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  • 1
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    Overview of Wind Energy Systems: Issues in Development and Application (1981)
    American Society of Mechanical Engineers
    Details
    Publication Date: 1981-02-01
    Description: An overview of the current status of wind energy technology and system development is presented with major emphasis placed on the key issues which face the commercialization of wind technology. The basic fundamentals of the technology are reviewed and the direction of current development is outlined. Economic considerations are discussed both from a machine development point of view and the utility-industry cost-of-service approach. In addition, the problems associated with wind turbine performance testing are discussed and a short review of operational experience is provided. These topics are all considered in the context of providing the reader with an understanding of wind system technology, a general knowledge of current problems, and the expected trends for the future. Many of these important issues are still under intensive investigation, and in some cases, a clearly superior solution has not emerged. In these circumstances, the value judgments are properly left to the reader.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Society of Mechanical Engineers
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  • 2
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    A Comparison of Predicted Wind Turbine Blade Loads to Test Measurements (1988)
    American Society of Mechanical Engineers
    Details
    Publication Date: 1988-08-01
    Description: The accurate prediction of wind turbine blade loads and response is important in predicting the fatigue life of wind machines. At the SERI Wind Energy Research Center, a rotor code called FLAP (Force and Loads Analysis Program) is currently being validated by comparing predicted results to machine measurements. The FLAP code has been modified to allow the teetering degree of freedom. This paper describes these modifications and comparisons of predicted blade bending moments to test measurements. Wind tunnel data for a 1/20th scale model will be used to compare FLAP predictions for the cyclic flap-bending moments at the 33 percent spanwise station for three different wind speeds. The comparisons will be made for both rigid and teetering hubs. Currently, the FLAP code accounts for deterministic excitations such as wind shear, tower shadow, gravity, and prescribed yawing motions. Conclusions will be made regarding the code’s accuracy in predicting the cyclic bending moments.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Society of Mechanical Engineers
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  • 3
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    A Computer Analysis of Wind Turbine Blade Dynamic Loads (1986)
    American Society of Mechanical Engineers
    Details
    Publication Date: 1986-02-01
    Description: The flapping motion of a single wind turbine rotor blade has been analyzed and equations describing the flapping motion have been developed. The analysis was constrained to allow only flapping motions for a cantilevered blade, and the equations of motion are linearized. A computer code, called FLAP (Force and Loads Analysis Program), to solve the equations of motion and compute the blade loads, has been completed and compared to measured loads for a 3-bladed downwind turbine with stiff blades. The results of the program are presented in tabulated form for equidistant points along the blade and equal azimuth angles around the rotor disk. The blade deflection, slope and velocity, flapwise shear and moment, edgewise shear and moment, blade tension, and blade torsion are given. The deterministic excitations considered in the analysis include wind shear, tower shadow, gravity, and a prescribed yaw motion.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Society of Mechanical Engineers
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  • 4
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    Structural Dynamic Analysis of Wind Turbine Systems (1982)
    American Society of Mechanical Engineers
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    Publication Date: 1982-05-01
    Description: The paper presents an overview of the dynamic analysis of horizontal axis wind turbines. The major emphasis of the paper is the review of current analysis methods and the comparison of results with experimental data. The current capabilities for predicting turbine system natural frequencies are discussed and the design implications of frequency placement are reviewed. The prediction of cyclic loads, using the dynamic analysis computer codes, is examined and comparisons are made between the code predictions and field test data. Finally, the dynamic analysis needs for advanced turbine systems are considered.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Society of Mechanical Engineers
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  • 5
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    Prediction of Stochastic Blade Responses Using Measured Wind-Speed Data as Input to the Flap Code (1990)
    American Society of Mechanical Engineers
    Details
    Publication Date: 1990-11-01
    Description: Accurately predicting wind turbine blade loads and response is important in predicting the fatigue life of wind turbines. The necessity of including turbulent wind effects in structural dynamics models has long been recognized. At SERI, the structural dynamics model, or FLAP (Force and Loads Analysis Program), is being modified to include turbulent wind fluctuations in predicting rotor blade forces and moments. The objective of this paper is to show FLAP code predictions compared to measured blade loads using actual anemometer array data and a curve-fitting routine to form series expansion coefficients as the turbulence input to FLAP. The predictions are performed for a three-bladed upwind field test turbine. An array of nine anemometers was located 0.8 rotor diameters (D) upwind of the turbine, and data from each anemometer are used in a least-squares curve-fitting routine to obtain a series expansion of the turbulence field over the rotor disk. Three 10-min data cases are used to compare FLAP predictions to measured results. Each case represents a different mean wind speed and turbulence intensity. The time series of coefficients in the expansion of the turbulent velocity field are input to the FLAP code. Time series of predicted flap-bending moments at two blade radial stations are obtained, and power spectra of the predictions are then compared to power spectra of the measured blade bending moments. Conclusions are then drawn about the FLAP code’s ability to predict the blade loads for these three data cases. Recommendations for future work are also made.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Society of Mechanical Engineers
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  • 6
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    Wind turbulence inputs for horizontal axis wind turbines (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Wind turbine response characteristics in the presence of atmospheric turbulence was predicted using two major modeling steps. First, the important atmospheric sources for the force excitations felt by the wind turbine system were identified and characterized. Second, a dynamic model was developed which describes how these excitations are transmitted through the structure and power train. The first modeling step, that of quantifying the important excitations due to the atmospheric turbulence was established. The dynamic modeling of the second step was undertaken separately.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Research Center Wind Turbine Dyn.; p 101-112
    Format: application/pdf
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  • 7
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    Stress-intensity factors for a surface crack in a finite solid. (1972)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A solution to the problem of a circular crack partially embedded in a solid of finite thickness is presented. A superposition and iteration technique is used to determine the stress-intensity factor numerically. The stress-intensity factor is determined as a function of position around the crack front for a variety of crack depths. The results of this study are compared with experimental data for a semielliptical surface flaw in a brittle material.
    Keywords: STRUCTURAL MECHANICS
    Type: ASME PAPER 71-APMW-6
    Format: text
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  • 8
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    The partially closed Griffith crack (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A solution is presented for a Griffith crack subjected to an arbitrary polynomial loading function which causes one end of the crack to remain closed. Closed form expressions are presented for the crack opening length and for the stress and displacements in the plane of the crack. The special case of pure bending is presented as an example and for this case the stress intensity factor is computed.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 9; Mar. 197
    Format: text
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  • 9
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    Wind response characteristics of horizontal axis wind turbines (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: It was the objective of the work reported here, and in the companion paper 1 . A broader examination of wind turbine dynamic response to turbulence, and attempts to ascertain the features of turbulence that wind turbines are most sensitive to were made. A statistical description of the wind input including all three wind components and allowing linear wind gradients across the rotor disk, was used together with quasi-static aerodynamic theory and an elementary structural model involving only a few degrees of freedom. The idea was to keep the turbine model simple and show the benefits of this type of statistical wind representation before attempting to use a more complex turbine model. As far as possible, the analysis was kept in the simplest form, while still preserving key physical responses.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Research Center Wind Turbine Dyn.; p 87-99
    Format: application/pdf
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  • 10
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    Wind Turbine Dynamics (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Recent progress in the analysis and prediction of the dynamic behavior of wind turbine generators is discussed. The following areas were addressed: (1) the adequacy of state of the art analysis tools for designing the next generation of wind power systems; (2) the use of state of the art analysis tools designers; and (3) verifications of theory which might be lacking or inadequate. Summaries of these informative discussions as well as the questions and answers which followed each paper are documented in the proceedings.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CP-2185 , NAS 1.55:2185 , CONF-810226 , SERI/CP-635-1238
    Format: application/pdf
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