Nonlinear evolution of an interface in the Richtmyer-Meshkov instability.

Area of Science:

• Fluid dynamics
• Plasma physics
• Instability phenomena

Background:

• The linear theory of Richtmyer-Meshkov instability attributes it to velocity shear from rippled shocks.
• Previous models did not fully capture nonlinear effects at a corrugated interface.

Purpose of the Study:

• To investigate the nonlinear evolution of the Richtmyer-Meshkov instability.
• To analyze the self-interaction of a nonuniform vortex sheet with a density jump.

Main Methods:

• Developed a nonlinear theory for interface evolution.
• Utilized Lagrangian markers to track interface deformation.
• Analyzed vorticity dynamics and interface stretching/shrinking.

Main Results:

• Finite density jumps and corrugation amplitudes significantly impact instability.
• Vorticity is not conserved in the nonlinear regime, leading to spiral spike structures.
• Nonlinear growth depends on initial corrugation, Atwood number, and shock intensity.

Conclusions:

• The developed nonlinear theory accurately predicts instability evolution.
• Results align with experimental observations.
• Provides a comprehensive understanding of nonlinear Richtmyer-Meshkov instability dynamics.