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Rotational sampling in wind turbines : ウィキペディア英語版 | Rotational sampling in wind turbines
The loads on both horizontal axis wind turbines (HAWTs) and vertical axis wind turbines (VAWTs) are cyclic; that is, the thrust and torque acting on the blades is dependent on where the blade is. In a horizontal axis wind turbine, both the apparent wind speed seen by the blade and the angle of attack depend on the position of the blade. This phenomenon is described as rotational sampling. This article will provide an insight into the cyclic nature of the loads that arise because of rotational sampling for a horizontal axis wind turbine. Rotational sampling can be divided into two parts: deterministic and stochastic. Deterministic processes present themselves as spikes on a power spectrum, whereas stochastic processes are broader i.e. spread over a wider frequency range. ==Background== Analysis of the loads on a wind turbine can be carried out through use of power spectra. A power spectrum is defined as the power spectral density function of a signal plotted against frequency. The power spectral density function of a plot is defined as the Fourier transform of the covariance function.〔Remote sensing: models and methods for image processing, R. a. Schowengerdt〕〔Remote Sensing: Models and Methods for Image Processing, Robert A. Schowengerd〕 Regarding analysis of loads, the analysis involves time series, in which case the covariance function becomes the autocovariance function. In the signal processing sense, the autocovariance can be related to the autocorrelation function.
抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Rotational sampling in wind turbines」の詳細全文を読む
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