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| Author(s): |
Paulo Alexandre Galarce Zavala
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Mecânica |
| Defense date: | 2012-06-03 |
| Examining board members: |
José Roberto de França Arruda;
Arcanjo Lenzi;
José Maria Campos dos Santos;
Vincent Martin;
Wim Armand Febronie Bertrand Desmet
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| Advisor: | José Roberto de França Arruda |
| Abstract | |
Identification of acoustic sources is an important analysis tool for the mechanical design improvements required to compliance with restrictive noise regulations, specially on two areas: aircraft and vehicle engineering. These two industries have to comply with the airplane fly-over noise and vehicle pass-by noise limits, respectively. This thesis has the objective to develop an identification method for aeroacoustic and moving source problems. The method based on the generalized inverse beamforming has the advantage to locate distributed sources of multipole type of radiation and is used in this thesis. The strategy is to perform verifications on simple cases, with simulations and experimental assessments. On the aeroacoustic initial testing, with a cylinder under subsonic flow, peak noise events are analyzed, and the dipole center and orientation are identified. In the following test case, two-structures in subsonic flow, the Hybrid Method and the Hybrid Generalized Inverse Mapping, both proposed in this work, allow a direct comparison of mapping levels to the conventional beamforming results, and an attenuation of the auto-powers in the cross-spectral matrix is used to improve resolution. For dipole identification, a 3D grid is used, and its orientation is identified with a component towards array, which is possible due to the use of a transfer matrix re-scaling. Directivity assessments are performed for dipole distributions and compared to far-field microphones. In the third aeroacoustic case, NACA-0012 airfoil under subsonic flow, monopole identifications are compared to DAMAS2 results from the literature. On moving source identification, two measurements are performed: passenger vehicle pass-by noise; and truck pass-by noise test. The de-Dopplerization based on grid center is adopted, and two artifices are developed: image source in transfer function; and focus compensation for source non-spherical radiation. The microphone array has a special design for improved low frequency horizontal resolution. Pass-by noise level contribution mappings are used on verifications performed from 50Hz to 7kHz using two loudspeakers with tonal and broadband noise radiation. Finally, overall performance of the generalized inverse beamforming method is discussed, presenting its advantages, e.g. multipole source detection, and limitations, e.g. sensitivity to extraneous sources (AU) | |
| FAPESP's process: | 10/01315-7 - Sound sources identification in aeroacoustics problems |
| Grantee: | Paulo Alexandre Galarce Zavala |
| Support Opportunities: | Scholarships in Brazil - Doctorate |