• 한국가시화정보학회지
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• 제19권3호
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• pp.115-122
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• 2021

Oral cancer surgery typically consists of resection of lesion, neck dissection and reconstruction, and it has an impact on the position of hyoid bone. Therefore, morphological change of airway can occur since the geometric parameter of airway is correlated with the hyoid bone. Airflow is affected by geometry of the airway. In this study, flow characteristics were compared between pre- and post-surgery models by both particle image velocimetry (PIV) and numerical simulation. 3D model of upper airway was reconstructed based on CT data. Velocity is accelerated by the reduced channel area, and vortex and recirculation region are observed in pre- and post-surgery models. For the post-surgery model, high pressure distribution is developed by significantly decreased hydraulic diameter, and the longitudinal flow stream is also interrupted.

• 대한기계학회논문집B
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• 제28권8호
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• pp.961-967
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• 2004

An inclined jet impinging on a pin fin heat sink is proposed and investigated experimentally. To investigate the flow pattern, flow visualization using fluorescence and velocity measurement using particle image velocimetry(PIV) are conducted with water. The jet impinges over a wide span of the heat sink with a large recirculation in the upper free space and occasionally with another smaller one in the upstream corner. Further, thermal experimentation is conducted using air to obtain temperature profiles using a thermocouple rake in the air and using thermal image on the heat sink back plate, with impinging angles of 35, 45 and 55 degrees. The Reynolds number range based on the nozzle slot is varied from 1507 to 6405. The results show that impinging angle of 55 degree shows the largest heat transfer capability. The results of thermal experiment are compared and discussed with those of flow visualization.

• 한국가시화정보학회지
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• 제8권3호
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• pp.49-55
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• 2010

Thermal flows inside a laser printer are affected by generated heat from a fuser and boards. Thus, the effect of fans has been investigated to control the thermal flows and behaviors of toners. In order to analyze the phenomena experimentally, a PIV (Particle Image Velocimetry) has been used, and then the flow inside the printer has been predicted by the CFD (Computational Fluid Dynamics) in this study to determine the efficient flow distribution by an optimum design of the printer. The determined optimum design has been confirmed by the developed PIV technique so that the efficiency of the laser printer can be improved by the proposed design.

• 한국가시화정보학회지
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• 제1권2호
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• pp.52-57
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• 2003

The present paper investigated the effect of ultrasonic vibrations on the melting process of a phase-change material (PCM). The melting process in the square cavity with a heated vertical wall has been studied in terms of acoustic streaming. In the present study, applying with ultrasonic vibrations to the liquid were found to induce acoustic streaming which was clearly observed using by a particle image velocimetry (PIV) and a thermal infrared camera. The experimental results revealed that acoustic streaming could accelerate the melting process as much as 2.5 times, compared to the rate of natural melting (i. e., the melting without acoustic streaming). In addition, temperature and Nusselt numbers over time provided conclusive evidence of the important role of the acoustic streaming on the melting phenomena of the PCM.

• 한국가시화정보학회지
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• 제3권2호
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• pp.79-87
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• 2005

Two engines, one is conventional DOHC 4 valve and the other is narrow valve angle, were used to compare the characteristics of swirl motion generation in the cylinder. One intake port is deactivated to induce swirl flow. A PIV (Particle Image Velocimetry) was applied to measure in-cylinder velocity field according to inlet valve angle during intake and compression stroke. The results show that the flow patterns of narrow valve engine are much more stable and well arranged compared with the normal engine over the entire intake and compression stroke except early intake stage, and very strong swirl motion is generated at the end of compression stage in this engine nevertheless using straight port which is unfavorable for swirl generating. In the normal engine, however, strong swirl motion induced during intake stroke is destroyed as the compression progresses.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.87-95
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• 1995

A commercial DOHC four valve engine was modified to make a single-cylinder optical model engine with replaceable head. Three kinds of head were used to generate swirl, tumble, and combined swirl/tumble motion. Schlieren visualization technique was applied to characterize the in-cylinder flow qualitatively. Particle Image velocimetry has been developed and applied for the quantitative flow measurements. Axial and tangential flow motion inside the cylinder has been characterized. The swirl/tumble port shows beneficial results in terms of turbulence generation for the initial flame propagation and mean swirl motion for the overall flame propagation.

• 한국가시화정보학회지
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• 제17권1호
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• pp.53-59
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• 2019

Particle image velocimetry is performed in order to analyze flowfield induced by a dielectric barrier discharge plasma actuator. The velocity vector fields are obtained for the two different input voltage conditions; the voltage 3 and 5 kV at the frequency 10 kHz. The obtained flowfields show that the air is accelerated and its speed increase almost linearly over the covered electrode. The amount of momentum induced by the DBD plasma actuator is estimated from the obtained velocity fields, and the estimated values reasonably agree with the previous experiment.

• 한국가시화정보학회지
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• 제17권2호
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• pp.39-47
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• 2019

Impingement cooling utilizing synthetic jets is emerging as a popular cooling technique because of its high local cooling efficiency. The interaction between the vortex structure of the synthetic jet and the surface is crucial in understanding the mechanism of this technique. In this study, the impinging vortex structure and its advection are investigated by experiments with jet-to-surface spacing $2{\leq}H/D{\leq}7$, and synthetic jet Reynolds number $5120{\leq}Re{\leq}9050$. Using phase-locked particle image velocimetry, ensemble averaged (phase averaged) flow fields are obtained, and vortex identification and quantification techniques are applied. The shape, trajectory, and intensity change of the vortex are assessed. A sharp decline in the vortex intensity and the occurrence of a counter-rotating vortex at the impingement point are observed.

• 한국가시화정보학회지
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• 제19권2호
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• pp.32-40
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• 2021

Vapor-driven solutal Marangoni flow is governed by the concentration distribution of solutes on a liquid-gas interface. Typically, the flow structure is investigated by particle image velocimetry (PIV). However, to develop a theoretical model or to explain the working mechanism, the concentration distribution of solutes at the interface should be known. However, it is difficult to achieve the concentration profile theoretically and experimentally. In this paper, to find the concentration distribution of solutes around 2D droplet, the reverse tracking method with an artificial neural network based on PIV data was performed. Using the method, the concentration distribution of solutes around a 2D droplet was estimated for actual flow data from PIV experiment.

• 한국가시화정보학회지
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• 제20권1호
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• pp.29-37
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• 2022

We carried out a laboratory experiment about the thermo-fluidic characteristics of natural convection boundary layer over a vertical heated plate under constant heat flux condition. Particle image velocimetry has been applied to observe the surface convection velocity close to the vertical plate submerged in the water chamber with the condition of Ra = 7 × 10⁹ and Pr = 8.1. The velocity distributions indicate that the distinct stripe-like structures appears in the upstream (earlier transition region) and the distinct negative-positive and Λ(λ)-shaped flow structures in the downstream (mid-transition region). In addition, the temporal variation of spanwise and streamwise velocity is also presented.