Search Results

The identification/localization of propulsion noise in turbo machinery plays an important role in its design and in noise mitigation techniques. Near field acoustic holography (NAH) is the process by which all aspects of the sound field can be reconstructed based on sound pressure measurements in the near field domain. Identification of noise sources, particularly in turbo-machinery applications, efficiently and accurately is difficult due to complex noise generation mechanisms. Backward prediction of the sound field closer to the source than the measurement plane is typically an unstable “ill-posed” inverse problem due to the presence of measurement noise. Therefore regularized inversion techniques are typically implemented for noise source reconstruction. Another major source of ill-posedness in NAH inverse problems is a larger number of unknowns (sources) than available pressure measurements. A model reduction technique is proposed in this paper to address this issue.

An integrated experimental/numerical technique based on nearfield acoustical holography (NAH) is developed to identify aeroacoustic noise sources associated with turbomachinery noise sources. An efficient enhanced surface potential formulation that is applicable for the resolution of complex noise source identification is developed for this purpose. Numerical examples are presented to validate the applicability of the presently developed formulation for the identification of aeroacoustic noise sources.