Topic
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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27 May 2013
TL;DR: In this article, a series of experiments performed on a NACA-12 airfoil in a low-speed open-jet anechoic wind tunnel is described, and a new analytical model of the response of a serrated leading edge is proposed, extending Amiet's theory, in the limit of arbitrary large chord.
Abstract: The paper is about the sound produced as turbulence impinges on the leading edge of an airfoil and its reduction by means of either leading-edge serrations (tubercles) or the use of porous materials. The first part describes a series of experiments performed on a NACA-12 airfoil in a low-speed open-jet anechoic wind tunnel. The airfoil is held between end-plates and the sound is measured in the far field in the mid-span plane The chord-based Reynolds number ranges from 1.3 105 to 2 105. Various versions of the airfoil are tested and compared to the baseline. Sound reduction is achieved by both serrations and porosity in a wide frequency range. The second part is devoted to dedicated prediction techniques. A new analytical model of the response of a serrated leading-edge is proposed, extending Amiet's theory, in the limit of arbitrary large chord. Preliminary numerical modeling is also discussed for the response of a porous aifoil to incident disturbances, based on a panel method combined with a locally-reacting impedance model.
104 citations
TL;DR: In this paper, a three-dimensional icing model was developed at ONERA to calculate ice accretion shapes for aerodynamic components that can not be predicted using conventional two-dimensional codes.
Abstract: A three-dimensional icing model has been developed at ONERA to calculate ice accretion shapes for aerodynamic components that can not be predicted using conventional two-dimensional codes. It is described, emphasizing the original parts with respect to the two-dimensional existing models. The model includes Euler inviscid flow calculation. Droplet trajectories are calculated in a three-dimensional grid. The remesh on the leading edge is adapted to follow aerodynamics singularities. The boundary layer is calculated using a mixing length formulation to model the wall roughness influence on convective heat transfer. Runback paths are integrated. The heat balance is calculated in a grid created along the runback paths. The domain of validity of the three-dimensional icing code is described; compared with the two-dimensional model this domain is wider, especially for high speeds. The three-dimensional model is shown to simulate well a uniform ice deposit on a three-dimensional rotor blade tip. Then, a comparison of the three- and two-dimensional codes on an infinite swept wing shows that the corrected two-dimensional code predicts the catch efficiency but not the ice shape. Finally, it is shown that the continuum flux hypothesis prevents the three-dimensional model from simulating correctly the "lobster tail" ice shape (nonuniform ice deposit).
104 citations
TL;DR: A computationally efficient design methodology for transonic airfoil optimization has been developed and the results showed that more than a 90% reduction in high-fidelity function calls was achieved when compared to direct high- fidelity model optimization using a pattern-search algorithm.
104 citations
Patent•
18 Dec 1986
TL;DR: In this paper, a hollow airfoil with a longitudinally extending slot in the wall is constructed by machining a passage completely through the wall from the external surface to the internal surface and which intersects the slot.
Abstract: In the fabrication of a hollow airfoil having a
longitudinally extending slot in the airfoil wall
with the slot outlet at the external surface of the
airfoil, a metering passage extending from the
coolant compartment within the airfoil to the slot
for carrying a metered amount of coolant fluid into
the slot is formed by machining a passage completely
through the wall from the external surface to the
internal surface and which intersects the slot. The
portion of the passage between the slot and the
external surface of the airfoil is blocked, such as
with a plug or by welding. With this fabrication
method metering passages for directing coolant fluid
from inside the airfoil into the slot may be formed
without access to the interior of the airfoil.
Coolant fluid from the interior flows into the slot
through the unblocked portion of the passage and
thereupon flows out of the airfoil through the slot
as a film of coolant over the surface of the
airfoil.
104 citations
TL;DR: In this paper, three co-flow jet (CFJ) airfoils with injection slot size differed by two times consecutively are calculated by using a RANS CFD solver with 1-equation Spalart-Allmaras model.
Abstract: Three co-flow jet (CFJ) airfoils with injection slot size differed by two times consecutively are calculated by using a RANS CFD solver with 1-equation Spalart-Allmaras model. At the same angle of attack(AoA), the twice larger injection slot size airfoil passes about twice larger jet mass flow rate with the momentum coefficients also nearly doubled. The CFJ airfoil with the largest slot size has the least stall angle of attack(AoA). When the injection slot size is reduced by half, the stall AoA and the maximum lift coefficient is increased. However, when the injection slot size is further reduced by half, the stall AoA is still increased, but the maximum lift coefficient is lower due to the smaller momentum coefficient. The trend of the stall AoA and maximum lift agree with the experiment. At low AoA, both the computed lift and drag agree fairly well with the experiment. At high AoA, both the lift and drag are underpredicted. The reason may be that the RANS model can not handle the turbulence mixing well at high AoA.
104 citations