• 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.

• 산업기술연구
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• 제19권
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• pp.59-65
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• 1999

This study is to analyze turbulent flow over a backward-facing step in a rectangular duct. The side wall effects on the internal flow were determined by varying the aspect ratio(defined as the step span-to-height ratio) from 1 to 20. In the flow behind a backward-facing step, separation, recirculation and redeveloping is occurred frequently. These phenomena appear in a particular variation by varying the aspect ratio. The results show that the aspect ratio has an influence on the velocity and reattachment length. When the AR is increased, the reattachment length is increased. For 6 over aspect ration, the rate of increase is decreased. The length of recirculation in the upper corner is increased, as the increase of aspect ration. It's width is not changed in the variation of aspect ration. The transverse, streamwise and spanwise velocities were decreased along the flow down stream of the step.

• 한국가시화정보학회지
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• 제4권2호
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• pp.81-87
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• 2006

In this paper, we present flow patterns around and performance of an air-flow separator by using the numerical analysis. With this separator, particles of different density are to be separated by using the drag force from the air flow. The low-density particles are designed to be separated by using inhalation through holes on a rotating drum. To obtain the flow informations needed for determining the proper design parameters, we have performed numerical simulations by using a commercial code, ANSYS CFX. Various parameter set was tested and it was found that depending on the design of drums there exist critical parameter set regarding the attachment of light particles on the drum, which is prerequisite for the separation of materials. We present here the possibility of using the present design in separation of particles mixed in the clod for use in recycling.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1998년도 제10회 학술강연회논문집
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• pp.15-15
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• 1998

The problem of the impingement of a sonic or a supersonic jet on a flat surface has not only wide applications but has also interesting and very complex flow phenomena. The main applications of this impinging jet include prediction of solid surface erosion, design of launcher systems, stage separation of multi-stage rocket system, V/STOL operations, thermal spray system, and manufacturing technologies of materials. Much have been learned about the supersonic impinging jet flow field but many fundamental questions have not been answered satisfactorily. The problem encompasses many facets of fluid dynamics which, in combination, present the compressibility effect and the viscous-inviscid interaction, coupled with flow separation and reattachment. What is more, there are many flow parameters that have on the impinging jet flow field, for example, Mach number, Reynolds number, pressure ratio, distance between the nozzle exit and flat plate, jet shock structure, nozzle diameter and etc. Thus the existing data on the supersonic impinging jet flow present considerable disagreement in which quantitative comparison between one result and another is often impossible.

• 한국군사과학기술학회지
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• 제8권3호
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• pp.116-123
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• 2005

An experimental investigation on the static and dynamic stall characteristics of elliptic airfoil was performed by PIV velocity field measurements. The flow Reynolds number was $3.13{\times}10^5$ and the reduced frequency of the pitch oscillation ranged from 0.075 to 0.125. The onset of static stall was caused by boundary layer separation which started at the trailing edge and progressed toward the leading edge. However, dynamic stall was caused by the vortex shed at the leading edge region and the flow field showed a vortex dominated flow with turbulent separation and alternate vortex shedding. The increase of reduced frequency increased the dynamic stall angle of attack and intensified the flow hysteresis in the down-stroke phase.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.527-528
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• 2012

플라즈마 유동제어를 통한 공기저항저감을 위해 DBD(Dielectric Barrier Discharge) 플라즈마 구동기를 설계하였고, 2D 시험모델의 풍동시험을 통해 항력저감을 측정하였다. 풍속이 없는 경우에는 유동박리 및 표면마찰저항이 존재하지 않으므로 플라즈마 유동제어를 통한 항력저감도 없었다. 2m/s의 풍속에서 유동박리제어를 통해 항력이 9.7%까지 감소됨을 확인하였으며, 풍속이 증가할수록 항력저감은 감소하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제25권2호
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• pp.365-374
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• 2001

Its a tendency to strengthen related international was as the importance on marine oil pollution recently becomes the issue. According to the regulation of IMO, oil discharge from ships is allowed under 15PPM only and oil filtering equipment is essential. Oily water separator of laminated plate type which is one of gravity type separator can be use as assistant equipment for the oil filtering system to meet the present IMO standard, because it fits well to process large amount of rich oil with high specific gravity. The purpose of this paper is to investigate an efficiency of oil/water separation with the characteristics of laminated plate arrangement. The analyse of oil contents for oil-water mixture were carried out in order to find an efficiency of oil/water separation and an experimental study was simultaneously carried out to investigate internal flow characteristics of separator by visualization method and PIV(Particle Image Velocimetry) measurement at three spaces of plates for 5, 10 and 15 mm with variation of inlet flow rates of $0.25m^3$/h and $0.5m^3$/h. The experimental results showed that the space of the plates acts a significant role in the separating process.

• 한국막학회:학술대회논문집
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• 한국막학회 2002년도 춘계 총회 및 학술발표회
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• pp.123-125
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• 2002

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2006년도 추계학술발표회
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• pp.65-69
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• 2006

물제트분사장치가 부착된 NACA-0021 익 주변의 흐름을 업자영상유속계를 이용하여 고찰하였다. $R_e=6.0261\times10^4$에서 영각 (a) 을 $0^{\circ}\sim35^{\circ}$로 변화시켜가며, 물제트분사 속도를 0[m/s], 9.2[m/s] 의 2 가지로 조절한 결과 익 후류영역에서는 박리 후 비정상적인 (unsteady) 재순환 재부착 영역이 형성되었으며, 박리영역의 폭이 콴다 효과 (Coanda effect)를 갖는 물제트분사로 인하여 최대 1/3만큼 감소하는 경향을 확인하였다. 물분사가 없는 조건에서의 박리는 영각(a) $17^{\circ}\sim18^{\circ}$부근에서 시작되는 것이 관측되었으나, 물제트분사를 시켰을 경우 $20^{\circ}\sim21^{\circ}$에서 박리가 시작되는 것을 유통관측을 통해 알 수 있었다. 유통계측을 통해 익의 후연부 (trailing edge) 에서 생성되었던 와 (vortex, eddy) 가 물제트분사로 인해 소멸되는 것을 알 수 있었고, 영각이 작고 물분사 유속이 빠를 수록 박리영역의 감소가 더욱 가속화됨을 알 수 있었다.

• 대한의용생체공학회:의공학회지
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• 제43권3호
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• pp.170-176
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• 2022

Cell separation from a heterogenous mixture sample is an essential process for downstream analysis in biological, chemical, and clinical applications. This study demonstrates an integrated hybrid device of the viscoelastic focusing in a straight rectangular channel and subsequent size-based separation using acoustophoresis to attain high efficiency and separation tunability. For particle pre-alignment in a viscoelastic fluid, the flow rate higher than 10 μl/min was required. Surface acoustic wave-based lateral migration of particles with different sizes (13 and 27 ㎛) was examined at various applied voltages and flow rate conditions. Therefore, the flow rate of 100 μl/min and the applied voltage of 20 V_pp can be used for size-based particle separation.