Non-modal hydrodynamic stability analysis of ablation flows relative to inertial confinement fusion
Analyse non normale de stabilité hydrodynamique d'écoulements d'ablation en fusion par confinement inertiel
Résumé
A non-modal linear hydrodynamic stability analysis of ablation waves is carried out for the first
time. This analysis is performed for unsteady self-similar solutions in slab symmetry of the
Euler equations with nonlinear heat conduction, using a direct-adjoint method that results from
a Lagrangian-based optimization problem. Such solutions are considered in connection with
inertial confinement fusion (ICF) experiments where the hydrodynamic stability of ablative
flows has been identified as a key issue to the achievement of thermonuclear burn. Inherently
unsteady, these flows are compressible, highly nonuniform with a steep heat front, and bounded
by a material surface and a shock front — features that are possible sources of non-modal
thermo-acoustics effects. Non-modal effects are presently exhibited on a particular ablation wave
solution. This finding raises the question of the existence and consequences of such effects in
configurations of X-ray driven ablation that are more representative of ICF experiments, which
is the object of an ongoing investigation.
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