PhD defense - J. Richard

Delivered by Université Montpellier II - Sciences et Techniques du Languedoc
Speciality: Mathematics


December 7, 2012 - CERFACS

Large solid propellant rocket motors may be subjected to aero-acoustic instabilities arising from a coupling between the burnt gas flow and the acoustic eigenmodes of the combustion chamber. These instabilities lead to large pressure oscillations in the combustion chamber. These pressure oscillations cause vibrations which might jeopardize the payload if they happen to be larger than a certain threshold. Given the size and cost of any single firing test or launch, it is of first importance to rely on numerical tools able to predict these instabilities so that they can be avoided at the design level. The first purpose of this thesis is to build a numerical tool in order to evaluate how the coupling of the fluid flow and the whole structure of the motor influences the amplitude of the aeroacoustic oscillations living inside the rocket. A particular attention was paid to the coupling algorithm between the fluid and the solid solvers in order to ensure the best energy conservation through the interface. The numerical chain is applied to a sub-scaled configuration of Ariane 5 solid rocket motor in two studies. The first relates to the impact of vibration of the structure on aeroacoustic instabilities. The effect of a crossover frequency between the longitudinal modes of the structure and the acoustic modes of the combustion chamber is assessed. The second study examines the effect of thermal protection oscillations in the flow. An increased of the flow organisation and a significant strengthening of pressure oscillations are highlighted.

C. Bailly	Ecole Centrale de Lyon	Referee
E. Lefrançois	Université of Technologie de Compiègne	Referee
F. Vuillot	ONERA	Member
B. NKonga	Université de Nice-Sophia Antipolis	Member
J. Anthoine	ONERA	Member
D. Di Pietro	Université Montpellier II	Member
G. Pevergne	SPS Le Haillan	Invited Member
G. Staffelbach	CERFACS	Co advisor
F. Nicoud	Université Montpellier II	Advisor

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