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Le 21 avril 2017 à 14h00

PhD Defense: Laura LACASSAGNE – Numerical simulations and linear stability analysis of corner vortex shedding in solid rocket motors


Summary :

Pressure oscillations (ODP) are a major issue in solid rocket motor design, as very small pressure oscillations induce strong thrust oscillations, involving vibrations detrimental to carrying load. ODP are still a vast and intense domain of research and the improvement of rocket motors mainly resorts to advanced numerical simulations. Extensive research have enabled to characterize several sources of instabilities, but new motor design promotes one hydrodynamic instability, called VSA and characterized by vortex shedding at geometry angles. VSA has be studied in the C1x configuration [Vuillot 1995, Dupays 1996] but several points still need to be studied in order to have a complete view of the phenomena driving and impacting this instability in a solid rocket motor flow. In this work, the VSA is isolated in an academic configuration and, in a first part, the impact of lateral blowing is studied. This blowing, never analysed so far, is due to burnt gases coming from the combustion of propellant block after the angle. This study has been performed following two approaches, numerical simulations and linear stability analysis.  Both demonstrate the strong stabilizing effect of the lateral blowing.  In a second part, the impact of aluminium particles combustion including the presence of residual particles, found in solid rocker motors, is analysed. This work shows that due to complex interaction mechanisms, particles can have a stabilizing or a destabilizing impact on the instability. Finally, the scaling impact is studied with a without particles. In purely gaseous configuration, the results obtained at reduced scale can be used directly at real scale as all the characteristics of the instability are preserved. However, with particles, the scaling modifies the particles behaviour and then the particles impact on the VSA.

Members of the Jury :

M. Frédéric PLOURDE, Research Director, ENSMA, Referee
M. Franck RICHECOEUR, Professor, EM2C, Referee
Mrs Bénédicte CUENOT, Research Director, CERFACS, Advisor
M. Jérôme ANTHOINE, Research Fellow, ONERA, Member
M. Grégoire CASALIS, Professor, ISAE-Supaero, Member
M. Lutz LESSHAFFT, Research Fellow, LadHyX, Member
M. Franck GODFROY, Engineer, ASL/CRB, Invited
M. Franck NICOUD, Professor, Montpellier University, Invited
M. Thierry PEVERGNE, Engineer, ASL, Invited