Reynolds number effects on the single-mode Richtmyer-Meshkov instability.

Area of Science:

• Fluid Dynamics
• Plasma Physics
• Astrophysical Instabilities

Background:

• The Richtmyer-Meshkov instability (RMI) is crucial in various physical phenomena, from inertial confinement fusion to astrophysics.
• Understanding the nonlinear growth of RMI is essential for predicting the behavior of complex fluid interfaces.
• Previous models have described RMI, but the specific influence of Reynolds number in the nonlinear regime requires further clarification.

Purpose of the Study:

• To investigate the effects of Reynolds number on the nonlinear growth rates of the Richtmyer-Meshkov instability.
• To identify the critical Reynolds number range where these effects become significant.
• To compare simulation results with existing theoretical models for RMI amplitude and velocity.

Main Methods:

• Two-dimensional numerical simulations were employed to model the RMI.
• Simulations were conducted across a range of Reynolds numbers to observe their impact.
• Bubble and spike amplitudes and velocities were tracked to quantify instability growth.

Main Results:

• A decrease in Reynolds number leads to a longer time to reach nonlinear saturation.
• Reynolds number effects are significant only for Re<256, showing a sharp change in instability properties.
• At lower Reynolds numbers, bubble and spike amplitudes tend to equalize, and bubble velocities decay faster than predicted by Sohn's model.

Conclusions:

• The Reynolds number plays a critical role in the nonlinear evolution of the Richtmyer-Meshkov instability.
• The simulations align well with theoretical predictions from Carles and Popinet, and Mikaelian, particularly the former.
• These findings provide valuable insights into RMI dynamics in regimes where viscous effects are important.