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.

A numerical study of transonic buffet on a supercritical airfoil

Abstract: The flow of the BauerGarabedianKorn (BGK) No. 1 supercritical airfoil is investigated by the solution of the unsteady Reynolds-averagedNavierStokes equations with a two-equation lagged kωturbulent model.Two steady cases (M=0.71, α=1.396 deg and M=0.71, α=9.0 deg) and one unsteady case (M=0.71, α=6.97 deg), all with a far-stream Reynolds number of 20106, are computed. The results are compared with available experimental data. The computed shock motion and the evolution of the concomitant flow separation are examined. Space-time correlations of the unsteady pressure field are used to calculate the time for pressure waves to travel downstream within the separated region from the shock wave to the airfoil trailing edge and then back from the trailing edge to the shock outside the separated region. The reduced frequency so calculated agrees well with the computed buffet frequency, supporting the signal propagation mechanism for buffet proposed by Lee (Lee, B. H. K., Oscillation Shock Motion Caused by Transonic Shock Boundary-Layer Interaction, AIAA Journal, Vol. 28, No. 5, 1990, pp. 942944).

Inverse and Direct Airfoil Design Using a Multiobjective Genetic Algorithm

Abstract: Some of the advantages and drawbacks of genetic algorithms applications to aerodynamic design are demonstrated. A numerical procedure for the aerodynamic design of transonic airfoils by means of genetic algorithms, with single-point, multipoint, and multiobjective optimization capabilities, is presented. In the ® rst part, an investigation on the relative ef® ciency of different genetic operators combinations is carried out on an aerodynamic inverse design problem. It is shown how an appropriate tuning of the algorithm can provide improved performances, better adaption to design space size and topology, and variables cross correlation. In the second part, the multiobjective approach to design is introduced. The problem of the optimization of the drag rise characteristics of a transonic airfoil is addressed and dealt with using a single point, a multipoint, and a multiobjective approach. A comparison between the results obtained using the three different strategies is ® nally established, showing the advantages of multiobjective optimization.

Joined wing aircraft

Abstract: An aircraft having a fuselage and a pair of first airfoils in the form of wings extending outwardly from the vertical tail and a pair of second airfoils in the form of wings extending outwardly from the forward portion of the fuselage at a lower elevation than the first airfoils. The second wings extend rearwardly having a positive dihedral so that the tip ends of the second airfoil are located in close proximity to and may overlap the tip ends of the first wings. The pairs of wings along with the fuselage present a double triangle or diamond shape in both front elevational view and top plan view. A winglet structurally connects the tip ends of the corresponding first wings and second wings, and these winglets have airfoil surfaces which extend vertically substantially beyond the tip ends of the first and second wings in order to minimize the effects of induced drag and also to augment directional stability of the aircraft. In addition, a unique wing structure is disclosed where the average thickness varies along the chord of the wing to enhance resistance to the component of lift acting normal to the spanwise plane containing the centroids of the airfoils.