High-amplitude single-mode perturbation evolution at the Richtmyer-Meshkov instability

Area of Science:

• Fluid Dynamics
• Hydrodynamic Instabilities
• Shock Wave Physics

Background:

• The Richtmyer-Meshkov instability (RMI) is a fundamental phenomenon in fluid dynamics, crucial for understanding mixing processes in various applications.
• Previous studies often focused on small-amplitude perturbations or specific interface types, necessitating further investigation into nonlinear regimes and diverse gas combinations.

Purpose of the Study:

• To experimentally investigate the single-mode Richtmyer-Meshkov hydrodynamic instability at different gas interfaces (light/heavy, close density, heavy/light).
• To analyze the nonlinear regime of RMI using high-amplitude initial perturbations and compare experimental growth rates with existing theoretical models.

Main Methods:

• Utilizing a shock tube to generate a low Mach number incident shock wave.
• Implementing two-dimensional, half-sinusoidal initial perturbations with high amplitude to induce nonlinear behavior.
• Conducting experiments with various gas pairs: air/SF6, air/CO2 (light/heavy), air/N2 (close density), and air/He (heavy/light).

Main Results:

• Growth rate measurements for air/SF6 and air/CO2 interfaces align well with a nonlinear model incorporating a reduction factor.
• The reversal phase in the air/N2 (close density) interface is accurately described by linear theory.
• The air/He (heavy/light) interface experiment is well-represented by a nonlinear model with a reduced factor.

Conclusions:

• The study validates nonlinear models for RMI under specific conditions, highlighting the importance of reduction factors for accurate predictions.
• Linear theory effectively describes the reversal phase for close-density interfaces.
• Experimental data provides valuable insights into the behavior of hydrodynamic instabilities across a range of density ratios.