FIND DATA    SIGN UP    CONTACT US   

STATUS    SITES    RESOURCE DATA    WINDMAPS    OFFSHORE DATA  
HOME
HOWTO
SOFTWARE
LINKS
REFERENCES
ABOUT



Master of Wind Energy
new online course


MSc in Wind Energy


EWEM
European Wind Energy Master


Danish Center for Computational Wind Turbine Aerodynamics and Atmospheric Turbulence

REFERENCES



Only registered users can download documents.

Title : Wind simulation for extreme and fatigue loads.
Authors : Nielsen, M.; Larsen, G.C.; Mann, J.; Ott, S.; Hansen, K.S.; Pedersen, B.J.,

Summary :
Measurements of atmospheric turbulence have been studied and found to deviate from a Gaussian process, in particular regarding the velocity increments over small time steps, where the tails of the pdf are exponential rather than Gaussian. Principles for extreme event counting and the occurrence of cascading events are presented. Empirical extreme statistics agree with Rice’s exceedence theory, when it is assumed that the velocity and its time derivative are independent. Prediction based on the assumption that the velocity is a Gaussian process underpredicts the rate of occurrence of extreme events by many orders of magnitude, mainly because the measured pdf is non-Gaussian. Methods for simulation of turbulent signals have been developed and their computational efficiency are considered. The methods are applicable for multiple processes with individual spectra and probability distributions. Non-Gaussian processes are simulated by the correlation-distortion method. Non-stationary processes are obtained by Bezier interpolation between a set of stationary simulations with identical random seeds. Simulation of systems with some signals available is enabled by conditional statistics. A versatile method for simulation of extreme events has been developed. This will generate gusts, velocity jumps, extreme velocity shears, and sudden changes of wind direction. Gusts may be prescribed with a specified ensemble average shape, and it is possible to detect the critical gust shape for a given construction. The problem is formulated as the variational problem of finding the most probable adjustment of a standard simulation of a stationary Gaussian process subject to relevant event conditions, which are formulated as linear combination of points in the realization. The method is generalized for multiple correlated series, multiple simultaneous conditions, and 3D fields of all velocity components. Generalization are presented for a single non-Gaussian process subject to relatively simple conditions, i.e. gusts and velocity jumps. Further generalizations for simulation of multiple correlated non-Gaussian processes are suggested. Full text version is available from Risř Library as a pdf-document.

Download as PDF
 


Copyright © WindData.com

DTU

Department of Wind Energy
Technical University of Denmark
Nils Koppels Allé Building-403
Dk-2800 Kgs.Lyngby DENMARK