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Airfoil

About: Airfoil is a research topic. Over the lifetime, 24696 publications have been published within this topic receiving 337709 citations. The topic is also known as: aerofoil & wing section.


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Journal ArticleDOI
Avi Seifert1, Tomer Bachar1, D. Koss1, M. Shepshelovich1, Israel Wygnanski1 
TL;DR: In this article, the effects of oscillatory blowing as a means of delaying separation are discussed, and experiments were carried out on a follow, flapped NACA 01115 airfoil equipped with a two-dimensional slot over the hinge of the flap.
Abstract: The effects of oscillatory blowing as a means of delaying separation are discussed. Experiments were carried out on a follow, flapped NACA 01115 airfoil equipped with a two-dimensional slot over the hinge of the flap. The flap extended over 25% of the chord and was detected at angles as high as 40 deg. The steady blowing momentum coefficients could be varied independently of the amplitudes and frequencies of the superimposed oscillations. The modulated blowing was a major factor in improving the performance of the airfoil at much lower energy inputs than was hitherto known. Optimum benefits in performance were obtained at reduced frequencies, based on the flap chord, of an order of unity. Significant increase in lift as well as cancellation of form drag were observed

571 citations

Journal ArticleDOI
TL;DR: In this article, the effect of the actuation frequency, actuator location, and momentum coefficient on flow separation on a symmetric airfoil with synthetic jet actuators is investigated.
Abstract: Control of flow separation on an unconventional symmetric airfoil using synthetic (zero net mass flux) jet actuators is investigated in a series of wind tunnel tests. The symmetric airfoil comprises the aft portion of a NACA four-digit series airfoil and a leading edge section that is one-half of a round cylinder. The experiments are conducted over a range of Reynolds numbers between 3.1 × 10 5 and 7.25 × 10 5 . In this range, the flow separates near the leading edge at angles of attack exceeding 5 deg. When synthetic jet control is applied near the leading edge, upstream of the separation point, the separated flow reattaches completely for angles of attack up to 17.5 deg and partially for higher angles of attack. The effect of the actuation frequency, actuator location, and momentum coefficient is investigated for different angles of attack. The momentum coefficient required to reattach the separated flow decreases as the actuators are placed closer to the separation point. In some cases, reattachment is also achieved when the actuators are placed downstream of the stagnation point on the pressure side of the airfoil

563 citations

Book ChapterDOI
01 Jan 1999
TL;DR: In this article, the authors presented the first true applications of Detached-Eddy Simulation (DES), in the sense of being three-dimensional, and treated an airfoil in the challenging regime of massive separation, in that lift and drag are within 10% of the experimental results at all angles of attack, to 90°.
Abstract: We present the first true applications of Detached-Eddy Simulation (DES), in the sense of being three-dimensional. DES was defined in 1997 with hopes of combining the strengths of Reynolds-averaged methods and of Large-Eddy Simulations, in a non-zonal manner, to treat separated flows at high Reynolds numbers. We first simulate isotropic turbulence, to check the concept in LES mode and set its adjustable constant. Smooth inertial ranges are obtained up to the cutoff in the spectra. We then treat an airfoil in the challenging regime of massive separation and do so very successfully, in that lift and drag are within 10% of the experimental results at all angles of attack, to 90°. Such an accuracy is not achieved with traditional modelling, even unsteady, which gives up to 40% error. Cost puts a pure LES of the same flow (at Reynolds number 105 and beyond) out of reach on any computer, yet we use personal computers for the DES, and about 200,000 grid points. On the other hand, grid refinement, domain-size and Reynolds-number studies have not been completed yet. Hysteresis in the 15 - 25° range has not been addressed.

527 citations

Journal ArticleDOI
TL;DR: In this article, the authors defined the upper surface lift coefficient of an airfoil chord and defined the freestream conditions at the leading edge of the chord line, and the ratio of specific heats.
Abstract: Nomenclature c = airfoil chord CL = lift coefficient = L/!/2pV00c CLu = upper-surface lift coefficient Cp = pressure coefficient = (p -p^)/ Ap Vx 2 Mx = freestream Mach number p = static pressure Re^ = freestream Reynolds number based on airfoil chord = V^clv sp = location of leading-edge stagnation point V^ — freestream velocity v local velocity on airfoil surface x = distance along chord line F = circulation about the airfoil 7 = ratio of specific heats v = kinematic viscosity p = density () oo = freestream conditions () t e = conditions at the airfoil trailing edge

522 citations

Proceedings ArticleDOI
TL;DR: In this paper, an overview of the design and wind tunnel test results of the wind turbine dedicated airfoils developed by Delft University of Technology (DUT) is given.
Abstract: This paper gives an overview of the design and wind tunnel test results of the wind turbine dedicated airfoils developed by Delft University of Technology (DUT). The DU-airfoils range in maximum relative thickness from 15% to 40% chord. The first designs were made with XFOIL. Since 1995 RFOIL was used, a modified version of XFOIL, featuring an improved prediction around the maximum lift coefficient and capabilities of predicting the effect of rotation on airfoil characteristics. The measured effect of Gurney flaps, trailing edge wedges, vortex generators and trip wires on the airfoil characteristics of various DU-airfoils is presented. Furthermore, a relation between the thickness of the airfoil leading edge and the angle-of-attack for leading edge separation is given.Copyright © 2003 by Delft University of Technology

485 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,083
20221,871
2021923
2020979
20191,097
20181,002