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Accueil > Équipes > Turbomachines > T2 - Aéroelasticité et Aéroacoustique

Flottement fan et couplage acoustique : analyse et modélisation

Thématique 2 - Aéroélasticité et Couplage Acoustique
Période 01/03/2017-29/02/2020
Contact(s) AUBERT Stéphane
Doctorant BONTEMPS Thomas
Partenaire(s) Safran Aircraft Engines


Fan flutter is an instable aeroelastic phenomenon that may lead to severe damages if not prevented. During the design, it is crucial to be able to estimate correcly the margin between the nominal working line and the flutter limit. However, it is still nowadays a complex task due to the many aerodynamic, mechanical and acoustic phenomena involved. In particular, it has been shown that the acoustic reflection on the air intake opening may stabilize or destabilize the fan in a critical way, thus it is an important aspect to take into account in the simulations. However this point is still not completly understood.

The objectives of this work are :
- To analyse the relation between the fan vibration and the acoustic propagation/reflection around the fan during flutter.
- To develop methods to be able to reproduce numerically this interaction, in order to be better predictable on flutter margin.

To do so, several tools with different fidelity levels have been used :
- the in-house URANS solver elsA (Airbus-Safran-ONERA) with a deformable mesh, to simulate in the same computationnal domain the vibrating fan, the air intake and the space around the engine.
- the commercial acoustic potential solver Actran, to characterize acoustically the intake by modelling the fan by an perfect duct mode source.
- a combination of analytical models from S. W. Rienstra.

The three tools allow to draw a coherent panorama of the phenomenon, showing a strong correlation between the acoustic characteristics of the excited mode and the fan stability.

[en]Fan flutter is an instable aeroelastic phenomenon that may lead to severe damages if not prevented. During the design, it is crucial to be able to estimate correcly the margin between the nominal working line and the flutter limit. However, it is still nowadays a complex task due to the many aerodynamic, mechanical and acoustic phenomena involved. In particular, it has been shown that the acoustic reflection on the air intake opening may stabilize or destabilize the fan in a critical way, thus it is an important aspect to take into account in the simulations. However this point is still not completly understood.

The objectives of this work are :
- To analyse the relation between the fan vibration and the acoustic propagation/reflection around the fan during flutter.
- To develop methods to be able to reproduce numerically this interaction, in order to be better predictable on flutter margin.

To do so, several tools with different fidelity levels have been used :
- the in-house URANS solver elsA (Airbus-Safran-ONERA) with a deformable mesh, to simulate in the same computationnal domain the vibrating fan, the air intake and the space around the engine.
- the commercial acoustic potential solver Actran, to characterize acoustically the intake by modelling the fan by an perfect duct mode source.
- a combination of analytical models from S. W. Rienstra.

The three tools allow to draw a coherent panorama of the phenomenon, showing a strong correlation between the acoustic characteristics of the excited mode and the fan stability.



Figure 1 : Illustration of flutter bite in the fan map



Figure 2 : Propagation and reflection on the intake opening of an acoustic mode generated by the vibrating fan

Documents et publications associés


Bontemps, T., Aubert, S., and de Cacqueray, N., 2019. “Prediction of the acoustic influence of an intake on fan
flutter : a comparison of numerical methods”. In 13th European Conference on Turbomachinery Fluid dynamics & Thermodynamics, European Turbomachinery Society.