The 4th International Conference on Matter and Radiation at Extremes (ICMRE 2019)

515 / 2019-03-19 15:09:20

Interaction of Cylindrical Shock with Heavy Gas Layer with Perturbed Inner Surface

RM instability,Convergent geometry

Plenary track > Interface Instabilities at Extremes

The Richtmyer-Meshkov instability (RMI) arises when an interface with perturbations between two different fluids is impacted by a shock wave. Previous investigations are limited to the case of an isolated interface interacting with a shock wave. For the RMI in realities such as ICF, one of the most concerned practical applications, there usually exist two interfaces separating three material shells. When the capsule is irradiated by an x-ray or laser, the imploding inner and outer interfaces with initial perturbations develop simultaneously. The co-evolution of two nearby interfaces exhibits a much more complicated instability development process than that of the single-interface case due to the addition of new physical mechanisms. Moreover, for a light/heavy case the perturbation amplitude increases quickly after the shock, while for a heavy/light interface the perturbation first undergoes a phase inversion before the growth.
In this work, the RMI on various special-shaped SF6 layers (uniform outer surface and sinusoidal inner surface) with different thickness subjected to a cylindrical shock wave is experimentally investigated in a semi-annular shock tube. The gas layers are generated by an improved soap-film technique and the shapes of the inner and outer boundaries as well as the layer thickness can be precisely controlled. Three SF6 layers with different amplitude-wavelength ratios and thickness are formed to highlight the effects of initial conditions. Detailed processes of the shock propagation and interface deformation are well captured by a high-speed schlieren photography, as shown in figure 1. The instability growth of the inner interface can be largely suppressed by reducing the layer thickness due to the inverse effects of the unperturbed transmitted shock and the interface coupling. Especially, for the largest thickness (Case 3), the development process of the gas layer is nearly similar to that of an isolated interface.