Wind Turbine Aerodynamics
Extensive industrial sponsorship attracted by Virginia Tech’s unique capabilities has led to a broad range of research and testing in blade aerodynamics, led by faculty in the AOE. Wind turbine blades have very different requirements than those of winged vehicles. They are designed to be aerodynamically aggressive, maximizing power generation, and operating close to performance limits. They must accommodate extreme structural loads that vary dramatically over the blade radius. At the same time they must be robust enough to operate in a turbulent environment, over extreme ranges of conditions, with lower shape tolerances and with accumulation of dirt and debris. The blades not only are the source of power generation they are also the only mechanism for controlling the motion of a wind turbine to accommodate changing conditions, to coordinate with other turbines in a farm, or simply to stop. These and other factors make the aerodynamics of these blades a scientifically very fertile area.
The Virginia Tech research portfolio in experimental aerodynamics touches many of these issues. Current and recent topics in aerodynamics include numerous studies of aerodynamically aggressive airfoils, thick airfoils designed for blade midspan and root, laminar flow airfoils for high power generation efficiency, airfoils at extreme angles for control authority and feathering, flow control aerodynamics to mitigate blade loads during extreme maneuvers, aerodynamic tolerances for blade design and fouling. A new and particularly exciting area of aerodynamic and acoustic research, in collaboration with GE and NREL, is in the development of the understanding needed to fabricate wind turbine blades using fabric stretched across a frame, in place of the conventional fiberglass construction. This promises a substantial reduction in wind energy cost
A significant companion our wind energy efforts, and an important part of maintaining internationally recognized capabilities, is research and rapid progress in the science of aerodynamic testing itself. This includes current efforts in instrumentation development, in wind tunnel corrections and in relating wind tunnel tests to computational simulations.
Computational Aerodynamics and Turbulence Modeling
Accompanying the university’s presence in experimental wind turbine aerodynamics are substantial programs and capabilities in aerodynamic simulation and modeling. Virginia Tech AOE faculty and students, led by Prof. Eric Paterson, are collaborators with colleagues at Penn State University and NCAR on a $1.2 M DOE-funded research project to develop a “Cyber Wind Facility (CWF),” which is a wind-turbine-level (vs. farm-level) simulation suite of tools for generating highly-resolved 4D predictions of wind turbine behavior. The CWF uses the OpenFOAM library and can simulate the atmospheric boundary-layer turbulence and coupled aerodynamics of the rotating blades, as well as the ocean waves and platform motions of an offshore wind turbine installation. In addition the CWF predicts blade and tower elastic deformations, and wake turbulence for wake-turbine interactions. Find more information.
Wind Turbine Aeroacoustics
A critical environmental and social problem of large wind turbines is noise pollution. Characterizing the noise generated by wind turbine blades and components is the focus of work being done in Virginia Tech’s Department of Mechanical Engineering, in collaboration with AVEC Incorporated. Identifying noise sources as distinct from background sound is a very challenging task, particularly in testing situations where the background sound may be louder than the sources of interest. Microphone phased array technology is the state-of-the-art tool for aeroacoustic measurements. A microphone phased array is a collection of a large number of microphones whose signals are digitally processed to focus the array to points on the airfoil model and determine the noise radiated. The outcome of this process is the generation of acoustic maps showing where the noise is generated on the airfoil and its spectral content while eliminating other sources.