Nonlinear mixing behavior of the three-dimensional Rayleigh–Taylor instability at a decelerating interface

Abstract

We report results from the first experiments to explore the evolution of the RayleighTaylor (RT) instability from intentionally three-dimensional (3D) initial conditions at an embedded, decelerating interface in a high-Reynolds-number flow. The experiments used 5 kJ of laser energy to produce a blast wave in polyimide and/or brominated plastic having an initial pressure of ~ 50 Mbars. This blast wave shocked and then decelerated the perturbed interface between first material and a lower-density, C foam. This caused the formation of a decelerating interface with an Atwood number ~2/3, producing a longterm positive growth rate for the RT instability. The initial perturbations were a 3D perturbation in an "egg-crate" pattern with feature spacings of 71 µm in two orthogonal directions and peak-to-valley amplitudes of 5 µm. The resulting RT spikes were observed to overtake the shock waves at the undisturbed, "free-fall" rate, and to subsequently deliver material from behind the interface to the forward shock. This result is unanticipated by prior simulations and models.

Annual Report 2006 for Hydrodynamics and Radiation Hydrodynamics with Astrophysical Applications

“…However, there are no 3D simulations of SN explosions, and the velocities remain too small to explain SN 1987A in 3D simulations 63,[73][74][75] and buoyancy-drag models 76,77 of isolated 3D spikes. Other existing studies of 3D RT instabilities, reviewed in Drake et al, 24 are of limited relevance for reasons discussed there.…”

“…These spikes were much longer that typical buoyancydrag models would predict. 24 It is quite clear that initial conditions determine how far the spikes penetrate. [This has also been seen in hydrodynamic simulations of planar systems in two dimensions.…”

“…Our experiments with specific three-dimensional initial conditions showed much larger transport than one would expect from the relevant simulations. 24 This important result led to improving our measurements and performing a sequence of experiments to explore specific variations in initial conditions. These efforts came to fruition in 2006, when we used dual-axis radiography with backlit pinholes and ungated detectors to obtain highresolution the physics data for a Ph.D. thesis, now under analysis.…”

Approaches to turbulence in high-energy-density experiments

“…Other extensive work has also been undertaken and is ongoing in the context of inertial fusion research. In addition, RT growth has been studied when a blast wave first shocks and then decelerates an embedded interface, in experiments motivated by supernova explosion dynamics [28][29][30][31]. In these cases, there is an initial RM response followed by a longer period of RT growth.…”

Stellar explosions, instabilities, and turbulence

“…This behavior has been explored in a sequence of experiments, marked by steadily increasing precision of the diagnostics and complexity of the structure. [49][50][51] The potential for surprises exists in the high-Reynolds-number regime of these flows, which cannot be fully simulated, especially if fluid turbulence develops as the structures evolve.…”