Alice DINSENMEYER : Inverse methods for aero-acoustic source characterization

From 1 July 2017 to 31 July 2020
Date of thesis defence: 12 october 2020

Research laboratories : LVA (INSA Lyon) et LMFA (ECL)
Thesis Directors : J. Antoni, C. Bailly, Q. Leclère

Topic:

Understanding the physical phenomena that lead to the generation of aero-acoustical sources is crucial to reduce the noise annoyances. These phenomena are studied using experiments or numerical simulations. In both cases, pressure maps are obtained from outside of the turbulent flow, from which the sources are generated. This turbulent area is indeed difficult to access experimentally with a non-intrusive set-up. Moreover, the pressure measurements are dominated by the effects of turbulence and the acoustic sources are therefore difficult to characterize. Inverse methods are preferably used for this purpose, based on measurements done outside of the turbulent flow. In the aero-acoustic field, many approaches exist, such as beamforming coupled with deconvolution methods that improve imaging resolution (DAMAS, CLEAN, ...).
The main objective of this thesis is to address this source identification issue in a probabilistic framework. This approach is barely used in the aero-acoustic field because its application can be difficult without an appropriate regularization of the problem. But progress have been made last years and this approach could be suitable for aero-acoustic applications, especially when the sources have specific correlation length, whereas beamforming methods hardly deal with correlated sources. This approach could also improve source level reconstruction.