• Journal of Mechanical Science and Technology
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• 제16권2호
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• pp.262-269
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• 2002

The effects of velocity boundary conditions on the structure of methane-air nonpremixed counterflow flames were investigated by two-dimensional numerical simulation. Two low global strain rates, 12 s$\^$-1/ and 20 s$\^$-1/, were considered for comparison with measurements. Buoyancy was conformed to have strong effects on the flame structure at a low global strain rate. It was shown that the location where a top hat velocity profile was imposed is sensitive to the flame structure, and that the computed temperature along the centerline agrees well with the measurements when plug flow was imposed at the inner surface of the screen nearest the duct exit.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.663-666
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• 2002

Hard disk drived (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. The distribution of pressure disturbance on disks has relation to flow structure. To investigate the flow structure, time-resolved hot-wire measurements of the circumferential velocity component were obtained for the flow between the center pair of four disks of common radius $R_2$ coretating at angular velocity ${\Omega}$ in a fixed cylindrical enclosure. Hot-wire supporter acts as an obstruction in this case. The effects of rotating speed and size of hot-wire supporter diameter between disks on the flow driven by disks were investigated. Velocity spectra at the fixed space were measured to obtain the structure of inner and outer region in flow field.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.236-239
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• 2014

Most naval underwater weapon system can be simplified to a circular cylindrical structure which has vibrating machineries inside. In order to predict efficiently the total acoustic radiation power of cylindrical structure, surface velocity is measured and radiation efficiency of surface element is calculated. Then, they are substituted to the surface pressure in the simplified Helmholtz integral equation which assumes acoustic far-field and plane-wave approximation at the surface. Surface velocity and total acoustic radiation power for a submerged cylinder are measured in water-tank. In this example, it is found that total acoustic power output obtained from the prediction is in good agreement with that of measurement in mid-high frequency range.

• 한국연소학회지
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• 제19권1호
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• pp.17-28
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• 2014

In this study, the laminar burning velocity of syngas fuel($H_2/CO$) and flame structure with various hydrogen contents were studied using both experimental measurements and detailed kinetic analysis. The laminar burning velocities were measured by the angle method of Bunsen flame configuration and the numerical calculations including chemical kinetic analysis were made using CHEMKIN Package with USC-Mech II. A wide range of syngas mixture compositions such as $H_2$ : CO = 10 : 90, 25 : 75, 50 : 50, 75:25 and equivalence ratios from lean condition of 0.5 to rich condition of 5.0 have been considered. The experimental results of burning velocity were in good agreement with previous other research data and numerical simulation. Also, it was shown that the experimental measurements of laminar burning velocity linearly increased with the increment of $H_2$ content although the burning velocity of hydrogen is faster than the carbon monoxide above 10 times. This phenomenon is attributed to the rapid production of hydrogen related radicals such as H radical at the early stage of combustion, which is confirmed the linear increase of radical concentrations on kinetic analysis. Particular concerns in this study are the characteristics of burning velocity and flame structure different from lean condition for rich condition. The decrease of OH radicals and double peaks are observed with $H_2$ content in rich condition once $H_2$ fraction exceeds over threshold.

• 지구물리
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• 제9권3호
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• pp.231-240
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• 2006

The crustal structure of the Korean Peninsula was investigated by analyzing phase velocity dispersion data of Rayleigh waves. Earthquakes recorded by three component broad-band velocity seismographs during 1999-2004 in South Korea were used in this study. The fundamental mode Rayleigh waves were extracted from vertical components of seismograms by multiple filter technique and phase match filter method. Phase velocity dispersion curves of the fundamental mode signal pairs for 14 surface wave propagation paths on the great circle in the range 10 to 80 sec were computed by two-station method. Treating the shear velocity of each layer as an independent parameter, phase velocity data of Rayleigh wave were inverted. All the result models can be explained by a rather homogeneous crust of shear-wave velocity increasing from 2.8 to 3.25 km/sec from top to about 33 km depth without any distinctive crustal discontinuities and an uppermost mantle of shear-wave velocity between 4.55 and 4.67 km/sec. Our results turn out to agree well with recent study of Cho et al. (2006 b) based on the analysis of seismic background noises to recover short-period (0.5-20 sec) Rayleigh- and Love-wave group velocity dispersion characteristics.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.969-974
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• 1994

The dynamic behavior of graphite/epoxy laminated composite shell structure due to low-velocity impact is investigated using the finite element method. In this analysis, the Newmark's constant-acceleration time integration algorithm is used. The impact response such as contact force, central deflection and dynamic strain history form shell structure analysis are compared with those form the plate non-linear analysis. The effects of curvature, impact velocity and mass of impactor on the composite shell are discussed.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제33회 KOSCO SYMPOSIUM 논문집
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• pp.145-150
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• 2006

At the furnace top, the distribution of charging coke and ore is adjusted to control the reducing gas flow distribution in the furnace. It is necessary to predict operation condition of blast furnace according to the burden profile to judge whether charging is properly conducted In this study, We propose the model for predicting while layer structures whithin furnace when top burden profile was given. Layer structure of coke and ore could be predicted by top burden profile and solid velocity. Solid velocity is assumed as potential flow. Potential function distribution and timeline are also calculated using solid velocity field. The Calculation is conducted for different burden profile cases. As the result burden distribution and grid structure, which is deformed to match the layer structure in shaft and deadman profile. Gas flow was calculated using this grid, and calculated results are compared with each other.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.21-26
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• 2007

This study focuses on the near-field vortical structure and dynamics of coaxial jets. The characteristics of laminar flow and mixing in coaxial jets are investigated using a unsteady flow simulation. In order to analyze the geometic effects on the vortical structure, several cases of different configurations are selected for various values of the velocity ratio of inner jet to outer jet. From the result, it is confirmed that mixing is promoted by the development of vortical structure and the interaction between inner jet and outer jet. This feature is strongly related to the vortex frequency in the shear-layers. The vortex frequency depends on the velocity ratio and the lip thickness of inner nozzle, but the outer pipe length has no effect on the frequency variation.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1666-1673
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• 1997

In order to investigate the characteristics of sound-structure interaction plate having a cut-out, we modeled a rectangular cavity and the flexible plate of the cavity. Because the particle velocity of air is the same as that of plate on the plate, we could easily redefine vibration equation using the velocity potential. We calculated the natural frequencies of plate using orthogonal polynomial functions which satisfy the boundary conditions in the Rayleigh-Ritz method. For the change of vibration characteristics, the effect of sound-structure interaction is more dominant than that of cut-out size.

• 한국전산유체공학회지
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• 제14권3호
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• pp.49-55
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• 2009

This study focuses on the near-field vortical structure and dynamics of coaxial jets. The characteristics of laminar flow and mixing in coaxial jets are investigated using a unsteady flow simulation. In order to analyze the geometric effects on the vortical structure, several cases of different configurations are selected for various values of the velocity ratio of inner jet to outer jet. From the result, it is confirmed that the flow mixing is promoted by the development of vortical structure and the interaction between inner jet and outer jet. This feature is strongly related to the vortex frequency in the shear-layers. The vortex frequency depends on the velocity ratio and the lip thickness of inner nozzle, but the outer pipe length has no effect on the frequency variation.