Abstract
This paper examines the use of proper orthogonal decomposition (POD) and singular value decomposition (SVD) to identify zones on the surface of the source that contribute the most to the sound power the source radiates. First, computational fluid dynamics (CFD) is used to obtain the pressure field at the surface of the blade in a subsonic regime. Then the fluctuation of this pressure field is used as the input for the loading noise in the Ffowcs Williams and Hawkings (FW&H) acoustic analogy. The FW&H analogy is used to calculate the sound power that is radiated by the blade. Secondly, the most important acoustic modes of POD and SVD are used to reconstruct the radiated sound power. The results obtained through POD and SVD are similar to the acoustic power directly obtained with the FW&H analogy. It was observed that the importance of the modes to the radiated sound power is not necessarily in ascending order (for the studied case, the seventh mode was the main contributor). Finally, maps of the most contributing POD and SVD modes have been produced. These maps show the zones on the surface of the blade, where the dipolar aeroacoustic sources contribute the most to the radiated sound power. These identifications are expected to be used as a guide to design and shape the blade surface in order to reduce its radiated noise.
Highlights
This paper examines the use of proper orthogonal decomposition (POD) and singular value decomposition (SVD) to identify zones on the surface of the source that contribute the most to the sound power the source radiates
The results obtained through POD and SVD are similar to the acoustic power directly obtained with the Ffowcs Williams and Hawkings (FW&H) analogy
This paper proposes a method of identifying and analyzing these zones based on the combination of Ffowcs Williams and Hawkings’ acoustic analogy (FW&H) [5] and either proper orthogonal decomposition (POD) or singular value decomposition (SVD) [6]
Summary
In addition to de Villiers’ work, Olivier’s work [15] addressed the noise of the trailing edge of NACA 0012 It used data from the OpenFOAM CFD to supply the acoustic source of the Curle analogy. Druault et al [25] [26] employed this method in the far field region to separate the acoustic contribution of the most energetic structures from the residues caused by the clean flow noise (i.e. the noise from velocity fluctuations). In the light of previous works, this study applies the POD and SVD methods to the problem of aeroacoustic noise generated by the interaction between a stationary blade and a turbulent flow in a channel. The estimation of the acoustic field based on the FW&H analogy is introduced Both the POD and SVD methods are developed.
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