• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.2
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• pp.1-10
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• 2006

In the present study, the aerodynamic characteristics of elliptic airfoils are investigated numerically based on the RANS equations and the S-A turbulent model on unstructured meshes. Unlike the NACA series airfoil sections, elliptic airfoils have a relatively small leading edge radius and a rounded trailing edge. Also the maximum thickness is located in the middle of the chord. This geometric characteristics are responsible for the difference in the aerodynamic characteristics from those of NACA family airfoils. To identify the aerodynamic characteristics of elliptic airfoils, the results were compared with those of NACA series airfoils with a same maximum thickness. The effect of airfoil thickness variation on the aerodynamic characteristics were also investigated.

• Journal of computational fluids engineering
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• v.15 no.4
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• pp.46-52
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• 2010

In the present work, the aerodynamic characteristics of elliptic airfoils which have a 12% thickness ratio are numerically investigated based on Reynolds-averaged Navier-Stokes equations and a transition SST model at a Reynolds number 8.0$\times$105. The numerical simulation of a synthetic jet actuator which is a well-known zero-net-mass active flow control actuator located at x/c = 0.00025, was performed to control massive flow separation around the leading edge of the elliptic airfoils. Four cases of non-dimensional frequencies were simulated at an angle of attack of 12 degree. It is found that the size of the vortex induced by synthetic jets was getting smaller as the jet frequency becomes higher. Comparison of the location of synthetic jets between x/c = 0.00025 (around the leading edge) and x/c = 0.9 (near the separation) shows that the control near the leading edge induces closed recirculation flow regions caused by the interaction of the synthetic jet with the external flow, but the control applied at 0.9c (near the trailing edge) induces a very small and weak vortex which quickly decays due to weak intensity.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.20-27
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• 2004

In this study, CFD analysis for 2D ellipse and 3D CRW UAV are performed. Furthermore, flow analysis around a hub connecting body and rotor is analyzed and a strategy to reduce the drag caused by the hub is sought. Also, the idea of fairing installation is confirmed by a wind tunnel test.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.10
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• pp.757-766
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• 2009

In the present study, the effect of delta-wing vortex generators(DWVG) on the local heat transfer of the plate fin-oval tube was experimentally analyzed for Reynolds numbers for 2000, 2500 and 3200. The local heat transfer coefficient of the fin surface for four type DWVGs was measured by the naphthalene sublimation technique. As the results, the distribution of the heat transfer coefficient at rear of DWVGs showed longitudinal contours for common flow down DWVGs and wavy contours for common flow up DWVGs. The distribution showed many cell type contours at near wall and downstream for all DWVGs. Compared to case without DWVGs in present experimental tests, all DWVGs showed the best enhancement of heat transfer at Re=2000. Of 4 cases of DWVGs, D type showed the best enhancement of heat transfer.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2390-2395
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• 2007

The present research was experimentally performed to analyze the effect of delta-wing vortex generators(DWVG) on the heat transfer of fin surface of the plate fin-oval tube. The local heat transfer coefficient of the fin surface for four kinds of DWVG's arrangement was measured by the naphthalene sublimation technique for Reynolds numbers ranging from 2000 to 3200. The results showed that the heat transfer of the plate fin-oval tube can be significantly enhanced by DWVG for relatively low Reynolds numbers.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2023-2028
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• 2008

In present study, the flow field near the fin surface of plate fin - oval tube heat exchanger with delta wing vortex generator was numerically analyzed. As results, the well developed vortex behind delta wing was observed. These vortex can improve heat transfer fin surface behind delta wing vortex generators.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.12
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• pp.931-939
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• 2013

In this paper, we try to find the lifting-line method which is applicable to the conceptual design of aircraft wings, and analyze the accuracy and coverage of the method. Two methods that are extended from the lifting-line theory of Prandtl are selected. One of the methods is Weissinger's method which imposes the velocity boundary condition at the control points located at the quarter chord, and the other is Phillips's method which combines the three-dimensional vortex lifting law. Calculations are performed for an elliptic wing, a swept back wing, and a tapered unswept wing with dihedral angle and geometric twist. The aerodynamic data of the potential flow such as spanwise distributions of circulation and downwash, lift and induced drag are obtained through calculations, and these data are compared with theoretical results and wind tunnel test data. As a result, Weissinger's method showed good accuracy and reliability regardless of wing shapes, but Phillips's method revealed inaccurate results for a swept back wing.