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.

Numerical Study of Shock Buffet on Three-Dimensional Wings

Abstract: The paper presents a computational study of the transonic shock-buffet flow instability phenomenon on three-dimensional wings. Reynolds-averaged Navier–Stokes simulations were conducted on three wing configurations, all based on the RA16SC1 airfoil, at shock-buffet flow conditions. Numerical validation is presented for the OAT15A and RA16SC1 swept wings based on wind-tunnel experiments. The simulated configurations include infinite-straight, infinite-swept, and finite-swept three-dimensional wing models of several sweep angles and span lengths. Based on the results, the effects of three-dimensional flow, wing sweep, and span length on the shock-buffet characteristics are identified. For small wing-sweep angles, the fundamental shock-buffet instability mechanism remains similar to the two-dimensional mechanism, which is characterized mainly by chordwise shock oscillations. For moderate sweep angles, a phenomenon of lateral pressure disturbance propagation is observed. This phenomenon is essentially differe...

Dynamic stall of a constant-rate pitching airfoil

Abstract: A computational study is presented for the dynamic stall of an airfoil that is pitched at a constant rate from zero incidence to a high angle of attack. The unsteady flow is simulated employing the mass-averaged NavierStokes equations and an algebraic turbulent eddy viscosity model. The approach is first validated by comparison of computed and experimental results for a pitching airfoil at low freestream Mach numbers. The computed dynamic stall events, as well as the computed effects of pitch rate and axis location, are found in qualitative agreement with experimental observations. The effect of compressibility on dynamic stall is investigated. As the freestream Mach number increases, the appearance of a supersonic region provides—through the shock/boundarylayer interaction—an additional mechanism in the dynamic stall process. The main effects of compressibility are found to be 1) a change from trailing-edge stall to leading-edge stall and 2) a reduction in the stall delay and in the attained maximum lift.

Development of Variable Camber Morphing Airfoil Using Corrugated Structure

Abstract: This paper describes the development and the wind tunnel test of a variable geometry morphing airfoil using corrugated structures. Proof-of-concept study of a morphing wing with corrugated flexible seamless flap-like structure is verified by finite element analysis, and a prototype is manufactured using carbon fiber reinforced plastics. For the actuation system, two servomotors are installed inside the prototype wing to control the airfoil shape by the chordwise tension of the connected wires. Successful actuation of the prototype wing is demonstrated under the air speed up to 30 m/s in the wind tunnel test. Basic aerodynamic properties are also evaluated in comparison to traditional airfoil with a hinged control surface. Lift increase of variable corrugated wing is recognized compared to the traditional wing when the aileron angle increases.

Aerodynamic Optimization of Supersonic Transport Wing Using Unstructured Adjoint Method

Abstract: In the application of gradient-based methods to practical aerodynamic design problems, one of the major concerns is an accurate and efficient calculation of sensitivity derivatives of an aerodynamic objective function. Sensitivity derivatives can be evaluated robustly and efficiently by using a sensitivity analysis code based either on a direct method or on an adjoint method. An adjoint method is preferable in aerodynamic designs because it is more economical when the number of design variables is larger than the total number of an objective function and constraints.

Aeroacoustic wind tunnel tests of wind turbine arfoils

Abstract: Aeroacoustic wind tunnel tests were performed for six airfoils that are candidates for use on small wind turbines. One additional airfoil (NACA 0012) was tested for comparison to benchmark data. The acoustic measurements were performed in NLR's Small Anechoic Wind Tunnel, for a range of wind speeds ( U) and angles of attack, with and without boundary layer tripping. Besides the airfoil self-noise measurements in a clean tunnel flow, the models were also tested with a turbulence grid in the nozzle, to investigate airfoil noise associated with inflow turbulence. A 48-microphone out-of-flow acoustic array was used to locate noise sources and to separate airfoil noise from extraneous wind tunnel noise. Special techniques were applied to translate acoustic source plots to absolute airfoil noise spectra. The acoustic results indicate that in a clean tunnel flow trailing edge noise is dominant for all airfoils. In the untripped condition a number of airfoils exhibit intense tones, that disappear after proper tripping is applied. Broadband trailing edge noise levels are found to scale with U 4.5 . The agreement with the benchmark data was generally good. In case of inflow turbulence, leading edge noise is dominant for all airfoils, and no difference is observed between results with and without tripping. The inflow turbulence noise levels are found to scale with U 6 . Comparison of the acoustic results for different airfoils indicates that inflow turbulence noise levels increase with increasing sharpness of the model leading edge. The directivity of both trailing edge and inflow turbulence noise is found to be symmetrical with respect to the chord. With regard to the test set-up, it was found that a treatment of porous material at the model-endplate junctions yields a reduction of broadband extraneous noise up to 10 dB. As a result, the array can look much 'deeper', which enables the detection of very low trailing edge noise levels.