Microscale Self-Similarity Phenomenon of RM Instability on the Copper/Helium Interface with Molecular Dynamics Simulation

The Richtmyer-Meshkov instability (RMI) under extreme shock conditions has important academic and engineering significance in the field of inertial confinement fusion (ICF). Present macroscopic hydrodynamic methods are difficult to be directly applied to RMI in extreme conditions due to the lack of proper models and parameters in such states, while the microscopic results obtained by molecular dynamics (MD) are also difficult to be applied directly in macroscopic scale simulation due to computational cost. To understand the connection between macroscopic and microscopic RMI, the RMI evolution on copper-helium interface at different micro scales under different piston shock conditions (6–15 km/s) was simulated by the molecular dynamics method based on embedded-atom potential (EAM) models. Firstly, the RMI evolution obtained by MD was compared with available literature macroscopic results under similar conditions. Phenomenological similarity results between macroscopic and microscopic RMI is confirmed. The evolution histories of initial sinusoidal disturbance (amplitude/wave length ratio 0.20–0.05) at different incident shock wave speeds (11.7–20.6 km/s) and different scales (7.3–145.0 nm) from RMI simulations were further compared and analyzed. It is found that all amplitude evolution curves behave with self-similarity under same shock and boundary conditions, all main parameters vary in accordance with prediction of theoretical model. Although there exists some extent of discrepancy, similar amplitude evolution characteristics results are obtained by microscopic and macroscopic simulations.