Formation Mechanism Of Jet-like Spike In Ablative Rayleigh-Taylor Instability In The Presence Of Preheating

Aiming at the actual requirement and the theory study in inertial confinement fusion and astrophysics, in this thesis we investigate the formation mechanism of jet-like spike in ablative Rayleigh-Taylor instability (RTI) in the presence of preheating by numerical simulation and theoretical analysis. The models of the RTI and the Kelvin-Helmholtz instability (KHI) for the linear growth rates with continuous profiles and for the weakly nonlinear mode coupling with discontinuous profiles are proposed. The mode coupling and the nonlinear evolution of the RTI and the KHI are studied numer-ically. The evolution of jet-like spike is divided physically into three stages according to the characteristics at different regimes. It is found that preheating plays an essential role on the formation of jet-like spike. The most important contribution of preheat-ing in the early stage is significantly increasing the density gradient stabilization of RTI and widening the velocity profile of the ablation front. In the middle stage, the combined effect of the thicknesses of density transition layer and velocity shear layer stabilizes dramatically the KHI. In the late stage, the nonlinear bubble acceleration further increases the jet’s length and finally leads to the formation of jet-like spike.