• Journal of Advanced Marine Engineering and Technology
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• v.20 no.4
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• pp.412-412
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• 1996

To maintain high spacial accuracy and rapid CPU time in interpolating data from grid to random position or inversely in PIV, proposed many technuques are compared and discussed mainly in terms of interpolating error and computing time. And artificial PIV atmosphere data is furnished by CFD result. First, for interpolation from grid to random position, multiquadric method gives the highest accuracy with the longest CPU time and Taylor series expansion methods give reasonable accuracy with less calculating load. Secondly, the sub-pixel resolution analysis in estimating the coordinates of the maximum correlation coefficients essential in the grey level correlation PIV reveal that 8-neighbours 2nd-order least square interpolation gives utmost accuracy in terms of the real flow conditions.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.45-50
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• 2005

Characteristics of flows at T-junction duct with and without orifices are investigated in this paper. Experiments and PIV visualization were carried out for several flow rates. Two-dimensional PIV experimental apparatus was decided by numerical analysis. PIV visualization was also coded to visualize flow fields at junctions for two-dimensional case. For the PIV visualization system, Grey-Level Cross-Correlation particle tracking algorithm was used to calculate the flow fields. Vinyl chloride polymer particles of $100{\sim}150{\mu}m$ of diameter are used in this visualization. The PIV visualization results showed relatively good agreement with Experimental data.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.559-564
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• 1999

A particle image velocimetry is the representative technique for measuring flow velocities at whole field simultaneously. The present study adopted the PTV method for velocity acquisition in a square enclosure with initially isothermal fluid by using a general lamp-based sheet light source. The enclosure was composed of hot and cold vertical wall and was confined by two horizon-tal adiabatic walls. The drift velocities were measured and the drift was visualized by PTV for a rayleigh number of 5.28{\times}10^8.$ Obtained instant simulataneous velocity vectors show flow pattern and the result of horizontal velocity profile agree well with the numerical result.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.739-742
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• 2008

Surface Image Velocity (SIV) is a technique which measures the surface velocity of river by using the principle of Paticle Image Velocimetry (PIV). The technique is economical and efficient way to measure velocity in rivers. The present paper aims to apply the technique to three rivers in Korea. It uses pairs of river surface images taken with two digital-cameras and reference points and cross section data which were acquired through plane survey. The performance of SIV was verified with automatic cart on an experimental flume. The test revealed that average error was less than 10 %, which assures that SIV can be used to measure velocity accurately. When it was applied to rivers with low water levels or rough weather condition, however, it showed the error about 20 %. If the problems of SIV technique are settled down, it can be one of the most convenient and economical ways to measure water discharge anytime and anywhere. And then it would be helpful to river management as developing a real-time river information system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.12
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• pp.1165-1172
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• 2009

The laminar boundary layer along a streamwise corner formed by two flat plates intersecting at right angle is measured by using Particle Image Velocimetry(PIV) technique. The free stream velocity ranges from 2.96m/s to 3.0m/s. The angle of incidence of the corner is set to 1.2 degree providing slightly favourable pressure gradient to ensure a laminar flow in the corner region. A round shape leading edge is used and the length of the model is about 1000mm. In the bisector plane, the measurement data show separation type velocity profiles having an inflection point which is a typical characteristic of laminar corner boundary layers. As the distance away from the bisector plane increases, velocity profiles are found to change into the Blasius profile. The change completes around half length of the boundary layer thickness in the bisector plane away from the bisector plane along the plate. In the bisector plane, the growth characteristic of the boundary layer thickness and the approximate similarity of velocity profiles are confirmed from the measurement data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.567-575
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• 2013

A POD analysis based on time-resolved PIV measurements in a circulating water channel has been conducted to identify the skin friction reduction mechanism of outer-layer vertical blades. A recent PIV measurement indicated 2.73% and 7.95% drag reduction in the blade plane and the blade-in-between plane, respectively. In the present study, the influence of vertical blades array upon the characteristics of the turbulent coherent structures was analyzed by the POD method. It is observed that the vortical structures are cut and deformed by the blades array and that their temporal evolution is strongly associated with the skin-friction drag reduction mechanism in the turbulent boundary layer flow.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.113-119
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• 1998

An experimental study was carried out in a three-dimensional cubic cavity driven by 2-dimensional plane Poiseuille flow for three kinds of Reynolds number, $10^4$, 3 $\times$ $10^4$ and 5 $\times$ $10^4$ based on the cavity width and cavity inlet mean flow velcoity. Instant simultaneous velocity vectors at whole field were measured by 2-D PIV system. Laser based illumination and two-frame grey-level cross correlation algorithm are adopted. Severe unsteady flow fluctuation within the cavity are remarkable at above Re = 3 $\times$ $10^4$ Reynolds numbers and sheared mixing layer phenomena are also found at the region where inlet driving Poiseuille flow is collided with the clock-wise rotating main primary vortex at upper center area. Instant velocity profiles reveal that deformed forced vortex formation is observed throughout the separate two areas.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.05a
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• pp.165-170
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• 2000

A fundamental experimental study for a substitute proposal to super-speed craft propulsion system called underwater ram-jet propulsion by high pressure air ejection as driving force was investigated. for basic study of effect of ram-jet propulsion performances ismple underwater ram-jet flow field was established and PIV(Particle Image Velocimetry) method was adopted to analyse the jet-induced flow appearing at ram intake mixing chamber and nozzle. Some flow dynamics relating to the high-speed ejector effect were discussed for the basic understanding for the ram-jet propulsion principle.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.3
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• pp.36-42
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• 2000

A fundamental experimental study for an alternative proposal to super-speed craft propulsion system called underwater ram-jet propulsion by high pressure air ejection as driving force was investigated. For basic study of the effects of ram-jet propulsion performance, a simple underwater ram-jet flow field was established and PIV(Particle Image Velocimetry) method was adopted to analyse the jet-induced flow appearing at ram intake, mixing chamber and nozzle. Some flow dynamics relating to the high-speed ram-jet effect were discussed for the basic understanding of the its propulsion principle.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.683-686
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• 2008

To diagnose vascular diseases from the viewpoint of hemodynamics, detailed quantitative hemodynamic information of related blood flows with a high spatial resolution of tens micrometer and a high temporal resolution in the order of millisecond were required. For investigating the hemodynamic phenomena of vascular circulatory diseases, a new diagnosing technique combining a medical radiography and PIV method was newly developed. This technique consisted of a medical X-ray tube, an X-ray CCD camera, a shutter module for double pulse-type X-ray source, and a synchronizer. Through several preliminary tests, the feasibility of the angiographic PIV technique was verified. For in-vivo measurements to real blood flows, we developed tracer microcapsules which were optimized to this system by encapsulating a contrast material of iodine with a matrix material of PVA (polyvinylpyrrolidone). In near future, the angiographic PIV technique would be useful for diagnosing hemodynamic phenomena of vascular diseases and for their early detection.