Rotational sampling in wind turbines: Difference between revisions

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{{Further|Wind turbine design}}

{{Issues|

{{RefimproveMore citations needed|date=October 2013}}

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The loads on both [[horizontal-axis wind turbine]]s (HAWTs) and [[vertical-axis wind turbine]]s (VAWTs) are cyclic; the [[thrust]] and [[torque]] acting on the blades depend 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]] depends on the blade's position. This phenomenon is described as '''rotational sampling'''. This article will provide 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 system|deterministic]] and [[Stochastic process|stochastic]]. Deterministic processes present themselves as spikes on a [[Power spectral density|power spectrum]], where as stochastic processes spread over a wider [[frequency range]].

{{Further|Wind turbine design}}

==Background==

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* Tower shadow <ref>Time-Domain Modeling of Tower Shadow and Wind Shear in Wind Turbines,

Swagata Das, Neeraj Karnik, and Surya Santoso</ref>

* [[Wind shear]] <ref>Time-Domain Modeling of Tower Shadow and Wind Shear in Wind Turbines,

Swagata Das, Neeraj Karnik, and Surya Santoso</ref>

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</math>

The [[covariance]] function of a sum of [[Sinusoidal model|sinusoids]] is itself a sum of [[Sinusoidalsinusoidal function|sinusoidal functions]]s. Thus, the power spectral density function is a set of Dirac delta functions. The locations of these are at multiples of ''n''. Thus, on a power spectrum, deterministic processes such as gravitational loading manifest themselves as spikes. This can be seen from analysing generator torque.

====Blades====

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{{Reflist}}

[[Category:Wind turbines]]

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[[Category:Wind turbines]]