(Georgia Institute of Technology, 2022-06-25)
Risley, Karl Robert
The current work investigates the behavior of gas curtain instabilities. A gas curtain
can be visualized as an A − B − A domain, where A and B are light and heavy fluids
respectively, creating a ”curtain” of heavy fluid B that is surrounded by a light fluid A.
Specifically, the behavior of gas curtains following an initial shock passage and the passage
of a reflected shock (reshock) through the entirety of the curtain are investigated. A
gas curtain instability commonly occurs physically in a wide range of applications such as
during afterburning of an explosion, inertial confinement fusion, and even supernovae explosions.
Previous studies have emphasized that the physics occurring during the reshock
of a gas curtain are far more complex than the behavior of a re-shock Richtmyer-Meshkov
Instability, due to the interactions between the two interfaces and wave reverberations occurring.
The current work attempts to understand the relationship between a gas curtain’s
initial conditions and its behavior to reshock through two-dimensional numerical simulations
that utilize the viscous Navier-Stokes equations. More specifically, the current work
isolates the effects of the curtain’s initial thickness and shape on the post reshock mixing
layer growth rate and molecular mixing of the curtain. The results for all cases indicate
that the post-reshock growth rate of the curtain’s width is a function of initial thickness.
The sensitivity of the curtain’s post-reshock growth rate to the initial thickness, however,
depends on the curtain’s initial perturbation shape. As the initial thickness of the curtain
is decreased, the interactions between the curtain’s interfaces grow in strength and impede
perturbation growth, thus reducing the post reshock growth rate of the curtain’s structure
width. Similarly, the results strongly suggest that a reduction in initial curtain thickness increases
the late-time asymptotic molecular mixing fraction value. This result is significant,
especially for reacting flows, because it indicates that faster combustion (or afterburning in
an explosion) could be reached with the thinning of the gas curtain in flow systems.