Effect of Geometric Uncertainties on the Aerodynamic Characteristic of Offshore Wind Turbine Blades

Benedikt Ernst,Jörg R Seume,Henning Schmitt

doi:10.1088/1742-6596/555/1/012033

Benedikt Ernst, Jörg R Seume + Show 1 more

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https://doi.org/10.1088/1742-6596/555/1/012033

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Abstract

Offshore wind turbines operate in a complex unsteady flow environment which causes unsteady aerodynamic loads. The unsteady flow environment is characterized by a high degree of uncertainty. In addition, geometry variations and material imperfections also cause uncertainties in the design process. Probabilistic design methods consider these uncertainties in order to reach acceptable reliability and safety levels for offshore wind turbines. Variations of the rotor blade geometry influence the aerodynamic loads which also affect the reliability of other wind turbine components. Therefore, the present paper is dealing with geometric uncertainties of the rotor blades. These can arise from manufacturing tolerances and operational wear of the blades. First, the effect of geometry variations of wind turbine airfoils on the lift and drag coefficients are investigated using a Latin hypercube sampling. Then, the resulting effects on the performance and the blade loads of an offshore wind turbine are analyzed. The variations of the airfoil geometry lead to a significant scatter of the lift and drag coefficients which also affects the damage-equivalent flapwise bending moments. In contrast to that, the effects on the power and the annual energy production are almost negligible with regard to the assumptions made.

Highlights

For the development of cost optimized offshore or onshore wind turbines with high reliability and low probabilities of failure, probabilistic design methods become increasingly important in order to consider several types of uncertainties
The objective of the present study is to investigate the effect of geometry variations of wind turbine airfoils on the lift and drag coefficients
The present paper has investigated the effect of geometric uncertainties on the aerodynamic lift and drag coefficients as well as on the performance and loads of an offshore wind turbine

Summary

Introduction

For the development of cost optimized offshore or onshore wind turbines with high reliability and low probabilities of failure, probabilistic design methods become increasingly important in order to consider several types of uncertainties. Model uncertainties can be subdivided into statistical uncertainties due to limited sample sizes of observed quantities and physical model uncertainties due to assumptions and simplification in the design models. In the IEC standard 61400-1 [2] the partial safety factors for fatigue design of wind turbine blades are γm = 1.20 for material properties, γn = 1.15 for the consequences of failure, and γf = 1.00 for the load.

Objectives

Conclusion