• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1051-1056
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• 2006

The mean and RMS velocity field of the respiratory gas flow in the human airway was studied experimentally by particle image velocimetry (PIV). Some researchers investigated the airflow for the mouth breathing case both experimentally and numerically. But it is very rare to investigate the airflow of nose breathing in a whole airway due to its geometric complexity. We established the procedure to create a transparent rectangular box containing a model of the human airway for PIV measurement by combination of the RP and the curing of clear silicone. We extend this to make a whole airway including nasal cavities, larynx, trachea, and 2 generations of bronchi. The CBC algorithm with window offset (64 $\times$ 64 to 32 $\times$ 32) is used for vector searching in PIV analysis. The phase averaged mean and RMS velocity distributions in Sagittal and coronal planes are obtained for 7 phases in a respiratory period. Some physiologic conjectures are obtained. The main stream went through the backside of larynx and trachea in inspiration and the frontal side in expiration. There exist vortical motions in inspiration, but no prominent one in expiration.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.420-425
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• 2006

Measurements results of flow-structure-interactions (FSI) of an air-lifted body are introduced. An adaptive stereoscopic-PIV system has been constructed for the measurements of the air-lifted body. The measurement system consists of two cameras and optical sensors. The flow characteristics around a lifted cylinder body(length=60mmm, diameter =10mm, polystyrene) in the swirling flow field in a vertical pipe (length=600mm, inner diameter=) are investigated by the use of the constructed adaptive stereoscopic-PIV system. The images of the two cameras were used for the analysis of the flow fields around the floated cylinder body. The images of the cylinder body captured by the two cameras were used for the analyses of its motions. Four optical sensors (LED) were used for the detection of the postures of the freely-lifted cylinder body. The FSI analyses have been carried out to find the physical conditions at which the floating body is stabilized with its upright postures.

• Journal of the Korean Society of Visualization
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• v.17 no.2
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• pp.48-57
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• 2019

A straightforward strategy for particle image velocimetry (PIV) interrogation and post-processing has been proposed, aiming at reducing errors and clarifying vortex structures. The interrogation window size should be kept small to reduce bias error and improve spatial resolution. A spatial filter is then applied to the velocity field to reduce random error and clarify flow structure. The performance of three popular spatial filters were assessed: box filter, median filter, and local quadratic polynomial regression filter. In order to quantify random uncertainty, the image matching (IM) method is applied to an experimental dataset of homogeneous and isotropic turbulence (HIT) obtained by 2D-PIV. We statistically analyze the uncertainty propagation through the spatial filters, and verify the reduction in random uncertainty. Moreover, we illustrate that the spatial filters help clarify vortex structures using vortex identification criteria. As a result, PIV random uncertainty was reduced and the vortex structures became clearer by spatial filtering.

• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1699-1710
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• 2001

The characteristics of methanol and methanol blended (M85) sprays were investigated under atmospheric conditions at various temperature, ranging from on-vaporizing to vaporizing ambient conditions (298∼353 K). From laser scattering images, the macroscopic characteristics of the spray, such as the spray tip penetration and the spray angle, were determined. Entropy concept was introduced to represent homogeneity and PIV analysis was adopted to determine the fluid dynamic information at each location of the spray. The correlation between entropy and vorticity strength enabled us to find their relations. The effect of ambient composition, mainly of viscous effect as affected by CO$_2$levels, was investigated using PIV and entropy analysis. Spray width and entropy value were found to tend to decrease at increased CO$_2$levels.

• Journal of Korea Water Resources Association
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• v.38 no.10 s.159
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• pp.851-859
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• 2005

Normalized cross-correlation (correlation coefficient) is a useful measure for pattern matching in PIV (Particle Image Velocimetry) analysis. Because it does not have a corresponding simple expression in frequency domain, several fast but inexact measures have been used. Among them, three measures of correlation for PIV analysis and the normalized cross-correlation were evaluated with a sample calculation. The test revealed that all other proposed correlation measures sometimes show inaccurate results, except the normalized cross-correlation. However, correlation coefficient method has a weakpoint that it requires so long time for calculation. To overcome this shortcoming, a fast and exact method for calculating normalized cross-correlation is suggested. It adopts Fast Fourier Transform (FFT) for calculation of covariance and the successive-summing method for the denominator of correlation coefficient. The new algorithm showed that it is really fast and exact in calculating correlation coefficient.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.566-569
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• 2001

Researchers have invectigated nasal flow both numerically and experimentally for centuries. Experimental studies most have suffered from various limitations necessary to allow the measurements to be obtained with available equipment. Nasal airflow can be subdivided into two interrelated categories; nasal airflow resistance and heat and mass transfer between the air stream and the walls of the nasal cavity. In this study, thanks to a new method for model casting by a combination of Rapid prototyping and Solidification of clear silicone, a transparent rectangular box containing the complex nasal cavity is made for PIV experiments. The CBC PIV algorithm is used for analysis.

• 한국가시화정보학회:학술대회논문집
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• 2005.12a
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• pp.40-45
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• 2005

Velocity and density distributions of a high-speed and initial $CO_{2}$ jet flow have been analyzed simultaneously by a developed three-dimensional digital speckle tomography and a particle image velocimetry(PIV). Three high-speed cameras have been used for tomography and PIV since a shape of a nozzle for the jet flow is asymmetric and the initial flow is fast and unsteady, The speckle movements between no flow and $CO_{2}$ jet flow have been obtained by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays for density gradients. The three-dimensional density fields for the high-speed $CO_{2}$ jet flow have been reconstructed from the deflection angles by a real-time tomography method and the two-dimensional velocity fields have been calculated by a PIV method simultaneously and instantaneously.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.6
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• pp.1195-1202
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• 2001

The flow characteristics in a bifurcated duct are investigated experimentally. Physical properties such as mean velocity vectors, mean x-y stress distributions, mean vorticity and total pressure distributions are Obtained for three different Reynolds numbers(578, 620, 688) Using PIV measurements and CFD analysis. Also, three different rates of discharge Q=26.11 l/min, Q=28.11 $\ell$/min, Q=31.17 $\ell$/min) were selected foy experimental conditions. The results of this study would be useful to the engineer in designing the flow systems for heating, ventilation, air conditioning and wastewater purification plants.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.515-516
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• 2006

Internal and inlet flows of a cross-flow fan have been visualized using a particle image velocimetry(PIV) to analyze a relationship with a performance of a room air conditioner(RAC). A test model which has a geometric similarity with the real RAC has been manufactured for the experiment and the flow characteristics have been analyzed with various flow rates and inlet grill angles for the cross-flow fan. The experimental results using the PIV technique have been compared with the existing numerical results. Also, a location and movement of an eccentric vortex which can affect the performance and noise of the RAC has been investigated by the PIV with various flow rates and inlet grill angles.

• 한국가시화정보학회:학술대회논문집
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• 2004.11a
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• pp.102-103
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• 2004

Simultaneous CH and OH planar laser induced fluorescence(PLIF) and stereoscopic particle image velocimetry(PIV) measurements have been developed to investigate the local flame structure of turbulent premixed flames. The developed simultaneous two radical concentrations and three component velocity measurements on a two-dimensional plane was applied for relatively high Renolds number turbulent premixed flames in a swirl stabilized combustor. All measurements were conducted for methane-air premixed flames in the corrugated flamelets regime. Strong three-dimensional fluctuation implies that misunderstanding of the flame/turbulent interactions would be caused by the analysis of two-component velocity distribution in a cross section. Furthermore, comparisons of CH-OH PLIF and three-component velocity field show that the burned gases not always have high-speed velocity in relatively high Renolds number turbulent premixed flame.