• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.149-156
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• 1999

In this study, aerodynmaic characteristics of the notch-back and fast-backpassenger vehicle models(1/10~1/12 acale) attached with winglets were experimentally investigated in a low speed wind tunnel. For various positions(X/L). tilted angles($\beta$) of a winglet, the aerodynamic forces on the vehicle model and rear-surface pressures were measured at various flow speeds. Also a flow of model surface was visualized by tuft method. The experimental results showed that winglets effect aerodynamic characteristics of vehicle models. A maximum of 3% reduction in lift coefficient was achieved with winglets at $\alpha$=-30$^{\circ}$. A maximum of 10% reduction in drag coefficient was achieved for a model with winglets and a rear-spoiler.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.610-613
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• 2016

항공기의 착륙 과정에서 지면효과에 의해 기체가 원하는 위치에 착지하지 못하는 경우가 있다. 이러한 현상들로 인해 항공기의 착륙 실패 또는 활주로 이탈로 인한 인명피해로 이어질 수 있다. 본 연구에서는 이러한 착륙과정에서 쓰이는 날개의 부품중 하나인 Spoiler에 대한 공력 해석을 EDISON 전산열유체 시스템을 이용하여 진행해 보았다. 특히 Spoiler의 전개 각도를 다양하게 변화시켜가며 그 전개 각도에 의한 Lift dumping effect에 초점을 맞추어 연구를 진행하였다. 예상과 동일하게 전개각도가 커질수록 양력은 감소하였으며 항력의 경우 선형적으로 증가하는 양상을 보였다. 또한 전개각도가 20도보다 커지는 구간부터는 양력이 음수로 작아지는 현상을 확인할 수 있었다.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.421-424
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• 2013

본 연구에서는 교육 및 연구를 위한 CFD 해석 프로그램인 EDISON_CFD를 이용하여 자동차 Spoiler의 장착 유무에 따른 공력 특성을 분석해보았다. Spoiler가 장착되지 않은 자동차의 공력 특성을 확인하고, Spoiler의 길이에 따라 공력 특성이 어떻게 차이가 나는지 비교하였다. HONDA S2000 차량의 압력 계수를 구하였고, 자동차 길이의 3.5%, 7%, 14%에 해당하는 길이의 Spoiler를 장착하여 어떠한 변화가 발생하는지 확인하였다. 그 결과 Spoiler의 길이가 길수록 짧을 때보다 상대적으로 좋은 효율을 보이는 것을 확인할 수 있었다.

• Proceeding of EDISON Challenge
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• 2016.11a
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• pp.23-26
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• 2016

Gurney Flap은 자동차의 스포일러 부분에 장착되는 고속주행용 Flap으로써 항공기에는 제한적으로 사용되고 있다. 매우 짧게 설치되는 특성이 있기 때문에 Flap의 길이를 항공기의 기준으로 10%로 증가시켜 Flap으로써의 역할을 확인해 보고자 실험을 진행하였다. Gurney Flap을 장착한 형상 3가지 모두 기본형의 NACA0012형상보다는 양력과 항력이 모두 증가하는 형상을 보였다. 양항비의 경우는 항력의 증가로 인해서 NACA0012에 비해서 모두 감소하는 것으로 나타났다. Gurney Flap은 고양력장치로 사용하기에는 다소 무리가 있지만, Dogfight와 같이 고항력장치를 사용하는 경우에는 좋은 성능을 기대할 수 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.11a
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• pp.31-31
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• 2000

초음속 충돌제트(impinging jet)의 열 및 운동량 전달(heat and momentum transfer)은 로켓의 이ㆍ착륙, 다단 로켓의 분리, 로켓의 방향조절을 위해 배기 노즐에 부착되는 제트 베인(jet vane)이나 스포일러 탭(spoiler tab), 수직/단거리 이착륙기의 발진, 미사일 발사시스템, 전투기 동체, 날개, 후미 부분에서 발사되는 미사일의 배기가스가 주변장치 등에 충돌할 때 발생되는 문제점 등을 사전 예측하여 관련장비의 설계 둥에 유용한 자료로 이용된다. 따라서 이에 대한 기초 연구로서 초음속 유동 실험장치를 이용하여 마하수(Mach Number) 1.0 및 1.8인 경우에 대하여 수직/경사평판에서 팽창 비, 거리, 경사각에 따른 충돌 면에서의 단열 벽면온도를 측정하였다. (중략)

• The Journal of Korean Society for Radiation Therapy
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• v.17 no.1
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• pp.57-71
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• 2005

Purpose : To evaluate radiation dose and accuracy with TLD and diode detector when treat total skin with electron beam. Materials and Methods : Using Stanford Technique, we treated patient with Mycosis Fungoides. 6 MeV electron beam of LINAC was used and the SSD was 300 cm. Also, acrylic speller(0.8 cm) was used. The patient position was 6 types and the gantry angle was 64, 90 and $116^{\circ}$. The patient's skin dose and the output were detected 5 to 6 times with TLD and diode. Result : The deviations of dose detected with TLD from tumor dose were CA $+\;6\%$, thigh $+\;8\%$, umbilicus $+\;4\%$, calf $-\;8\%$, vertex $-\;74.4\%$, deep axillae $-\;10.2\%$, anus and testis $-\;87\%$, sole $-\;86\%$ and nails shielded with 4mm lead $+4\%$. The deviations of dose detected with diode were $-4.5\%{\sim}+5\%$ at the patient center and $-1.1\%{\sim}+1\%$ at the speller. Conclusion : The deviation of total skin dose was $+\;8\%{\sim}-\;8\%$ and that deviation was within the acceptable range(${\pm}\;10\%$). The boost dose was irradiated for the low dose areas(vertex, anus, sole). The electron beam output detected at the sootier was stable. It is thought that the deviation of dose at patient center detected with diode was induced by detection point and patient position.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.12
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• pp.1223-1229
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• 2007

Flow traveling over a cavity opening forms a vortex due to unstable shear layer and induces an aerodynamic pressure excitation from the diffusion of the vortex convecting out of the trailing edge of the opening. The interaction between the excitation force and the cavity response sustains resonance in the resonator(cavity) and locked-in vortex shedding at the leading edge of the opening. The aerodynamic excitation force can be described from the diffusion of the vortex over the trailing edge and the level of its diffusivity is related to the strength of vorticity seeded at the leading edge. In this study, the control scheme of the internal pressure oscillation was proposed from regulating the vorticity at the leading edge by use of an oscillating spoiler. It was found that the relative motion between the spoiler and the air mass at the cavity opening influenced vorticity strength and the control was achieved by direct feedback of the cavity pressure fluctuation to the actuator.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.196-199
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• 2005

Flow traveling over a cavity opening forms a vortex due to unstable shear layer and induces an aerodynamic pressure excitation from the diffusion of the vortex convecting out of the trailing edge of the opening. The interaction between the excitation force and the cavity response sustains resonance in the resonator(cavity) and locked-in vortex shedding at the leading edge of the opening. The aerodynamic excitation force can be described from the diffusion of the vortex over the trailing edge and the level of its diffusivity is related to the strength of vorticity seeded at the loading edge. In this study, the control scheme of the internal pressure oscillation was proposed from regulating the vorticity at the leading edge by use of an oscillating spoiler. It was found that the relative motion between the spoiler and the air mass at the cavity opening influenced vorticity strength and the control was achieved by direct feedback of the cavity pressure fluctuation to the actuator.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.610-615
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• 2016

Diverse accessories are used in automobiles, such as navigation systems, front and rear cameras, spoilers, and sun visors. Sun visors block sunlight so that drivers can drive safely with a better view, and they are used in many automobile designs. However, when large plastic products are manufactured using injection molding, there are many difficulties that develop, like weld lines, short shots, flow marks, imperfections, and distortion. In this study, a CAE simulation was conducted based on previous results to predict potential problems in the injection molding of large products. The flow characteristics up to complete charge for the melting resins were captured using a computer-aided engineering simulation. The temperature departure on the front part of a flow was about $10^{\circ}C$ and very stable. The practical ejecting time of the cold runner was about 70 seconds in the simulation. Finally, the capability of a suitable injection machine was calculated and recommended by prediction of the injection pressure and the die clamping force.

• Journal of Korean Society of Disaster and Security
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• v.11 no.2
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• pp.61-67
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• 2018

Scour protection methods can be categorized as two types: The first is to reduce the horseshoe and wake vortices which are the main reasons for local scour. Either small cylindrical structures or separated vertical deflectors can be placed in front of the pier or the horizontal deflector (or collar) can be attached to the pier like the spoiler to reduce the dynamics of vortical structures. The second is to employ the protection layer to keep the bed material in place, which is a common method with a merit of immediate effect by using block mat or tetrapod. This study examined the effect of scour reduction using the former method. The relationship between the reflector interval and reduction of scour was not clear. It is assumed that the width of the reflector is somewhat correlated with the reduction of the scour. As the KC numbers increases, the Effect of Scour reduction rate is shown to decrease. Also, Scour reduction rate showed a rapid change at $U_R=25$ or KC = 8.