• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.11
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• pp.1449-1457
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• 1997

Since a non-nulling method of five-hole probes is valid only when the flow angle is within the calibrated angle range, it can not be used in a complex flow field. Full angle range pressure coefficient maps show that widely used nulling methods do not guarantee correct alignment of the probe with the flow direction in the unknown complex flow field. Zone decision method and features of zone map were studied by investigating the full angle range pressure coefficient maps. A reliable and efficient new nulling algorithm using zone decision by pressure ordering is proposed and verified. Since the zone decision method by pressure ordering can decide whether the flow is within the calibration angle range or not, it is useful in wide angle nonnulling methods, too.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.2
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• pp.116-116
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• 1996

This paper is concerned with a method for calibrating five-hole probes of both angle-tube and prismatic geometries to measure local total and static pressures and the magnitude and direction of the mean velocity vector. Descriptions of the calibration technique, the typical calibration data, and an accompanying discussion of the interpolation procedure are included. The flow properties are determined explicitly from measured probe pressures using calibration data. Flow angles are obtained within the deviation angle of 1.0 degree and dynamic pressures within 0.03 with 95% certainty. The variations in the calibration data due to Reynolds number are also discussed. For the range of Reynolds number employed, no effect was detected on the pitch, yaw and total pressure coefficients. However, the static pressure coefficient showed change to cause minor variations in the magnitude of the calculated velocity vector. To account for these variations, average correction factors need to be incorporated into the static pressure coefficient.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.2
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• pp.48-56
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• 1996

This paper is concerned with a method for calibrating five-hole probes of both angle-tube and prismatic geometries to measure local total and static pressures and the magnitude and direction of the mean velocity vector. Descriptions of the calibration technique, the typical calibration data, and an accompanying discussion of the interpolation procedure are included. The flow properties are determined explicitly from measured probe pressures using calibration data. Flow angles are obtained within the deviation angle of 1.0 degree and dynamic pressures within 0.03 with 95% certainty. The variations in the calibration data due to Reynolds number are also discussed. For the range of Reynolds number employed, no effect was detected on the pitch, yaw abd total pressure coefficients. However, the static pressure coefficient showed change to cause minor variations in the magnitude of the calculated velocity vector. To account for these variations, average correction factors need to be incorporated into the static pressure coefficient.

• Journal of Mechanical Science and Technology
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• v.14 no.5
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• pp.477-482
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• 2000

This study discusses a non-contact optical technique (electronic speckle pattern interferometry) that is well suited for thermal deformation measurement without any surface preparation and compensating process. Fiber reinforced plastics ($[0]_{16},\;[0/90]_{8S}$) were analyzed by ESPI to determine their thermal expansion coefficients. The thermal expansion coefficient of the transverse direction of a uniaxial composite is evaluated as $48.78{\times}10^{-6}(1/^{\circ}C)$. Also, the thermal expansion coefficient of the cross-ply laminate $[0/90]_{8S}$ is numerically estimated as $3.23{\times}10^{-6}(1/^{\circ}C)$ that is compared with that measured by ESPI.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.857-860
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• 2003

We introduced the basic direction of revision for KS F 2805 (method for measurement of sound absorption coefficient in a reverberation room). It is fundamentally equal to ISO 354 (measurement of sound absorption in a reverberation room) which was state of ISO/FDIS 354. Two main points were strongly reviewed. First, the sound absorption coefficient values for Type J test specimen mounting was investigated. Next, the reverberation time difference between the conventional method and new additional one, impulse response method were compared.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.2
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• pp.312-322
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• 2001

This paper investigates the combined effects of parameters such as die surface finish, die directionality of stoning contact pressure and draw speed on the resulting coefficient of friction. Also, this study show the correlation between the NN(Neural Network) and DOE(Design of Experiments) to reduce the number of experiments without the loss of the effects of parameter upon coefficient of friction. The experiments were run in random order with at least three replicates. It was found that the directional stoning orthogonal to the pulling direction is lower friction than directional stoning parallel to the pulling directi on using FCD55 die and SPCEN.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.187-196
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• 1988

Meander characteristics of the Han River System using autocorrelation coefficient and variance spectrum were analysed, and meander paths were simulated by direction and direction-change series in this paper. Better wavelength estimates are obtained from direction-change spectra, dominant wavelength had the increasing tendency in order tributaries of the North Han River System, the South Han River System and the Han River Downstream System. The meander characteristics of tributaries in the North Han River, the South Han River and the Han River Downstream System could be obtained from the results of direction and direction change spectra. Direction and direction-change autocorrelograms are generally of damped oscillatory form, and wavelengths estimated from direction-change autocorrelograms correlate closely with wavelength estimated from direction-change specta.

• Journal of Energy Engineering
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• v.29 no.1
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• pp.34-43
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• 2020

A study has been done for self-starting torque of vertical axis wind turbine blade. It is especially concentrated to evaluate the torque coefficient before starting rotation. Two different aerofoils(AMI903 and AMI904) are proposed to benchmark the possible best blade(supercritical airfoil) for self-starting performance. Torque coefficients in the tangential direction of rotation are given with respect to the angle of attack in terms of drag coefficient and lift coefficient. Torque coefficient shows that the effect of Reynolds number is minimal. The thicker blade(AMI904) between two different proposed airfoils has bigger torque coefficient, which is attributed to lower lift coefficient and higher drag coefficient.

• Water for future
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• v.28 no.1
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• pp.91-106
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• 1995

An investigation into the rainfall variability in time and space in the Nam River dam basin of Korea was made with use of the coefficient of variation and the correlation coefficient. The Nam River dam basin is a small mountainous watershed where the wind direction and orography are the dominant influences on the pattern and distribution of rainfall. It was found that the characteristics of rainfall distribution vary with elevation, position, wind direction. And in the three directions considered, it was found that there is the related formulation dependent on the distance between two stations. The resultrs of this study on the temporal and spatial characteristics of rainfall can be used in the design of raingauge networks, hydrological forecasting, and so on in the Nam River dam basin.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.1
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• pp.129-135
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• 2016

Various type of valves are manufactured for different industrial uses. Among them, check valves are used to allow fluid to flow in one direction but not in the opposite direction. There are many different types of check valves, but Y-shaped check valves are widely used these days. Not many studies have been carried out on Y-shaped check valves and the flow coefficients obtained through numerical analysis have the problem of low reliability. In order to solve this problem, this study performed flow analysis, flow-structure coupled analysis, and flow coefficient measurement experimentally, and through these analyses derived and verified the flow coefficients and assessed the structural safety based on numerical analysis.