• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2007년도 추계학술대회
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• pp.63-65
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• 2007

The paper reports on a new type of combinatorial chaotic and serpentine micromixer. Such a new and novel micromixer is simple to fabricate and easy to use. The micromixer is characterized and visualized with the help of the Micro-LIF technique. The new micromixer will e further applied to lab-on-chip device. The mixing capabilities of this mixer is about 30-33%.

• 한국가시화정보학회지
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• 제15권1호
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• pp.25-31
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• 2017

This study aims to visualize the Marangoni flow inside a droplet placed on heated hydrophobic surface and to measure its internal velocity field. The experimental result shows that the internal velocity increases with the increase of the plate temperature. In addition, the temperature difference induces the initial flow and drives the Marangoni circulation inside the droplet as soon as the evaporation starts (i.e. the thermal Marangoni flow). The fluorescence particles in the droplet trace two large-scale counter-rotating vortex pairs yielding the downwards flow along the vertical central axis. These vortex pairs gradually become small and move towards the contact line as time goes by, and this Marangoni flow sustains only for a half of the total evaporation time.

• 한국가시화정보학회지
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• 제2권2호
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• pp.3-7
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• 2004

In this paper, computational aeroacoustics (CAA) method is used for flow-noise analysis and flow-noise visualization. High order high resolution scheme of optimized high order compact is used to resolve the small acoustic quantities and large flow quantities at the same time. An adaptive nonlinear artificial dissipation model and generalized characteristic boundary condition are also used. Aeolion tone noise, cavity noise, and jet noise are investigated. The visualizations of flow-noise are successful and characteristics of noise are studied. It is observed that the propagation directivity of noise is different with that of flow. With the help of CAA method, the visualization of noise is possible.

• 한국가시화정보학회지
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• 제2권2호
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• pp.58-65
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• 2004

The purpose of this visualization study is to investigate the effect of reduced frequency qualitatively by examining wake patterns for dragonfly flight motion. Dragonflies have two pairs of wing (a forewing and hindwing) and flight is achieved by a pitching and plunging, so it makes a separation over the wings. The separation affects the wake pattern and changed wake pattern has an influence on lift, drag, and propulsion. This experiment was conducted by using a smoke wire technique and a camera fixed above the test section used to take a photograph of the wake. An electronic device is mounted below the test section to find the exact mean positional angle of the wing. The reduced frequency in the experiment is 0.15, 0.3 and 0.45. Results show that reduced frequency is closely related to the wake pattern that determines flight efficiency.

• 한국가시화정보학회지
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• 제10권3호
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• pp.37-41
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• 2012

Plate-fin heat exchanger is a kind of compact heat exchangers with a good performance in heat transfer. It is widely used in various engineering fields such as aerospace, chemical and biomedical industries. Quantitative and qualitative flow visualization study were performed using the water model of commercial plate-fin heat exchanger with header angles of $30^{\circ}$. The Reynolds number was 100. Conventional digital particle image velocimetry was used to measure the instantaneous velocity fields of the header region and the flow visualization using dye injection and hydrogen bubble method were applied to capture the qualitative flow characteristics. The results showed the existence of separation flow region at the junction area and the bottom wall of the exit region.

• 한국가시화정보학회지
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• 제11권3호
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• pp.5-11
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• 2013

It is of great importance to obtain the uniform layer thickness in the multi-layer co-extrusion processes. In the present study, the three-dimensional numerical simulation was carried out using the open source code named OpenFOAM(R) to understand the flow characteristics in the multi-layer die. In this numerical study, Multi-thin-layers were successfully computed depending on the number of repeating units. The generation mechanism for the multi-layer was numerically verified by the flow simulation and visualization in the co-extrusion die using OpenFOAM(R). The results suggested that the multi-layer has a divided and folded mechanism similar to the stretching and folding in the chaotic flow.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 춘계학술대회 논문집
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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.

• 한국가시화정보학회지
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• 제13권1호
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• pp.26-29
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• 2015

A laboratory experiment was carried out to observe and visualize ventilated supercavitation phenomena around a moving underwater body which is attached to a newly designed high-speed (Max. 20 m/s) carriage system in a wave tank. Compared to the existing many other experimental studies using cavitation tunnels, where the body is at rest and the fluid is in motion in a bounded or closed environment, the present experimental study deals with super-cavity formation in unbounded or free-surface bounded environments, where the body is in motion and the fluid is at rest. Main attention is paid to the effective visualization of the steady-state cavity formations around a moving body and, those cavity formations are reported pictorially according to the body speed, ventilated air-pressure, and with or without a cavitator.

• 한국가시화정보학회지
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• 제11권1호
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• pp.34-40
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• 2013

Gas/liquid two-phase ejector is a device without moving parts, in which liquid is used to drive gas of a low-pressure source. In this paper, the hydrodynamic characteristics of a vertical down type two-phase ejector were studied using an air-water loop system. Entrained air flow rates were measured with inlet and outlet pressures of the ejector with varying water flow rate. Homogeneous bubbly flows in the discharge pipe were confirmed by the high speed flow visualization method. Quantitative measurements of void fraction were made using a newly developed fiber optic probe system.

• 한국가시화정보학회지
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• 제4권2호
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• pp.3-5
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• 2006

Recently, the next-generation advanced flow visualization techniques such as holographic PIV, aynni.c PIV, echo-PIV, micro/nano-PIV, and X-ray PIV have been introduced. These advanced mea-surement techniques have a big potential as the core technology for analyzing outmost thermo-fluid flows in future. They would be indispensable in solving complicated thermo-fluid flow problems not only in industrial fields such as automotive, space, electronics, aero- and hydro-dynamics. steel, and information engineering, but also in the research fields of medical science, bio-medical engineering, environmental and energy technology etc. Especially, NT (Nano Technology) and BT (Bio Technology) strongly demand these advanced measurement techniques, because it is impossible for conventional measurement methods to observe the nano- and bio-fluidic flow phenomena. In this article, the basic principle of these high-tech flow visualization techniques and their practical applications which cannot be resolved by conventional methods, such as blood flows in a micro-tube, in vivo analysis of micro-circulation, and flow around a living body are introduced as a blue ocean strategy.