PhD defense - O. Cabrit

Wall modeling of the flow inside solid rocket motor nozzles

Delivered by University of Montpellier II
Speciality: Mathematics

December 3, 2009 - CERFACS

The nozzles of solid rocket motors must resist to severe wall fluxes. Carbon/carbon composite materials are then chosen to insure the structure integrity. In spite of their excellent thermo-mechanical properties, these materials are exposed to the ablation phenomenon: chemical oxidation of the solid material by the combustion products. On the one hand, this feature protects the nozzle structure since this process considerably reduces the wall heat flux. On the other hand, the ablation process must be perfectly controlled because of the geometrical changes induced by the surface recession. The assessment of mass/momentum/heat fluxes at the wall is thus a crucial part for the nozzle design. 

Numerical simulations are nowadays commonly used to define new nozzles. However, considering the power of the available computers, the use of wall models is a necessary step to simulate full scale devices. With this framework, one presents a set of direct numerical simulations whose analysis allows to derive new wall functions integrating several complex physical aspects that modify the "classical'' behavior of the turbulent boundary layer: multicomponent reacting compressible flow, with non-unity Prandtl number, radiative transfer, streamwise pressure gradient, and wall ablation. These new models are now ready to be tested on realistic configurations.

P. Comte	Professor - ENSMA, Poitiers	Referee
P. Sagaut	Professor - University of Pierre et Marie Curie, Paris VI	Referee
J. Couzi	Engineer researcher - CEA/CESTA, Le Barp	Member
J.M. Déoclézian	Engineer - Snecma Propulsion Solide, Haillan	Member
B. Mohammadi	Professor - University Montpellier II	Member
M. Stanislas	Professor - Ecole centrale, Lille	Member
F. Nicoud	Professor - University of Montpellier II	Advisor