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Journal of Sensors and Sensor Systems An open-access peer-reviewed journal
J. Sens. Sens. Syst., 7, 113-122, 2018
https://doi.org/10.5194/jsss-7-113-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.
Regular research article
01 Mar 2018
Aeroacoustic analysis using natural Helmholtz–Hodge decomposition
Daniel Haufe1, Johannes Gürtler1, Anita Schulz2, Friedrich Bake2, Lars Enghardt2,3, and Jürgen Czarske1 1Laboratory for Measurement and Sensor System Techniques, Department of Electrical Engineering and Information Technology, TU Dresden, Helmholtzstr. 18, 01069 Dresden, Germany
2Institute of Propulsion Technology, German Aerospace Center (DLR), 10623 Berlin, Germany
3Institute of Fluid Dynamics and Technical Acoustics, TU Berlin, 10623 Berlin, Germany
Abstract. The analysis of aeroacoustic phenomena is crucial for a deeper understanding of the damping mechanisms of a sound-absorbing bias flow liner (BFL). For this purpose, simultaneous measurements of the sound field and the flow field in a BFL are required. The fluid velocity can serve as the measurand, where both the acoustic particle velocity and the aerodynamic flow velocity contribute and, thus, can be acquired simultaneously. However, there is a need to separate these two quantities to distinguish between them. This is challenging because they generally coincide with each other in the time domain. Due to the interaction of sound and flow in a BFL, both velocities also overlap in the temporal frequency domain, having a coherent oscillation at the acoustic frequency. For this reason, the recently developed natural Helmholtz–Hodge decomposition (NHHD) is applied to separate both quantities from the measured oscillation velocity field in the spatial domain. The evaluation of synthetic vector field data shows that the quality of the decomposition is enhanced when a smaller grid size is chosen. The velocity field in a generic BFL, necessarily recorded within a three-dimensional region of interest at more than 4000 measurement locations, is evaluated using NHHD. As a result, the measured oscillation velocity in the BFL is dominated by the flow that is related to vortices and also by irrotational aerodynamic flow. Moreover, indications for an aeroacoustic source near the facing sheet of the liner are revealed.
Citation: Haufe, D., Gürtler, J., Schulz, A., Bake, F., Enghardt, L., and Czarske, J.: Aeroacoustic analysis using natural Helmholtz–Hodge decomposition, J. Sens. Sens. Syst., 7, 113-122, https://doi.org/10.5194/jsss-7-113-2018, 2018.

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The analysis of aeroacoustic phenomena is crucial for deeper understanding of the damping mechanisms of a sound-absorbing bias flow liner. Simultaneous three-component velocity measurements of the superposed sound field and the flow field in a 3-D region of interest with over 4000 measurement points are presented. The natural Helmholtz–Hodge decomposition is applied to separate both fields from the measured velocity field in the spatial domain. This reveals new insight into the aerodynamic flow.
The analysis of aeroacoustic phenomena is crucial for deeper understanding of the damping...
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