Fedala, Djaafer (2007) Modeling of broadband noise radiated by an airfoil : application to turbomachinery. PhD thesis Mécanique, ENSAM 2007ENAM0034 p.160.
Abstract
Noise pollution is one of the most significant environmental concerns. The increase in comfort requirements and rigorous of European and global regulations made of noise reduction one of the most important issues for several industries. The main objective of this work is the development of modeling tools for broadband noise component radiated by axial fans in order to include it as an optimization criterion during their design process. This study is concentrated on two sources recognized for their significant contributions in the radiated noise: interaction of the blades with the turbulent inflow and scattering of the turbulent boundary layer eddies when convected past trailing edge. Firstly, an approach based on Amiet's analytical formulation for noise prediction of an isolated airfoil placed in a turbulent flow is carried out. Thickness effect is not taken into account in the initial Amiet's formulation. A Gaussian correction was proposed based on Gershfeld studies which improved significantly the computational results. An extension towards turbomachinery is then proposed and validated experimentally. An axial fan is placed downstream of various incident turbulent flows generated by five turbulence controlling devices. Incident turbulence is characterized by the von Kármán spectral model which is fed with hot wire measurements. Comparison of the calculated sound power spectra with the experimental ones yields a reasonable or even satisfying agreement over a large range of the audible frequency. In the second part, a hybrid model combining of Large Eddy Simulations with an integral solution in time domain of Ffowcs Willimas \& Hawkings equation is developed. A validation completed by a study of numerical errors of the acoustic code based on Formulation 1A of Farassat with a permeable surface of Di Francescontonio was performed. Two-dimensional LES of the turbulent flow around an airfoil NACA0012 reproduced the boundary layer transition and the vortex shedding. Wall-pressure spectra analysis revealed that the inflow conditions have a strong effect on the airfoil response.
| Item Type: | PhD Thesis (PhD) |
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| Thesis Supervisor: | Kouidri, Smaïne |
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| Date: | 30 November 2007 |
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| Board of examiners: | Dumas, Michel and Gerolymos, Georges and Hirsch, Charles and Kouidri, Smaïne and Lewy, Serge and Manoha, Eric and Rey, Robert |
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| Ecole Doctorale: | ED 432 ECOLE DOCTORALE SCIENCES DES METIERS DE L'INGENIEUR |
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| Discipline: | Mécanique |
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| Collection (Fonds): | ENSAM |
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| Institution: | ENSAM |
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| Subjects: | 4. Materials Science, Mechanics and Mechanical Engineering |
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| Uncontrolled Keywords: | Aéroacoustique, Bruit large bande, Amiet, Profil, Turbomachine, Ventilateur, Fflowcs Williams Hawkings, Les, Turbulence, spectre de von Kármán, Bruit d'intéraction de turbulence amont, Bruit de bord de fuite, Aeroacoustics, Broadband noise, Amiet, Airfoil, Turbomachinery, Fan, Fflowcs William Hawkings, Les, von Kármán spectrum, Turbulence interaction noise, Trailing edge noise |
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| ID Code: | 3209 |
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| Deposited By: | Ramesh Prisca |
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| Deposited On: | 20 December 2007 |
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