The evolution of hydrodynamic instabilities under high-energy-density conditions in converging geometries represents a critical challenge in fields such as inertial confinement fusion (ICF) and astrophysics. While substantial research has been conducted on the linear and weakly nonlinear stages of Rayleigh-Taylor instability (RTI) evolution, significant gaps remain in understanding its strongly nonlinear phase. This study investigates the nonlinear evolution of RTI in cylindrical converging geometries. Our findings reveal that convergence effects primarily influence RTI evolution through perturbation wavelength modulation and background flow field interactions, distinguishing cylindrical RTI dynamics from planar configurations. By employing a perturbation decomposition method, we establish a theoretical model capable of predicting the nonlinear evolution of spikes and bubbles. This model has been validated through recent ICF experiments and successfully explains observed discrepancies between experimental measurements and numerical simulations.

Rayleigh-Taylor Instability,Converging Cylindrical Geometry