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.

Vertical axis wind engine

Abstract: A vertical axis wind engine, also referred to as a vertical axis wind turbine (VAWT) includes a support structure, a rotor mounted rotatably on the support structure for rotation about a vertical axis, and at least one airfoil for causing the rotor to rotate about the vertical axis in response to wind passing the wind engine. The airfoil has vertically extending leading and trailing edges, an angle-of-attack axis extending horizontally through the leading and trailing edges, and a pivotal axis extending vertically intermediate the leading and trailing edges. The airfoil is mounted on the rotor for pivotal movement about the pivotal axis and the rotor includes components for limiting pivotal movement of the airfoil to first and second limits of pivotal movement. The airfoil is free to pivot about the pivotal axis intermediate the first and second limits of pivotal movement as the rotor rotates about the vertical axis in order to thereby enable the airfoil to align the angle-of-attack axis according to the wind. Preferably, the wind engine has more than one free-flying, self-positioning airfoil, and the rotor includes first and second stops for each airfoil that augment virtual stop effects to limit pivotal movement to a radially aligned first limit and a tangentially aligned second limit. According to another aspect of the invention, multiple wind engines are stacked. Yet another aspect provides an exponentially shaped structure surrounding the vertical axis that funnels wind toward the rotor.

Flow directing assembly for the compression section of a rotary machine

Abstract: An inner and/or outer cylindrical wall limiting the working fluid flow path of an axial compressor radially has an ondulating contour. At the intersection with the leading edge of an airfoil the wall shows a convex contour (54) followed by a concave contour (58) in the region of the airfoils maximum thickness while at the intersection with the trailing edge of the airfoil the contour (56) is convex again. The airfoil can either be a rotor blade or a stator vane.

Control of Flow Past a Wing Section with Plasma-based Body Forces

Abstract: : The response of the flow past a stalled NACA 0015 airfoil at 15 deg angle of attack and Reynolds number of 45, 000 to body forces originating from radio-frequency asymmetric dielectric-barrier-discharge actuators is described via direct numerical simulations. The theoretical model couples a phenomenologically derived averaged body force with a high-order 3-D compressible Navier-Stokes solver. The body force distribution is assumed to vary linearly, diminishing away from the surface until the critical electric field limit is reached. Various magnitudes and orientations of the force field are explored, ranging from vertically upwards (away from the body) to vertically downwards (towards the body). The imposed body forces couple to the non-linear inertial terms and the pressure gradients to engender a complex sequence of events. A significant streamwise component assures the reduction or elimination of stall with the formation of a stable wall-jet. When the only component of the force vector is pointed normal to and away from the surface, no control effect is achieved. On the other hand, when the force vector is directed towards the surface, a shallower separation region is observed, accompanied by unsteady boundary layer development. At the low Mach number considered (0.1), the work done by the force has little impact on the solution, and density variations remain less than 5%. Relaxation effects are explored by abruptly switching off the force, and estimates of response times are noted. The lack of a proper spanwise breakdown mechanism for the separated shear layer in 2-D simulations results in large coherent structures, whose response in transient and unsteady asymptotic states differ significantly from those observed in 3-D. Nonetheless, if the force is sufficiently effective to eliminate separation, the flowfield becomes generally two-dimensional and steady in the vicinity of the airfoil, and the overall results from 2-D and 3-D analyses yield similar results.

Experimental Investigation of Jet Mixing Mechanism of Co-Flow Jet Airfoil

Abstract: The jet mixing of a co-flow jet (CFJ) airfoil is investigated to understand the mechanism of lift enhancement, drag reduction, and stall margin increase. Digital Particle Image Velocimetry, flow visualization and aerodynamic forces measurements are used to reveal the insight of the CFJ airfoil mixing process. At low AoA and low momentum coefficient, the mixing between the wall jet and mainflow is dominant with large structure coherent structures for the attached flows. When the momentum coefficient is increased, the large vortex structure disappears. At high AoA with flow separation, the CFJ creates a upstream flow strip between two counter rotating vertical shear layer, i.e., the outer shear layer and inner flow induced by CFJ. The UFS is characterized with large vortex free region. The co-flow wall jet is deflected normal to the airfoil surface characterized with a saddle point. With increased momentum coefficient of the CFJ, the saddle point moves downstream and eventually disappears when the flow is attached. Turbulence plays a key role in mixing the CFJ with mainflow to transport high kinetic energy from the jet to mainflow so that the mainflow can remain attached at high AoA to generate high lift. When the flow is separated, increased CFJ momentum coefficient also increases the turbulence intensity at jet injection mixing region.