S Worasinchai, G Ingram and R Dominy, SAGE and Institution of Mechanical Engineers, 18 July 2011
This article describes an experimental, aerodynamic investigation of four aerofoils intended for small wind turbine applications. The aerofoils of these small machines (both horizontal and vertical axes) normally experience conditions that are quite different from large-scale machines due to smaller chord length and lower wind speed, resulting in significantly lower Reynolds numbers. They also operate with an unusually wide range of incidence angles (0° to 90° for horizontal axis and 0° to 360° for vertical axis). Four appropriate aerofoils were chosen for testing at three Reynolds numbers (65000, 90000, and 150000) through 360° incidence to cover almost all possible conditions that might be encountered by both types of turbines...
David R. Malcolm, Sandia National Laboratories, July 1988
This report describes a project intended to incorporate the effects of atmospheric turbulence into the structural .response of Darrieus rotor, vertical axis wind turbines. The basis of the technique is the generation of a suitable time series of wind velocities, which are passed through a double multiple streamtube aerodynamic representation of the rotor. The aerodynamic loads are decomposed into components of the real eigenvectors of the rotor and subsequently into full-power and cross-spectral densities. These modal spectra are submitted as input to a modified NASTRAN random load analysis and the power spectra of selected responses are obtained. This procedure appears to be successful. Results at zero...
Robert E. Akins, Dale E. Berg, W. Tait Cyrus, Sandia National Labs, October 1987
This report describes measurements of aerodynamic torque on a vertical-axis wind turbine. Accelerometers mounted at the equator of the rotor and a torque meter mounted at the base of the rotor were used to compute the net aerodynamic torque acting on the rotor. Assumptions concerning blade- response symmetry were required to achieve blade torque as a function of rotor position on each half of a revolution for a two-bladed rotor. Results are presented for tip-speed ratios from 2.5 to 8.0 for two turbine rotational speeds. Evidence of dynamic stall is observed at low tip-speed ratios.
Paul S. Veers, Sandia National Laboratories, September 1984
The Vertical AXIS Wind Turbine (VAWT) is a machine which extracts energy from the wind. Since random turbulence is always present, the effect of this turbulence on the wind turbine fatigue life must be evaluated. This problem is approached by numerically simulating the turbulence and calculating, In the time domain, the aerodynamic loads on the turbine blades. These loads are reduced to the form of power and cross spectral densities which can be used in standard linear structural analysis codes. The relative importance of the turbulence on blade loads is determined.