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DY: Fachverband Dynamik und Statistische Physik

DY 33: Poster II

DY 33.34: Poster

Donnerstag, 14. März 2013, 17:00–19:00, Poster C

Correlation between active grid excitation and generated wind field — •Gerrit Kampers, Nico Reinke, Joachim Peinke, and Michael Hölling — ForWind - Center for Wind Energy Research, Institute of Physics, University of Oldenburg, Germany

Turbulence plays an important role in the field of wind energy conversion. Lift forces and their fluctuations, for example, are strongly influenced by the statistics of the ambient wind field. For realistic wind tunnel investigations, an active grid was build, which allows the generation of wind fields with comparable characteristics to those in the atmospheric boundary layer (ABL). The active grid consists of seven horizontal and nine vertical axes with fixed 7.4 × 7.4 cm² square flaps. Each of these axes can be controlled individually by a step motor.
A challenging part in the work with the active grid is to find the right excitation protocols to control the position in time of the axes, and therefore the stochastical properties of the resulting turbulent flow field. The goal is to create realistic flow fields, e.g. fields with heavy intermittency, which is one of the major properties of the ABL.
To achieve that, the interaction between the active grid excitation and the resulting flow field was investigated experimentally. In the experiments, the angle of attack and the rotation speed of the flaps were successively changed for different wind speeds. The resulting flow field was measured with hot-wires at several downstream positions. Based on the experiments, a model for the excitation - flow field interaction was developed. The model allows for a more systematic creation of excitation protocols for different flow properties.