Investigating Turbulence Transition Metrics in NIF Shock-Tube Hydrodynamic Simulations

At the National Ignition Facility (NIF), a campaign of shock-tube experiments is being conducted to investigate the hydrodynamic growth of Rayleigh-Taylor (RT) and Richtmyer–Meshkov (RM) instabilities in nonlinear and pre-turbulent regimes at high-energy-density (HED) conditions. In parallel, this campaign is also enhancing diagnostic tools to achieve higher spatial resolution, enabling detailed visualization of fine-flow dynamics. By applying multiple shocks to the interface of a sufficiently optimized setup, we aim to observe the progression towards turbulence within the brief timeframe of a HED experiment. We present simulated data generated by the multi-physics code ARES overlaid with experimental effects to form synthetic radiograph images. We use Fourier analysis on repeating features within the Kelvin-Helmholtz instability whorls formed by the RT and RM perturbations to attempt differentiation between growth in the nonlinear regime (dominated by original wavelength harmonics) and the pre-turbulent regime (where initial wavelength conditions disappear). These results, coupled with future NIF experiments will help validate our large-eddy simulations of hydrodynamic instability development in mixing plasmas. 

  

Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-866059.