Weakly nonlinear ablative Rayleigh-Taylor instability at preheated ablation front

摘要

Stuart's weakly nonlinear theory is generalized to study single-mode ablative Rayleigh-Taylor instability (ARTI) at a broad ablation front caused by preheating. The thickness effect of the ablation front is considered and the spatial amplitude distributions of density, temperature, and velocity for harmonic modes are obtained in the present model. It is confirmed that the modified Lindl formula [W. H. Ye et al., Phys. Rev. E 65, 057401 (2002)] is valid for predicting the linear growth rate when the ablation front is broad. It is shown by the present model that the mass ablation of the shell is enhanced obviously due to the generation of harmonics while the harmonics' effect on the mass asymmetry of the shell is weaker than the expectation given by the classical theory. It is also indicated by the present model that ARTI is stabilized by the nonlinear correction for all modes. This conclusion is physical and different from the sharp boundary model where ARTI is enhanced by the nonlinear correction for the short wavelength case. The reason for this difference is due to the thickness effect of the ablation front.