Advanced investigation into the influence of high frequency turbulence on wind turbine blades
Daniela Schwab, Alois Schaffarczyk
University of Applied Sciences Kiel
Mechanical Engineering Department
Grenzstraße 3, 24149 Kiel, Germany
Abstract
In order to design wind turbines knowledge of the flow field including the high frequency part and the boundary layer at the rotor blade is important. Due to the complexity of the experimental setup, only few results exist. For this reason two research projects are conducted at the University of Applied Sciences in Kiel:
The objective of the first project is the examination of onshore / offshore wind fields and the measurement of high frequency aerodynamic turbulence by a piezo electric transducer. Onshore measurements show that time-averaged parameters like the turbulence intensity are comparable to those of cup anemometers and that there is no clear difference between the measurements from sea- and landside. The decrease of the obtained power spectral density follows a power law with a comparable exponent as those of Kolmogrow. The offshore measurements will be realized at FINO3, a research measurement platform, which will start operating in summer 2010.
By means of a so called aerodynamic glove the boundary layer at a wind turbine blade during rotation under normal working conditions is investigated. The purpose of this project is to develop and install the measuring setup, which consists of pressure taps in circumferential direction and a hot-film to determine the state of the boundary layer: laminar or turbulent. The experimental results shall at first enlarge the experimental database.
Both measurements are accompanied by CFD calculations of two-dimensional blade profiles and stability analysis of the boundary layer by a simplified eN-method. Initial calculations point up the influence of the N-factor on the results and the need of its accurate determination.
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Advanced investigation into the influence of high frequency turbulence on wind turbine blades
