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In the present paper the fluid-structure-acoustic interaction of a thin flexible structure in the wake of a wall-mounted square cylinder is investigated experimentally. The experiments are performed in an acoustics wind tunnel employing microphone measurements of the sound pressure level. Detailed flow measurements are carried out using laser-Doppler anemometry and 3D-hot-wire anemometry. The flow induced vibration of the flexible structure is measured with a laser scanning vibrometer. Experimental results characterizing the flow field, the structural vibration and the generated sound are presented.

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In many technical applications the interaction between a fluid flow and a thin flexible structure leads to the generation of acoustic noise which is caused by flow induced structural vibrations. Examples for such applications are coverings and panelings of cars and airplanes. In many cases the generated noise is unwanted so that noise reduction is a topic of major interest. In the present work we investigate the acoustic field resulting from the interaction of a thin flexible structure with a turbulent flow field by means of numerical simulation. Two different model configurations are considered: one is the flow over a flexible plate, in the second case the flexible plate is located in the wake of a square cylinder. The major aim of this work is to provide a better understanding of the noise generation processes in these flow cases. The numerical methodology applied is utilized for a decomposition of the acoustic field into one part generated by the structural vibrations and another part which is due to stream noise. Finally, comparisons to experimental data available at our institute are provided.

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