PhD - Inverse modal identification of free-field radiated noise from unducted rotor-stator stages: from laboratory arrays to Open Fan flight tests

Context: This postdoctoral position is part of the European project TAKE-OFF (Clean Aviation programme), which is preparing the full-scale flight demonstration of Safran Aircraft Engines’ RISE Open Fan engine on the Airbus A380 flying testbed, with the aim of reducing fuel consumption by 30 % and entering service around 2035. Without a nacelle, the engine noise sources radiate directly into free field. LMFA (École Centrale de Lyon), in collaboration with LVA (INSA Lyon), is in charge of analysing the near-field pressure data acquired in flight by microphones installed on the fuselage, in order to reconstruct the engine noise sources. Objective: To extend the modal analysis methods developed at LMFA for ducted engines [1] to unducted fans. For the first time, modal analysis will be applied to microphones located in an unconfined medium and to modes radiating under free-field conditions, and design criteria specific to this configuration will be established (spatial sampling, resolution, array-to-rotor distance relative to the array size). Description: Task 1 – Model and inverse problem. Build a set of eigenfunctions describing the radiation of an unducted rotor-stator stage (spinning modes weighted by Bessel functions [2], spherical harmonics, etc.) and embed it in a Bayesian inverse approach [1] to estimate the modal amplitudes of tonal and broadband components. Flow and fuselage effects may be accounted for through CAA computations. Task 2 – Validation on the MAMBO database.