• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.353-358
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• 2013

Present paper deals with turbulence-airfoil interaction noise and mainly investigates the effects of airfoil thickness on the broadband noise spectrum. The acoustic power radiation from an airfoil is predicted using high-order time-domain method, which is based on the computational aeroacoustic technique solving the linear Euler equations. The homogeneous and isotropic turbulence is generated by utilizing the synthetic turbulence modeling based on random particle method. The airfoils taken into consideration are a flat-plate and a NACA0012 airfoil aligned with uniform mean flow. The effects of airfoil thickness on the radiated inflow turbulence noise are investigated by comparing acoustic power spectrum predicted for each airfoil. The comparison of acoustic power spectrum reveals that the airfoil thickness significantly contributes the high frequency noise reduction.

• 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.

• 한국산학기술학회논문지
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• 제14권4호
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• pp.1533-1539
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• 2013

본 논문에서는 층류 및 난류 유동 특성 중 경계층 두께와 배제 두께, 그리고 모멘텀 두께에 대한 기존의 이론값과 실제 CFD 해석을 통한 수치해석의 데이터를 비교하였다. Freestream velocity는 Reynolds 수에 영향을 주게 되고, airfoil 주변에서의 유동의 층류 및 난류에 영향을 주게 된다. 층류 및 난류의 경우 유동특성이 달라 경계층 두께 및 배제두께, 그리고 모멘텀 두께가 달라지게 되고, 결국 airfoil의 공력특성인 양력과 항력, 그리고 pitching moment에 영향을 주며, separation point도 다양한 angle of attack에서 바뀌게 된다. 이번 연구에서의 목적은 비점성 유동과, 층류 및 난류 각 경우에 대한 유동특성에 대해 알아보는 것이다. 연구에서 사용된 airfoil의 경우 c=1인 Joukowski airfoil을 사용하였으며, CFD는 상용 프로그램인 Fluent 6.0을 통해 NACA-0012 airfoil을 사용하였다. 층류 및 난류에서의 $Re_c$는 $Re_c$=3,000, 700,000이며 각각에 해당하는 속도는 0.045, 10 m/s이다. 본 연구를 통해 기존의 실험값과 수치해석의 결과가 잘 일치함을 알 수 있으며, 이를 통해 다양한 airfoil의 형상을 모델링할 수 있는 근거를 마련하였다.

• 한국전산유체공학회지
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• 제17권4호
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• pp.93-102
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• 2012

Once the condensation of water vapor in moist air around a thin airfoil occurs, liquid droplets nucleate. The condensation process releases heat to the surrounding gaseous components of moist air and significantly affects their thermodynamic and flow properties. As a results, variations in the aerodynamic performance of airfoils can be found. In the present work, the effects of upstream Mach number and thickness ratio of airfoil on the transonic flow of moist air around a thin airfoil are investigated by numerical analysis. The results shows that a significant condensation occurs as the upstream Mach number is increased at the fixed thickness ratio of airfoil($\epsilon$=0.12) and as the thickness ratio of airfoil is increased at the fixed upstream Mach number($M_{\infty}$=0.80). The condensate mass fraction is also increased and dispersed widely around an airfoil as the upstream Mach number and thickness ratio of airfoil are increased. The position of shock wave for moist air flow move toward the leading edge of airfoil when it is compared with the position of shock wave for dry air.

• International Journal of Aerospace System Engineering
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• 제2권2호
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• pp.10-14
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• 2015

To design airfoils for novel airplanes, new knowledge of aerodynamics is required. In this study, modified Parametric SECtion (PARSEC) which is a airfoil representation is applied to airfoil design using a multi-objective genetic algorithm to obtain an optimal airfoil for consideration in the development of a Martian airplane. In this study, an airfoil that can obtain a sufficient lift and glide ratio under lower thrust is considered. The objective functions are to maximize maximum lift-to-drag ratio and to maximize the trailing edge thickness. In this way, information on the low Reynolds number airfoil could be extracted efficiently. The optimization results suggest that the airfoil with a sharper thickness at the leading edge and higher camber at the trailing edge is more suitable for a Martian airplane. In addition, several solutions which has thicker trailing edge thickness were found.

• 한국전산유체공학회지
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• 제19권4호
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• pp.75-79
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• 2014

In the paper, a study on the analysis of the effects of trailing edge thickness on the aerodynamic characteristics of an airfoil is described. In this research, modification of the formula representing NACA symmetric airfoil is studied to change the airfoil shape with different trailing edge thickness of user's choice. According to the result of aerodynamic characteristics, as the trailing edge thickness increases the maximum lift coefficient increases while the lift-to-drag ratio decreases. In this paper flow calculation results are demonstrated and the analysis on those results and findings on the effects of non-zero thickness of trailing edge are suggested.

• 산업기술연구
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• 제22권A호
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• pp.59-65
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• 2002

The objective of this study is to provide the quantitative and qualitative computational data about the aerodynamic performance of Gurney flap on NACA 00XX airfoils and to show the optimum Gurney flap height for each airfoil. The test was performed on 7 different airfoils from NACA 0006 to NACA0024, which have a 3% chord(=c) thickness interval. For every NACA 00XX airfoil, Gurney flap heights were changed by 0.5% or 0.25% chord interval from 0 to 2.0%c to study their effects. The aerodynamic characteristics of clean and Gurney flap airfoil were compared, and the influences of Gurney flap on each airfoil were compared. As a CFD (Computational Fluid Dynamics) solver, FLUENT, based on Navier-Stokes code, was used to calculate the flow field around the airfoil. The fully-turbulent results were obtained using the standard $k-{\varepsilon}$ two-equation turbulence model. The test results showed that Gurney flap increased the lift coefficient much more than the drag coefficient over a certain range of the lift coefficient, so the lift-to-drag ratio, which is the important index of airfoil performance, was increased. Based on the test results, the relationship between the airfoil thickness and the optimum Gurney flap heights was suggested.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.787-790
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• 2002

In this work, numerical experiments ave conducted to find out the optimal shape of flapping-airfoil using thickness variation airfoils. In the previous study of flapping-airfoil, we had found that the thrust efficiency of thicker airfoil is better than thinner one, but the latter has higher thrust coefficient. Therefore, we have combined thin(NACA0009) and thick(NACA0015)airfoil to overcome these demerits of each airfoil. Using this combined airfoil, we can achieve acceptable aerodynamic performances from thrust efficiency and coefficient points of view. In order to computational study, we have used parallel-implemented incompressible Wavier-Stokes solver. Computational results show how to design leading and trailing edge shapes.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.56.1-56.1
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• 2011

This study focus on the performance of blade with blunt airfoil which used at root region on Computational Fluid Dynamics(CFD). Based on the Phase VI had experiment by NREL, the experiment condition is also used for the performance of blade with the airfoil that trailing edge is changed. The thickness of airfoil trailing edge 1% and 5% is substituted for original airfoil. This study was progressing to calculate the pressure coefficient and torque from the effect on each airfoil according to difference of the thickness.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.362-365
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• 2007

In wind turbine blades, airfoils are required to have different spec when compared with airplane airfoil. Airfoils for wind turbine blade must have a high lift-to-drag ratio, moderate to high lift and especially low roughness sensitivity. Also an operation Re. No.s are lower than conventional airplane airfoils. At mid-span and inboard region, structural problems have to be considered. Especially, for stall regulated type, moderate stall behavior is essential part of design. For these reasons, airfoil design for HAWT blade is essential part of blade design. In this paper, root airfoil and tip airfoil are discussed. For a root region, 24% thickness airfoil is designed and for a top region, 12% thickness ratio is done. A inverse design method and panel method are used for rapid airfoil design. In this paper, a design method, features of airfoil shape and characteristics are discussed.