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.

Large vertical-axis variable-pitch wind turbine

Abstract: Several improvements are invented upon a known and well tested selfstarting vertical-axis wind turbine, for economically competitive power production by driving large grid-connected AC generators. It comprises: variable blade pitch-angle from 0 to 60 degrees, following variable wind speed for maximum efficiency and to keep constant turbine speed, variable blade camber limited to optimal lift-to-drag ratio, controled by pitch and cyclical variation of incidence-angle; improved airfoil shape of cambered blades; low cost automatic gear-train for two constant turbine speeds; protection against overload and prevention of power surge during wind gusts; low stress three-legged high tower assembled with nacelle and tail structure on ground level and erected by assembling segments of third leg one section at a time, and reducing costs of concrete footing, tower structure and, hoisting and assembling at ground level, enables a tower to be built to any height required to harness maximum wind energy.

Mathematical model for two-dimensional multi-component airfoils in viscous flow.

Abstract: A computerized analytical model of a multi-component airfoil in viscous, subsonic flow has been developed. The model, representing attached flow, defines viscous pressure distributions, lift, moments, and local boundary-layer properties on each element of an arbitrarily arranged slotted airfoil. The final viscous solution is obtained by an iterative technique for successively combining an inviscid solution with boundary-layer displacement thicknesses. Ordinary boundary-layers include laminar, transition, and turbulent types. A significant feature of the program is an analytical model representing the merging of the upper surface boundary layer with the slot efflux. Typical correlations with experiment are provided and program applications are discussed.

Convective effects and the role of quadrupole sources for aerofoil aeroacoustics

Abstract: The present investigation of aerofoil self-noise generation and propagation concerns the effects of mean flow and quadrupole sources on the broadband noise that arises from the interaction of turbulent boundary layers with the aerofoil trailing edge and the tonal noise that arises from vortex shedding generated by laminar boundary layers and trailing-edge bluntness. Compressible large-eddy simulations (LES) are conducted for a NACA0012 aerofoil with rounded trailing edge for four flow configurations with different angles of incidence, boundary layer tripping configurations and free-stream Mach numbers. The Reynolds number based on the aerofoil chord is fixed at . The acoustic predictions are performed by the Ffowcs Williams & Hawkings (FWH) acoustic analogy formulation and incorporate convective effects. Surface and volume integrations of dipole and quadrupole source terms appearing in the FWH equation are performed using a three-dimensional wideband multi-level adaptive fast multipole method (FMM) in order to accelerate the calculations of aeroacoustic integrals. In order to validate the numerical solutions, flow simulation and acoustic prediction results are compared to experimental data available in the literature and good agreement is observed in terms of both aerodynamic and aeroacoustic results. For low-Mach-number flows, quadrupole sources can be neglected in the FWH equation and mean flow effects appear only for high frequencies. However, for higher speeds, convection effects are relevant for all frequencies and quadrupole sources have a more pronounced effect for medium and high frequencies. The convective effects are most readily observed in the upstream direction.