• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.199-205
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• 2006

Two dimensional turbulent flow simulations on the low Mach number - high Reynolds number flow about the NACA 4412 airfoil are carried out as the airfoil approaches a ground. It has been turned out that angle of attack between 2 and 8 is recommended for the airfoil to utilize the benefit of ground effect. For the large angle of attack, the increment of lift due to the ground effect is eliminated and negative aerodynamic effect such as destabilizing aspect in static longitudinal stability are occurred as the airfoil approaches a ground.

• 한국전산유체공학회지
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• 제11권4호
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• pp.81-89
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• 2006

Two dimensional turbulent flow simulations on the low Mach number - high Reynolds number flow about the NACA 4412 airfoil are carried out as the airfoil approaches a ground. It has turned out that angle of attack between 2 and 8 degrees is recommended for the airfoil to utilize the benefit of ground effect. For the large angle of attack, the increment of lift due to the ground effect is faded away and negative aerodynamic effect such as destabilizing aspect in static longitudinal stability occurs and the separation point moves to forward as the airfoil approaches a ground.

• EDISON SW 활용 경진대회 논문집
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• 제1회(2012년)
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• pp.81-84
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• 2012

항공기 설계에서 중요한 해석 대상중의 하나인 에어포일 NACA 4412 형상을 2차원 난류 점성유동으로 접근하여 일정 받음각에 따른 유동 현상을 실험 결과와 비교해 보았다. 또한, 역압력구배, 유동 박리, 와류 등의 현상이 어디에서 어떻게 생성되는지 해석을 통하여 분석해 보았다.

• 한국해양공학회지
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• 제21권3호
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• pp.16-25
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• 2007

A comparative study on the turbulent flaw simulation and the potential flaw analysis has been performed. A law Mach number preconditioned Navier-Stokes solver, using the multi-block grid method and a panel method based on the velocity potential, have been developed and validated by comparison to the experimental data. The present numerical analysis methods are applied to the ground effect problem around the NACA 4412 airfoil. It has been confirmed that the potential flaw analysis on the ground effect, using the image method, is consistent, to some degree, with the viscous calculations for high Reynolds number flows.

• 한국항공우주학회지
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• 제31권8호
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• pp.8-18
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• 2003

진동하는 에어포일의 근접후류에서의 레이놀즈수 효과를 조사하기 위한 실험적 연구가 수행되었다. NACA 4412에어포일은 1/4 시위 지점을 중심으로 조화적으로 피칭운동을 하고, 순간받음각은 +6$^{\circ}$에서 -6$^{\circ}$까지 진동되도록 하였다. 진동하는 에어포일의 근접후류에서의 난류강도를 측정하기 위하여 열선풍속계를 사용하였다. 본 연구에서 자유류의 속도는 3.4, 12.4, 26.2 m/s이다. 이러한 자유류 속도에 따른 시위 레이놀즈수는 $R_N=5.3{\times}10^4$, $1.9{\times}10^5$, $4.1{\times}10^5$이고, 무차원 진동수는 K=0.1이다. 레이놀즈수가 진동하는 에어포일의 근접후류에 미치는 영향을 나타내는 축방향 난류강도 분포를 제시하였다. 본 측정에서 모든 경우에 난류 강도는 $R_N=5.3{\times}10^4$인 경우에 아주 크고, $R_N=1.9{\times}10^5$과 $4.1{\times}10^5$인 경우에는 작다는 것을 관찰할 수 있었다. 진동하는 에어포일의 근접후류에서 레이놀즈수의 임계값은 층류분리인 경우, 분리가 발생하지 않거나 난류분리인 경우로 구분되며, 그 값은 $R_N=5.3{\times}10^4\;{\sim}\;1.9{\times}10^5$사이에 존재한다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제1권1호
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• pp.1-12
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• 2009

Wing-in-Ground vehicles and aerodynamically assisted boats take advantage of increased lift and reduced drag of wing sections in the ground proximity. At relatively low speeds or heavy payloads of these craft, a flap at the wing trailing-edge can be applied to boost the aerodynamic lift. The influence of a flap on the two-dimensional NACA 4412 airfoil in viscous ground-effect flow is numerically investigated in this study. The computational method consists of a steady-state, incompressible, finite volume method utilizing the Spalart-Allmaras turbulence model. Grid generation and solution of the Navier-Stokes equations are completed using computer program Fluent. The code is validated against published experimental and numerical results of unbounded flow with a flap, as well as ground-effect motion without a flap. Aerodynamic forces are calculated, and the effects of angle of attack, Reynolds number, ground height, and flap deflection are presented for a split and plain flap. Changes in the flow introduced with the flap addition are also discussed. Overall, the use of a flap on wings with small attack angles is found to be beneficial for small flap deflections up to 5% of the chord, where the contribution of lift augmentation exceeds the drag increase, yielding an augmented lift-to-drag ratio.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.568-572
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• 2000

A numerical investigation was performed to determine the effect of airfoil thickness on the optimum Gurney flap height using NACA 00XX series airfoils. Seven airfoils which have 3% chord thickness difference were used. These were NACA 0006, 0009, 0012, 0015, 0018, 0021, and 0024. A Navier-Stokes code, FLUENT, was used to calculate the flow field about airfoil. The fully turbulent results were obtained using the standard $k-{\varepsilon}$ two-equation turbulence model. To provide a check case fur our computational method, numerical studies for NACA 4412 airfoil were made and compared with already existing experimental data for this airfoil by Wadcock. For every NACA 00XX airfoil, Gurney flap heights ranging from 0.5% to 2.0% chord were changed by 0.5% chord interval and their effects were studied. With the numerical solutions, the relationship between $(L/D)_{max}$ and airfoil thickness as a function of flap height and the relationship between $(L/D)_{max}$ and flap height as a function of airfoil thickness were investigated. The same relationship for $(C_l)_{max}$ also were shown. From these results, the optimum flap size for each airfoil thickness can be determined and vice versa.

• 한국항공우주학회지
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• 제31권7호
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• pp.15-25
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• 2003

진동하는 에어포일의 근접후류 특성을 조사하기 위한 실험적 연구가 수행되었다. NACA 4412에어포일은 1/4 시위 지점을 중심으로 조화적으로 피칭운동을 하고, 순간받음각이 +6$^{\circ}$에서 -6$^{\circ}$까지 진동하도록 하였다. 진동하는 에어포일의 근접후류에서의 평균속도를 측정하기 위하여 열선풍속계를 사용하였다. 본 연구에서 자유류의 속도는 3.4, 12.4, 26.2 m/s이다. 이러한 자유류 속도에 따른 시위 레이놀즈수는 $R_N$=5.3${\times}10^4$, 1.9${\times}10^5$, 4.1${\times}10^5$이고, 무차원 진동수는 K=0.1이다. 레이놀즈수가 진동하는 에어포일의 근접후류에 미치는 영향을 나타내기 위하여 축방향 위상평균 속도분포를 제시하였다. 본 측정에서 모든 경우에 속도결손은 $R_N$=5.3${\times}10^4$인 경우에 아주 크고, $R_N$=1.9${\times}10^5$과 4.1${\times}10^5$인 경우에는 작다는 것을 관찰 할 수 있었다. 이와 같이 위상평균속도의 커다란 차이는 $R_N$=5.3${\times}10^4$과 1.9${\times}10^5$ 사이에 있다는 것을 관찰하였다. 따라서 본 연구는 진동하는 에어포일의 근접후류에서의 레이놀즈수의 임계값이 5.3${\times}10^4$에서 1.9${\times}10^5$ 범위에 존재한다는 것을 보여준다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.1014-1019
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• 2001

A numerical investigation was performed to determine the effect of airfoil on the optimum flap height using NACA 00XX and 44XX airfoils. The six flaps which have 0.5% chord height difference were selected. A Navier-Stokes code, FLUENT, was used to calculate the flow field of the airfoil. The code was first tested as a benchmark by modelling flow around a NACA 4412 airfoil. Predictions of local pressure coefficients are found to be in good agreement with the result of the experimental result. For every NACA 00XX and 44XX airfoil, flap heights ranging from 0.0% to 2.5% chord were changed by 0.5% chord interval and their effects were also studied. Representative results from each case are presented graphically and discussed. It is concluded that this initial approach gives an idea for the future development of the wind turbine optimum design.

• Journal of Advanced Marine Engineering and Technology
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• 제25권5호
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• pp.1091-1097
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• 2001

A numerical investigation was performed to determine the effect of airfoil on the optimum flap height using NACA 00XX and 44XX airfoils. The six flaps which have 0.5% chord height difference were selected . A Navier-Stokes code, FLUENT, was used to calculate the flow field of the airfoil. The code was first tested as a benchmark by modelling flow around a NACA 4412 airfoil. Predictions of local pressure coefficients are found to be in good agreement with the result of the experimental results. For every NACA 00XX and 44XX airfoil, flap heights ranging from 0.0% to 2.5% chord were changed by 0.5% chord interval and their effects were also studied. Representative results from each case are presented graphically and discussed. It is conclued that this initial approach gives an idea for the future development of the wind turbine optimum design.