99 / 2023-04-13 21:00:54

Experimental development of turbulent mixing on Shenguang laser facilities

Richtmyer-Meshkov instability, Rayleigh-Taylor instability, Reshock, Convergent geometry, Turbulent mixing

辐射和流体力学 > 高能量密度科学与温稠密物质-II

    In inertial confinement fusion, hydrodynamic instabilities play a central role in the performance degradation of implosions. These instabilities bring the mix between the cold shell and the hot core. The mix caused by reshock is an important problem in astrophysics and deflagration-to-detonation transition. Better understanding of the turbulent mixing process is not only beneficial to the control of the development of the hydrodynamic instabilities, but also can be used to test mix models.

    A series of reshock experiments using planar target are conducted on Shenguang laser facilities to study the physical process of deeply nonlinear regime and turbulent mixing. The experiments uses laser to drive the two sides of shock tube to produce counter-propagating shocks, the interface evolves by action of Richtmyer-Meshkov (RM) instability growth and its subsequent reshock, compression, and re-growth phases. The growth is imaged with backlit x-ray radiography. The obtained mix width provide a one-dimensional information to validate the mix models, and the time evolution of density distribution can give more information to visualize and qualitatively describe the reshock process. For instance, the density field can be used to visualize the fine structure of perturbation interface and provide two-dimensional information to improve the confidence of mix models.

    Convergent geometry introduces effects not present in planar geometry such as shell thickening and growth caused purely by geometry due to the Bell-Plesset effect. Experiments have been done to investigate the effects of convergence on RM growth and Rayleigh-Taylor (RT) growth of decelerated regime. Side-on x-ray radiography is used to measure instability growth occurring between the inner surface of aluminium and plastic foam from well-characterized perturbation. The growth of decelerated regime RT instability is observed, as well as the feedout from inner surface of aluminum to the outer surface of the cylinder. Numerical simulations are in good agreement with experimental results.