• International Journal of Fluid Machinery and Systems
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• v.7 no.2
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• pp.54-59
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• 2014

Particle Image Velocimetry combined with developed image processing method is adopted to study the liquid-solid two phase flow in the centrifugal pump impeller with crystallization phenomenon. The tracer particle is used to follow the liquid phase, which has the diameter between 8 to $12{\mu}m$. The crystal particle precipitates from the sodium sulfate solution does change the wavelength of the laser, and which has great laser scattering characteristics. The diameter of the crystal particle is larger than $20{\mu}m$. Through calculating the diameter of the particles in the image, the tracer particle and the crystal particle can be distinguished. By analyzing the experimental result, the following conclusion has been obtained. During the delay period, there is not any crystal particle and the pump performance has not been changed. As the crystallization process begins, the crystal nuclei appears from the supersaturation solution and grows larger with temperature decreasing, which has the tendency of moving towards the pressure side. The characteristics of liquid-solid two phase flow with crystallization phenomenon in the pump are obtained according to analysis of experimental results, and some guiding advices are presented to mitigate the crystallization phenomenon in pump impeller.

• Journal of Ocean Engineering and Technology
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• v.24 no.1
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• pp.1-9
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• 2010

A series of experiments employing particle image velocimetry (PIV) technique was conducted to produce benchmark wave kinematics data for regular waves having four different wave slopes in 2-D wave tank. Water velocities and accelerations near the free surface of regular waves were computed from image pair obtained by PIV systems. With the measured wave velocity field, the wave accelerations were computed using a centered finite difference scheme. Both local and convective components of the total accelerations are obtained from experimental data. With increasing the wave slope, the horizontal velocity and the vertical accelerations near the wave crest obtained by PIV technique became larger than theoretical results, which are well-known phenomena of the wave nonlinearity. It is noted that the relative magnitude of convective acceleration to the local acceleration became larger with increasing wave slope.

• Journal of Korea Water Resources Association
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• v.39 no.2 s.163
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• pp.99-108
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• 2006

To describe the behavior of suspended-sediment particles in turbulent open-channel flows, the advection-diffusion equation or its simplified form has been used. Though this equation was derived upon several assumptions, only a few studies tried to evaluate the limit of the assumptions. The reason is that it is very difficult to measure turbulence in open-channel flows and to discriminate the velocities of water and sediment particles. The present study aims to measure the velocity profiles of water and sediment particles in open-channel flows by using PTV (Particle Tracking Velocimetry), a kind of PIV (Particle Image Velocimetry). The measured results showed that sediment particles moved slower than water tracers did in the outer region. In the present study, the amount of velocity-lag reached about $5\%$ of the mom flow velocity and the position of the maximum velocity-lag was $g/h\approx0.05\;(g^{+}=30\~50)$ The main cause of the velocity-lag of sediment particles seems that the sediment particles have larger density than water has. On the other hand, in the viscous sublayer, sediment particle has a larger velocity than water tracers. The reason of the inversion of velocity-lag may be due to the no-sleep condition of water at the solid boundaries.

• Journal of the Korean Geotechnical Society
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• v.27 no.7
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• pp.5-16
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• 2011

Digital image analysis techniques have been developed and utilized in the field of solid mechanics and fluid mechanics to measure the deformation and velocity of a target object. The deformation measurement systems based on Particle Image Velocimetry (PIV) and Digital Image Correlation (DIC) have been attempted in geotechnical testings (e.g., physical model tests) for observing the deformation of soils. The digital image analysis is influenced by image pattern of test materials, resolution of the used digital camera, target area, image analysis techniques, and analysis conditions. Therefore, optimal analysis conditions should be determined to obtain high quality results on soil deformations. In the present study, various influence factors on the digital image analysis were described and summarized. The optimizing procedure for high accurate results was then proposed. Finally, the applicability of the developed procedure was examined.

• Journal of Ocean Engineering and Technology
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• v.18 no.3
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• pp.1-7
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• 2004

Flaw visualization and velocity field measurement methods have practical applications in the various fluid engineering fields, such as mechanics, ships, and heat fluids. In this study, the basic principles and theoretical methods are used to establish an application technique of Particle Imae Velocimetry(abbreviated to PIV below). Accordingly, the measured results of velocity field distribution of a section inside the Circulating Water Channel (abbreviated to CWC below) are computed using the PIV is presented. The uniformity of velocity distribution of the section in CWC is confirmed, by comparing this PIV data with the existing current meter data. Also, in order to measure the flaw fields of surroundings of 2-dimensional cylinder in the CWC, the flaw visualization technique using the PIV is applied.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.4
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• pp.515-525
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• 2000

A new acoustic field visualization technique is introduced in this study. Small particles of which density is small enough to follow up the air used for the noise field visualization. In order to quantify the noise, PIV(Particle Imaging Velocimetry) has been constructed. When the driving frequency is in the vicinity of the resonance frequency of the simplified 2-dimensional muffler system, an acoustic streaming is shown and of which velocity distribution is obtained through PIV technique. It is experimentally proved that the present technique is able to visualize and quantify the acoustic fields.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.82.2-82.2
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• 2005

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.599-600
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• 2013

• Journal of the Society of Naval Architects of Korea
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• v.51 no.4
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• pp.311-320
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• 2014

Test uncertainty of a towed underwater Stereoscopic Particle Image Velocimetry (SPIV) system was assessed in a towing tank. To estimate the systematic error and random error of mean velocity and turbulence properties measurement, velocity field of uniform flow was measured. Total uncertainty of the axial component of mean velocity was 1.45% of the uniform flow speed and total uncertainty of turbulence properties was 3.03%. Besides, variation of particle displacement was applied to identify the change of error distribution. In results for variation of particle displacement, the error rapidly increases with particle movement under one pixel. In addition, a nominal wake of a model ship was measured and compared with existing experimental data by five-hole Pitot tubes, Pitot-static tube, and hot wire anemometer. For mean velocity, small local vortex was identified with high spatial resolution of SPIV, but has serious disagreement in local maxima of turbulence properties due to limited sampling rate.

• Journal of Mechanical Science and Technology
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• v.15 no.4
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• pp.500-509
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• 2001

Offshore subsea pipelines must be stable against external loadings, which are mostly due to waves and currents. To determine the stability of a subsea pipeline on the seabed, the Morrison equation has been applied with prediction of inertia and drag forces. When the pipeline is placed in a trench, the force acting on it is reduced considerably. Therefore, to consider the stability of a pipeline in a trench, one must employ reduction factors. To investigate the stability of various trenches, we numerically simulated flows over various trenches and compared them with experimental data from PIV (Particle Image Velocimetry) measurements. The present results were produced ar Reynolds numbers ranging from 6$\times$10$^3$to 3$\times$10(sub)5 based on the diameter of the cylinder. Quasi-periodic flow patterns computed by large-eddy simulation were compared with experimental data in terms of mean flow characteristics fro typical trench configurations (W/H=1 and H/D=3, 4). The stability for various trench conditions was addressed in terms of mean amplitudes of oscillating lift and drag, and the reduction factor for each case was suggested for pipeline design.