• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.174-180
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• 1999

Aerodynamic characteristics of tandem airfoil under ground effect is investigated numerically. Some numerical results for NACA 6409 tandem airfoil are presented. The numerical results show that as being decreased distance between airfoils, the lift coefficient of leading airfoil is increased and that of trailing airfoil is decreased. Drag coefficient shows opposite property, At the same distance between leading airfoil and trailing airfoil, lower position of trailing airfoil give better tandem airfoil effect.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.512-515
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• 2009

This research describes on airfoil shape design, crucial to core technique and algorithm optimization for the wind turbine blade development. We grasped the parameter to define the airfoil shape in the wind turbine blade and aircraft, and the important performance characteristic of the airfoil. The airfoil shape function is selected by studying which is suitable for wind turbine blade airfoil development. The selected method is verified by to compare the generated airfoil shape with base airfoil. The new airfoils were created by the selecting shape function based on the well-known airfoil for wind turbine blades. In addition, we performed aerodynamic analysis about the generated airfoils by XFOIL and estimated the point of difference in the airfoil shape parameter using the aerodynamic performance results which is compared with basic airfoil. This result data applies to the fundamental research for a wind turbine blade optimization design and accomplished the aerodynamic analysis manual.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.27 no.1
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• pp.75-86
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• 2023

The angle of attack is highly sensitive to pitch point in the airfoil shape and the decline of pitch point value induces smaller angle of attack, which implies that airfoil profile possessing closer pitch point to the airfoil tip reacts more sensitively to upcoming wind. The method of conformal transformation functions is employed for airfoil profiles and airfoil surfaces are expressed with a trigonometric series form. Attack angle and ideal lift coefficient distributions are investigated for various airfoil profiles in wind turbine blade regarding conformal transformation and pitch point. The conformed angle function representing the surface angle of airfoil shape generates various attack angle distributions depending on the choice of surface angle function. Moreover, ideal attack angle and ideal lift coefficient are susceptible to the choice of airfoil profiles and uniform loading area. High ideal attack angle signifies high pliability to upcoming wind, and high ideal lift coefficient involves high possibility to generate larger electric energy. According to results obtained pitch point, airfoil shape, uniform loading area, and the conformed airfoil surface angle function are crucial factors in the determination of angle of attack.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.7
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• pp.581-585
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• 2007

Sonic arc airfoil derived from the TSD theory is modified to new airfoil shape and its aerodynamic performance in transonic flow is investigated. The numerical simulation using Euler equations for the modified sonic arc airfoil is performed. The numerical results are compared with the aerodynamic performance of NACA0012 airfoil, of supercritical airfoil, and of NACA64A210 airfoil. In the same free stream Mach number of transonic flow, the pressure drag of the modified sonic arc airfoil is smaller than that of NACA0012 airfoil and the lift-drag ratio of the modified sonic arc airfoil is much larger than that of NACA0012 airfoil. In the comparison of the drag-divergence Mach number of transonic flow, the drag-divergence Mach number of the modified sonic arc airfoil is larger than that of NACA64A210 airfoil but is smaller than that of supercritical airfoil.

• Proceedings of the KSME Conference
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• 2002.08a
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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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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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.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.3
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• pp.1-5
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• 2006

Birds and insect in nature morph their mean camberline shapes to obtain both lift and thrust simultaneously. Previous unsteady thin airfoil theories were derived mainly for a rigid flapping airfoil. An extended unsteady thin airfoil theory for a deformable airfoil is required to analyze the unsteady two-dimensional aerodynamic characteristics of a biomorphing wing. Theodorsen's approach is extended to calculate the unsteady aerodynamic characteristics of a biomorphing airfoil. The mean camberline of the airfoil is represented as a polynomial. The unsteady aerodynamic characteristics of the morphing airfoil are represented as noncirculatory and circulatory terms. Present theory can be applied to the unsteady aerodynamic analysis of a flapping biomorphing airfoil and the aeroelastic analysis of a morphing wing.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1533-1539
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• 2013

In the present study, we compared the theory with CFD data about the boundary layer thickness, displacement thickness and momentum thickness. According to the freestream velocity, larminar and turbulent is decided and affect to the flow patterns around the airfoil The boundary layer thickness, displacement thickness and momentum thickness affect to the aerodynamic characteristics of the airfoil(e.g. lift, drag and pitching moment). The separation point is affected by varying angle of attack. In the present study, we used the Joukowski airfoil(c=1), and NACA0012 airfoil was used at CFD. The chord Reynolds number is $Re_c$=3,000, 700,000, respectively and the freestream velocity is 0.045, 10 m/s, respectively. In this paper, the data was a good agreement with that of experimental results, so we can analyze the various airfoil models.

• Journal of Industrial Technology
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• v.22 no.A
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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.

• Journal of computational fluids engineering
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• v.17 no.4
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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.