• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2005년도 추계학술대회 논문집
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• pp.50-53
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• 2005

The turbulent flow around a sphere was investigated in a streamwise meridian plane using two experimental techniques: smoke-wire flow visualization in wind tunnel at Re=5,300 and PIV measurements in a circulating water channel at Re=7,400. The smoke-wire visualization shows flow separation points near an azimuthal angle of $90^{\circ}$, recirculating flow, transition from laminar to turbulent shear layer, evolving vortex roll-up and fully turbulent eddies in the sphere wake. In addition, the mean flow pattern extracted by particle tracing method in water tunnel at Re= 14,500 reveals two distinct comparable toroidal(not closed) vortices in the recirculation region. The mean velocity field measured using a PIV technique demonstrates the detailed wake configuration of close symmetric recirculation and near-wake configuration with two toroidal vortices, reversed velocity zone and vorticity contours.

• 한국화재소방학회논문지
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• 제15권1호
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• pp.41-46
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• 2001

수평 평판과 충돌하는 제트에 의해 생성되는 연기유동을 관찰하기 위해 질소가스네 kerosene 연기입자를 띄워 유동장을 가시화하였다. 광원으로는 아르곤-이온 레이져 평면광이 사용되었다. Kerosene smoke의 산란 광에 의한 수직평면 상(image)과 수평평면 상을 고속 CCD 카메라와 비디오 카메라로 녹화하였으며, 얻어진 영상으로부터 연기선단의 순간속도 및 평균속도를 측정하였다.

• 한국가시화정보학회지
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• 제8권3호
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• pp.12-21
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• 2010

Swirling flows are found in very wide range of applications, for examples, cyclone separators, spraying machines, heat exchangers and jet pumps, ect. Relatively, little work has been done on the swirl flow using flow visualization techniques. This study deals with many visualization techniques to study on swirling flow. These techniques are related to oil films methods, smoke, dye liquids, liquid crystal, stroboscope light, smoke wire, white light, naphthalene sublimation, LDV(lase doppler Velocimetry) and PIV(particle image velocimetry). The present work has handled single, annular, carved tube, swirl expansion and swirl wake using several visualization methods in the vertical and horizontal circular tube.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.401-402
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• 2006

The turbulent flow around a sphere was investigated using two experimental techniques: smoke-wire flow visualization in wind tunnel at Re=5300, 11000 and PIV measurements in a circulating water channel. The smoke-wire visualization shows flow separation points near an azimuthal angle of $90^{\circ}$, recirculating flow, transition from laminar to turbulent shear layer, evolving vortex roll-up and fully turbulent eddies in the sphere wake. The mean velocity field measured using a PIV technique in x-y center plane demonstrates the detailed near-wake structure such as nearly symmetric recirculation region, two toroidal vortices, laminar separation, transition and turbulent eddies. The PIV measurements of turbulent wake in y-z planes show that a recirculating vortex pair dominates the near-wake region.

• 한국항공우주학회지
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• 제44권12호
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• pp.1017-1026
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• 2016

두 가지의 비표면 가시화 기법과 이들 기법의 와류 적용 예를 기술한다. 두 가지 가시화 기법 중 하나는 전통적인 연기선 기법이고, 또 다른 하나는 가정용 초음파 가습기에서 발생하는 미세 수적을 사용하는 기법이다. 연기선 기법은 공기 흐름 속도에 제한이 있으며(0.07 mm 지름의 연기선의 경우 약 5 m/sec), 오염의 문제점이 있지만 매우 정교하고 선명한 연기 유맥선 시트를 발생시킬 수 있다. 이 기법은 3차원 날개의 날개 끝 와류의 가시화에 적용되었다. 초음파 가습기 미세 수적 기법은 연기선 기법에 비하여 공기 흐름 속도를 보다 크게 할 수 있으며(10 m/sec 이상), 독성과 오염의 문제를 해결할 수 있다. 초음파 가습기 미세 수적 기법은 정점 스트레이크를 가지는 이중 삼각날개에서 발생하는 복잡한 와류 시스템의 가시화에 성공적으로 적용되었다.

• 대한기계학회논문집B
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• 제25권1호
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• pp.71-77
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• 2001

A flow visualization study using the oil film method and the smoke-laser light sheet arrangement is carried out to investigate the three-dimensional flow pattern around the free end surface region of a finite circular cylinder (aspect ratios of 1.25 and 4.25) mounted on a flat plate. The experiment is performed for the cases of two Reynolds numbers: 5.92${\times}$10$^3$and 1.48${\times}$10(sup)5. Various kinds of singular points on the free-end surface are disclosed from the oil surface flow visualization. The smoke-laser light sheet visualization, to aid in understanding the oil streak-line patterns, clearly demonstrates that a pair of tornado-like vortices marched along the downstream together with a pair of side tip vortices. A topological sketch to characterize the surface flow and the four vortices emanating from the top surface is included.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2005년도 추계학술대회 논문집
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• pp.64-68
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• 2005

In this study, the smoke flows of the inner subway station were visualized through a numerical analysis and visualization experiment in the subway fire. A transparent acrylic model was designed and installed as 1:25th scale-down as the actual subway station by using geometrical similarity The properties of subway fire were reconstructed according to Densimetric Froude Similarity. The 47 to 53 ratio of the mixed air and Helium was inputted in the inner acrylic model to describe 1MW fire intensity with reference to the experiment paper. For the same time, the fire smoke from a smoke generator was inputted in the inner acrylic model with the mixture. At this time, the buoyancy effect of Helium gas went up the smoke to the acrylic model. When the sheet beam of Ar-lon laser was given out to the top and stair of subway model, the digital camcorder took the images of the scattered cluster of smoke particles when applying the smoke management system and PSD.

• 한국추진공학회지
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• 제6권1호
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• pp.55-62
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• 2002

미세수적과 레이저 평면광을 사용하여 새로운 유동의 가시화 방법을 제안하였다. 미세수적은 약 5 내지 $10\mu\textrm{m}$ 크기로 가정용 초음파 가습기를 사용하여 생성시켰다. 조명은 3 W의 알곤 이온 레이저와 원통형 렌즈를 사용하여 레이저 평면광을 특정 와류장 단면에 형성시켰다. 이와 같은 새로운 유동의 가시화 방법을 측정부의 크기가 $0.9 m(W){\times}$0.9 m(H){\times}2.1 m(L)$$인 공군사관학교의 소형 풍동을 통하여 적용하였다. 가시화 결과를 통하여 미세수적을 이용한 새로운 가시화 방법이 풍동실험에 적용하기에 비교적 용이하며, 안전한 방법임을 보였다. 아울러 이 방법은 일반적으로 풍동실험에 적용되고 있는 스모크 가시화의 단점들을 보완함은 물론, 좀 더 높은 유동속도에서도 적용할 수 있었다.

• 한국가시화정보학회지
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• 제11권2호
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• pp.34-40
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• 2013

A flow visualization near submerged nozzle of solid rocket motor was conducted by experiments. A numerical simulation was also performed to reveal detailed phenomena. Radial cold flow simulating hot gas was introduced by a porous grain model which was manufactured by perforated steel plates. The grain model was mounted in high-pressure chamber which has quartz glass at the top of the grain model. From the high-speed images, a rotating vortex was observed and the two type of counter-rotating momentums were generated in numerical results. The rotating momentum was generated at the fin-slot grain because of unbalance between high-velocity flow from slots and low-velocity flow from fin-bases. As a result, roll torques can be produced by the rotating vortex tube.

• 한국가시화정보학회지
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• 제8권2호
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• pp.16-22
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• 2010

A flow visualization has been conducted to investigate unsteady flight characteristics of a model of dragonfly. The mechanism of lift generation by flapping wings is analyzed using smoke-wire and high speed camera. The experimental results of flow visualization show a discernible sequential dynamics that three mechanisms and high incidence angle of the wings are responsible for the lift generation. The leading edge vortex by the rapid acceleration of leading edge of the wing during initial stage of stroke causes a strong lift enhancement. Delayed stall during the stroke, fast supination and pronation of the wing near the end of each stroke are also responsible for the lift generation.