Numerical investigations of interface instability and turbulent mixing driven by implosion

The interface instability and turbulent mixing of perturbed Air/SF6 interface driven by implosion in spherical convergent geometry are numerically investigated by the use of in-house compressible hydrodynamic code (multi-viscous flow and turbulence). The results revealed the complex evolving laws and physical mechanisms of interface instability and turbulent mixing due to the evolution of complex waves in this case. The RM instability is induced when the perturbed Air/SF6 interface is driven by the incident shock wave. And the perturbed interface accelerates toward the center, thereafter RT instability occurs. Then the perturbed interface slows down and decelerates towards the center, and the RT stabilization appears and suppresses the development of the interface instability and turbulent mixing. When the RT stabilization acts an absolutely dominant role, the growth of the turbulent mixing zone (TMZ) width is restrained completely, and its width in turn reduces. After the rebound of transmitted shock waves, the secondary loading from heavy fluid to light fluid is a combination of quasi-isentropic ramp wave, shock wave and Taylor wave in time series. The loading of quasi-isentropic ramp wave also contributes to the RT stabilization mechanism, the drive of rebound shock wave was seen to have induced the RM instability too, and the impact of Taylor wave resulted in RT instability once again. In the following, the reflected wave moves toward the center and bounces, the third loading process is the same as the secondary one; the TMZ width repeats the same growth laws. The Bell-Plesset (BP) effect which belongs to the conergent geometry can promote the development of TMZ. In the spherical converegent geometry, the competition mechanism among the RM instability, RT instability, BP effect and RT stabilization controls the evolution of interface instability and turbulent mixing. The distributions of turbulent kinetic energy indicate that TMZ evolves asymmetrically along the radial direction. The distributions of three direction components of turbulent kinetic energy and energy spectra also exhibit the evolution of TMZ as strong anisotropy.