• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.795-798
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• 2002

This paper dispicts the vortical flow characteristics over a delta wing using a computational analysis for the purpose of investigating and visualizing the effect of the angle of attack and fee stream velocity on the low-speed delta wing aerodynamics. Computations are applied to the full, 3-dimensional, compressible, Navier-Stokes Equations. In computations, the free stream velocity is changed between 20m/s and 60m/s and the angle of attack of the delta wing is changed between $16^{\circ}\;and\;28^{\circ}$. For the correct prediction of the major features associated with the delta wing vortex flows, various turbulence models are tested. The standard $k-{\varepsilon}$ turbulence model predict well the vertical flows over the delta wing. Computational results are compared with the previous experimental ones. It is found that the present CFD results predict the vortical flow characteristics over the delta wing, and with an increase in the free steam velocity, the leading edge vortex moves outboard and its streangth is increased.

• International Journal of Aeronautical and Space Sciences
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• 제4권1호
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• pp.63-74
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• 2003

The vortical flow of a 65-deg flat plate delta wing with a leading edge extension(LEX) was examined through off-surface visualization, 5-hole probe and hot-film measurements. The off-surface flow visualization technique used micro water droplets generated by a home-style ultrasonic humidifier and a laser beam sheet. The angles of attack ranged from 10 to 30 degrees, and the sideslip angles ranged from 0 to -15 degrees. The Reynolds number was $1.82{\times}10^5$ for the flow visualization, and $1.76{\times}10^6$ for the 5-hole probe and hot-film measurements. The comparison of the visualization photos and the flow field measurement showed that the two results were in a good agreement for the relative position and the structure of the wing and LEX vortices, even though the flow Reynolds numbers of the two results were much different. The wing vortex and the LEX vortex coil each other while maintaining a comparable strength and identity at zero sideslip. Neither a looping of the wing vortex around the strake vortex, nor the lopsided coiling of the stronger strake and the weaker wing vortices was observed. At non-zero sideslip, the downward movement of the LEX vortex when going downstream was enhanced on the windward side, and the downward and inboard movement of the LEX vortex when going downstream was suppressed on the leeward side. The counterclockwise coiling of the wing and LEX vortices was decreased significantly on the leeward side.

• 한국군사과학기술학회지
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• 제5권2호
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• pp.83-90
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• 2002

An experimental study was conducted to investigate the effects of a leading edge extension(LEX) on the vortex flow field over a delta wing by measuring the total pressure distribution in a subsonic wind tunnel. Freestream velocity was 40m/sec and Reynolds number per meter was $1.76{\times}10^6$. The wing with the LEX experienced a strong interaction between the LEX and wing vortices. As the angle of attack increased, the coupled vortex field of these two vortices maintained its strength and concentricity much better than the vortex field over the wing without the LEX.

• 한국항공우주학회지
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• 제34권10호
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• pp.7-15
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• 2006

스트레이크를 부착한 이중 삼각 날개에서 스트레이크의 붙임각이 날개면 압력분포와 와류 특성에 미치는 영향을 실험적으로 연구하였다. 스트레이크 붙임각의 음(-)방향 증가(스트레이크가 주 날개 윗면으로부터 pitch-down방향으로 부착된 상태)는 날개 전체의 받음각을 증가시키는 것과 같은 효과를 가져와 날개 윗면의 부압의 크기를 증가시켰다. 이러한 스트레이크 붙임각 변화에 의한 날개 윗면 부압 분포 변화는 와류의 강도 변화에 기인하기 보다는 와류 중심이 날개면에 가까이 위치하는 것에 기인하였다.

• 융복합기술연구소 논문집
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• 제6권2호
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• pp.21-24
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• 2016

Accurate simulation of wakeshapes behind a wing is important for the performance prediction of the aircraft and the wake hazard problem in the airport. In the present study, wakeshapes behind a wing inside tunnels are simulated in regard to the development of wing-in-ground effect vehicles. A discrete vortex method with a nonplanar ground modelling is used for the simulation. It was found that the wingtip vortices move toward outboard directions when the wing is in ground effect. When the wing is placed inside tunnels, the wingtip vortices move along the tunnel wall with counter clockwise direction. As the gap between the wingtip and the tunnel decreases, the wingtip vortices move further along the tunnel wall. Both vortices from bothsides of the wing will murge, which will be studied in future using a viscous computation.

• 대한기계학회논문집B
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• 제23권11호
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• pp.1444-1452
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• 1999

The turbulence structure of e. tip vortex generated by e. fixed wing was investigated with the use of two-dimensional laser Doppler velocimetry. The velocity field, composed of circumferential end axial components, was measured on the vertical section to the vortex trail, located at 2C downstream from the wing tip in the incoming flow condition of $Re=2.24{\times}10^5$. A quasi 3-dimensional measurement technique by use of 2-dimensional LDV system was suggested for Reynolds stresses and the higher moments. The validity of this technique was confirmed with the uncertainty analysis. The budget of the turbulence kinetic energy was analyzed by those results in the radial direction of the vortex core. It is resulted that the production is to be very likely balanced with the dissipation in most range of the vortex core.

• Journal of Advanced Marine Engineering and Technology
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• 제25권5호
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• pp.1076-1085
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• 2001

Experimental investigations of the longitudinal vortices, which are produced by wing type vortex generators set up behind a circular cylinder in a rectangular channel, are presented. When the circular cylinder is set up in the rectangular channel, a horseshoe vortex is formed just upsteam of the circular cylinder. It generates a turbulent wake region behind the circular cylinder. Therefore, the region of the pressure loss behind the circular cylinder in increased and the size of the wake is small. These problems can be achieved by longitudinal vortices which are generated by wing-type vortex generator. In order to control the strength of longitudinal vortices, the angle of attack of the vortex generators is varied from 20 degree to 45, but the spacing between the vortex generators is fixed 6cm. The 3-dimensional mean velocity measurements are made using a five-hole probe. The vorticity field and streamwise velocity contour are obtained from the velocity field. The following results are obtained. Circulation strength is the maximum value when the angle of attack($\beta$) is $30^{\circ}$, and the vorticity field and streamwise velocity contour in case of $\beta$=$20^{\circ}$ show the trend similar to these in case of $\beta$=$30^{\circ}$, but do not in case of $\beta$=$45^{\circ}$.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.483-486
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• 2008

Numerical Simulation was performed to investigate the role of vortex generator. Vortex generator installed on the upper surface of the wing, generates vortex flow, mimic the external flow with boundary layer flow and transfer energy from outside to wall boundary. Vortex generator, thus, retards the flow separation and increases the lift and drag of the wing.

• 한국추진공학회지
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• 제8권4호
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• pp.43-54
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• 2004

본 가시화 연구는 잠자리 유형 모델의 위상차에 관한 후류의 변화를 관찰함으로써 위상차 효과를 정성적으로 조사하기 위해 수행되었다. 본 가시화 실험에 사용된 잠자리 유형 모델은 잠자리의 날개 형상을 모방한 앞뒤 날개를 가진 쌍으로 구성되어 있으며, 잠자리의 플래핑 날개를 확대하여 제작하였다. 본 연구는 smoke-wire 기법을 통한 가시화 실험이 수행되었고, 정확한 날개위치각도를 찾기 위하여 동기화 조정장치가 사용되었다. 이때 날개위치각도의 불확실성은 약 $\pm$$1^{\cire}$정도이며, 순간 날개 위치각도는 $-16.5^{\cire}$에서 $22.8^{\cire}$까지 변한다. 본 실험은 앞ㆍ뒤 날개의 위상차가 $0^{\cire}$, $90^{\cire}$, $180^{\cire}$, $270^{\cire}$인 경우 수행되었다. 본 연구 결과 위상차 $90^{\cire}$, $180^{\cire}$, $270^{\cire}$에서는 Karman Vortex가 발생되지만, 위상차 $0^{\cire}$에서는 Karman Vortex 현상이 관찰되지 않는다.

• 한국항공우주학회지
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• 제31권6호
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• pp.1-7
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• 2003

본 연구에서는 3차원 대칭형 날개의 정상/비정상상대에서의 공기력 특성을 Vortex 패널법을 이용하여 수치적으로 연구했다. 이 프로그램은 날개 표면에 분포된 x, y 방향에 따라 선형적으로 변화는 와(Vortex)를 이용하는 프로그램을 기반으로 하여 3차원 날개 주위의 비압축성 포텐셜 흐름에 적용하였고 박리와 후류의 변형은 고려하지 않았다. NACA Airfoil 자료와 비교한 계산결과는 매우 만족스러운 일치를 보여주었다. 또한 갑작스러운 pitch-up운동과 일정한 각속도로 피칭운동을 하는 비정상 날개에 대해서도 본 방법을 적용하였다. 비정상 상태의 연구에서는 출발와류의 생성과 시간에 따른 위치를 고려함으로서 출발와류가 날개의 공기력 특성에 미치는 영향을 계산하였다. 본 방법은 피칭이나 플래핑, 회전익 해석등의 더 복잡한 경우에도 적용되어질 수 있다.