• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1017-1026
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• 2016

The present paper describes the two off-surface visualization techniques and their application examples to vortex flows. One of the two visualization techniques is the classical smoke-wire technique, and the other is the visualization technique using the micro water-droplets generated by the home-style ultrasonic humidifier. The smoke-wire technique has the limit of air flow speed (about 5 m/sec for 0.07 mm-diameter wire) and the pollution problem, but it produces very fine and clear streak line sheet. It is applied to visualize the wing-tip vortices of a 3-dimensional wing. The micro water-droplet technique has the larger limit of air flow speed (above 10 m/sec) and is free from pollution and toxic problems compared to the smoke-wire technique. It is successfully applied to visualize the complex vortex system of a double-delta wing with an apex strake.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.8
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• pp.1732-1739
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• 2004

In this paper, we proposed a visualization system with ANN algorithm that traits the motion of particles that move colliding in the water, where we got a great deal of variable information and predicts the distribution of particles according to the flowing of water and the pattern of their precipitation. We adopted ART2 to detect sensitively the collision between particles in this visualzation. Various particles and their mutual collision influencing the force such as buoyancy force, gravitational force, and the pattern of precipitation are considered in this system. Flowing particles whose motion is changed with the environment can be visualized in the system presented here as they are in real water.

• 한국항공운항학회:학술대회논문집
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• 2006.05a
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• pp.75-78
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• 2006

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.1-12
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• 2004

A flow visualization of the 1st cycle motion of a fling-clapping wing that might be employed by butterflies during flight is performed. In this numerical flow visualization, he time-dependent Navier-Stokes equations are solved for two wing motion types; 'fling followed by clap and pause' and 'clap followed by fling and pause'. The result is observed regarding the main flow features such as the sequential development of the two families of separation vortex pairs and their movement. For the fling followed by clap and pause motion, a strong separation vortex pair of counter-clockwise develops in the opening between the wings in the fling phase and they then move out from the opening in the following clap phase. For the clap followed by fling and pause motion, the separation vortex pair developed in the outside space in the clap phase move into the opening in the following fling phase. The separation vortex pair in the opening developed in the fling phase of the clap followed by fling and pause motion is observed to be stronger than that in the opening developed in the fling phase of the fling followed by clap and pause motion.

• 한국가시화정보학회:학술대회논문집
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• 2004.04a
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• pp.9-18
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• 2004

초음속 유동하에서 측추력기 주위의 유동 현상을 실험 및 수치해석을 이용하여 해석하였다. 실험은 버지니아공대의 초음속 풍동과 건국대의 초음속 풍동을 사용하였으며 계산 코드는 Aerosoft 사의 GASP(ver.4.0)과 건국대의 AADL3D를 사용하였다. 실험결과는 Schlieren, Shadow graph 등의 가시화 장치와 압력 센서와 PSP(Pressure Sensitive Paint)를 이용하여 유동장 특성과 압력분포를 구하여 실제 작용되는 힘과 모멘트를 구하였다. 실험조건은 자유류의 흐름이 마하수 4 이고 측추력기와 자유류의 압력비가 532 이었다. 성능향상 방안으로 측추력기 후방에 램프를 설치하는 것을 제안하였으며 이에 대한 실험을 수행하여 수직력에 대한 변화는 없지만 피칭다운 모멘트가 약 $70\%$ 감소함을 보여주어 실제로 성능이 향상되었음을 입증하였다. 또한 측추력기의 성능에 영향을 주는 여러 가지 인자들에 대한 가시화실험을 수행하여 그 이해를 돕고자 하였으며, 현재 건국대에서 보유하고 있는 고속유동 관련 실험장치의 소개와 이를 이용한 연구들을 소개하므로써 압축성 유동장 연구에 이러한 실험장치의 필요성에 대한 이해를 구하고자 한다.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.63-66
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• 2002

The Flow patterns around two cylinders in various arrangements were studied by a discrete vortex method. The flow for the surface of each cylinder was represented by arranging bound vortices at adequate intervals. The viscous diffusion of fluid was represented by the random walk method. The vortex distributions, streaklines, timelines and velocity vectors around two cylinders were calculated for centre-to-centre pitch rations of P/D=1.5 and 2.5, attack angles of $\alpha=0^{\circ},\;30^{\circ},\;60^{\circ},\;and\;90^{\circ}$, correspond to the photographs by flow visualization and the flow intereference between two cylinders in var ious arrangements was clearly visualized by a numerical simulation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1276-1293
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• 1993

A numerical and experimental flow visualization study of the louvered fin array, commonly used in a compact heat exchanger was performed. The flow structure which was obtained by using a finite difference method, was compared with an experimental result. The experimental flow visualization was performed by using a dye injection technique with 13:1 scale model. The effects of Reynolds number and fin geometries on flow structure and heat transfer were examined.

• Journal of the Korean Society of Visualization
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• v.1 no.2
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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.

• 한국가시화정보학회:학술대회논문집
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• 2007.11a
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• pp.51-54
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• 2007

The induced-charge electroosmosis (ICEO) is a kind of electroosmotic flow which is generated by the electrical charge induced by an externally-applied electric field. That kind of electrokinetic phenomenon provides a nonmechanical technique to handle microscale flows and particles. In this work, we report that the ICEO-like flow is observed around two kinds of circular-cylindrical rod submerged in a dielectric liquid. The conductivity of the solution is varied by adding a surfactant. The flow field is visualized by the PIV method, and average flow speed shows a remarkable dependence on electrical input frequency. Interestingly, the characteristics of the flow are quite different from the conventional ICEO with respect to the flow direction and the locations of center of vortices.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04b
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• pp.325-327
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• 2004

'생물정보학'이란 생물학적 데이터를 처리, 가공하여 정보를 얻어내는 연구 분야로 이 중 대사체학은 대사 경로 네트워크를 가시화하여 생명 활동을 이해하고자 하는 분야로, 대사 경로 내의 흐름을 한 눈에 알 수 있도록 가시화하여 보여 주는 도구가 반드시 필요하다 따라서 본 논문에서는 새로운 '대사 경로 드로잉 알고리즘'을 제안하였다. 대사 경로 그래프의 구조로는 이분 그래프를 이용하여 가독성을 높였으며. 이 그래프가 척도 없는(scale-free) 네트워크 구조라는 것과 구조적으로 환형, 계층적 선형 컴포넌트를 가진다는 것을 고려하여 사이즈가 큰 그래프도 적절하게 드로잉 하도록 하였다.