Distortion of a spherical gaseous interface accelerated by a plane shock wave

Area of Science:

• Fluid Dynamics
• Plasma Physics
• Instability Phenomena

Background:

• The Richtmyer-Meshkov instability is crucial in various physical phenomena, including astrophysics and inertial confinement fusion.
• Understanding the behavior of gaseous interfaces under shock acceleration is essential for predicting complex flow dynamics.
• Previous studies often focused on planar interfaces, necessitating research into spherical geometries.

Purpose of the Study:

• To investigate the evolution of a spherical gaseous interface accelerated by a plane weak shock wave.
• To analyze the influence of different initial density jumps (negative, near-zero, positive) on instability development.
• To experimentally determine the velocity and volume of vortical structures formed during the instability.

Main Methods:

• Experiments were conducted in a square cross-section shock tube.
• A multiple exposure shadowgraph diagnostic technique was employed for visualization.
• Spherical bubbles of helium, nitrogen, and krypton were introduced into air at atmospheric pressure.

Main Results:

• Significant differences in bubble distortion were observed for helium, nitrogen, and krypton bubbles.
• Experimental velocities and volumes of developed vortical structures were quantified.
• At late times, bubble velocities asymptotically approached constant values, aligning with theoretical predictions.

Conclusions:

• The initial density ratio across the interface strongly dictates the Richtmyer-Meshkov instability's behavior in spherical geometry.
• Vorticity and aerodynamic forces are the dominant factors influencing the motion and shape of the gaseous bubble under the studied conditions.
• Experimental findings provide valuable data for validating computational fluid dynamics models of shock-accelerated interfaces.