The results of numerical computation showed some deviation from exper- imental data in the in cial region of cylinder, where streamline curvature is significant. However, the computational results agree qualitatively well with Mores's experimental results and the difference between Hybrid and Power-law schows similar results

• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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• pp.125-130
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• 1996

A numerical analysis is conducted on heat transfer and fluid flow of a plasma spraying process under the DC-RE hybrid electromagnetic field. Plasma flow is analyzed by using Eulerian approach and the equation of particle motion is simultaneously solved using a trajectory analysis with a lumped-heat-capacity model. Axisymmetric two dimensional electromagnetic fields governed by Maxwell's equations are solved based on a vector potential concept. The effects of the RF electromagnetic field on the temperature and velocity fields of the turbulent plasma flow are clarified. Control characteristics of phase changes and dispersed features of particles by applying the RF electromagnetic field are also clarified in an attempt to improve the plasma spraying process

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.169-172
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• 2005

A numerical analysis was made In investigate the pressure diminution of a silencer with baffles for high pressure blast flow fields. Reynolds-Averaged Navier-Stokes equations were solved for an axisymmetric computational domain constructed by multi block Chimera grids. A blast flow field was calculated for the silencers that are with one and three baffles. The evolution of high pressure blast flow fields was observed by depicting calculated contours of pressure. It was found that the tested silencer could achieve 97.7 percent pressure diminution.

• International Journal of Automotive Technology
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• v.5 no.1
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• pp.17-22
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• 2004

An experimental investigation was conducted to study the characteristics of turbulent swirling flow in an axisymmetric annuli. The swirl angle measurements were performed using a flow visualization technique using smoke and dye liquid for Re=60,000-80,000. Using the two-dimensional Particle Image Velocimetry method, this study found the time-mean velocity distribution and turbulence intensity in water with swirl for Re=20,000, 30,000, and 40,000 along longitudinal sections. There were neutral points for equal axial velocity at y/(R-r)=0.7-0.75, and the highest axial velocity was recorded near y/(R-r)=0.9. Negative axial velocity was observed near the convex tube along X/(D-d)=3.0-18.0 for Re=20,000.