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.

Experiments and Analysis for a Gust Generator in a Wind Tunnel

Abstract: An experimental investigation was made of the gust field generated by a rotating slotted cylinder installed in the Duke University low-speed, closed-circuit wind tunnel. The system has a very simple configuration with low cost and can produce a controllable single or multiple harmonic gust wave in the lateral and longitudinal directions. It requires minimal power and torque input. A simplified theoretical aerodynamic model and a design estimation of the lateral and longitudinal gust flowfield is also proposed in this article. The design estimate is based on a two-dimensional dynamic lift coefficient that is given by the theoretical and experimental results. An interfering wake vortex effect is the major disadvantage of this system. Nomenclature C(k) = Theodorsen's function ICleql = magnitude of equivalent lift coefficient for rotating slotted cylinder/airfoil c = airfoil chord d = cylinder diameter dLa = airfoil lift force per span length dLrsc = rotating slotted cylinder lift force per span length e, e = gap between the o.d. of the rotating slotted cylinder and trailing edge of the airfoil, elc H, H = vertical position from tunnel bottom, HIHW Hw = height of the tunnel test section

Feasibility Study of e Transition Prediction in Navier-Stokes Methods for Airfoils

Abstract: When Navier-Stokes methods are applied in the design process for laminar airfoils, the prediction of the transition location still represents an unresolved problem. By the acceptence of the E N method as representing a convenient transition prediction tool, the requirements for coupling E N to Navier-Stokes methods will be demonstrated. In particular, the possibility to determine the laminar and turbulent viscous length scales is outlined. Based on the knowledge of the viscous layer thickness, a mesh adaption procedure can be applied. The Navier-Stokes results produced using adapted meshes are shown to be Identical to boundary-layer results, when the computed wall pressure from the Navier-Stokes solution is used as input for the boundary-layer calculation. For the validation of the necessary steps in the coupling procedure, the laminar airfoil DoAL3 was selected. This airfoil was measured in the Transonic Wind Tunnel Braunschweig facility at the DLR, German Aerospace Research Establishment. The limiting N factor for that wind tunnel was determined beforehand

Wake-Structure Formation of a Heaving Two-Dimensional Elliptic Airfoil

Abstract: This paper is prompted by a recent numerical study that shows that for a two-dimensional (2-D) elliptic airfoil undergoing prescribed heaving motion in a viscous fluid, both leading-edge vortices and trailing-edge vortices contributed to the formation of the wake structures. However, an earlier dye-visualization study on a heaving NACA 0012 airfoil appears to show that the wake structures were derived from trailing-edge vortices only. The dissimilarity in the two studies remains unclear because there is no corresponding experimental data on a 2-D heaving elliptic airfoil. In this study, digital particle image velocimetry technique was used to investigate the wake-structure formation of a 2-D elliptic airfoil undergoing simple harmonic heaving motion. For the range of flow conditions investigated here, our results show that the type of wake structures produced is controlled by when and how the leading-edge vortices interact with the trailing-edge vortices

Separation control over an airfoil at high angles of attack by sound emanating from the surface

Abstract: Active control by sound emanating from a narrow gap in the vicinity of the leading edge of a symmetrical airfoil is used to study the influence of sound on the pressure distribution and the wake at high angles of attack The results from experiments conducted at a Reynolds number based on the chord of 35,000 show that, with injection of sound at twice the shedding frequency of the shear layer, the region of separation becomes drastically reduced The shear layer is found to be very sensitive to sound excitation in the vicinity of the separation point The excitation sufficiently alters the global circulation to cause an increase in lift and reduction in drag Furthermore, experimental results describing stall and post-stall conditions compare well with the limited data available and indicate that stall is delayed by sound injection into the separated region