Evolution of turbulent mixing driven by implosion in spherical geometry

Abstract

The interface instability and turbulent mixing of perturbed multi-modes Air/SF6 interface driven by implosion in spherical geometry are numerically investigated. The results show the complex evolving laws and physical mechanisms of turbulent mixing. After the incident imploding shock, the transmitted shock wave moves towards the centre and bounces off outward to produce the second impact, which is a combination of reshock and Taylor wave rather than a single one like in planar case, and forms the loading/unloading effects. The following rebound impacts repeat this assembled loading/unloading process. In the whole process, the turbulent mixing zone (TMZ) growth is closely related to the multiple loading/unloading features. The Richtmyer-Meshkov instability (RMI), Rayleigh-Taylor instability (RTI), Rayleigh-Taylor stabilization (RTS) and Bell-Plesset (BP) effects coexist, and the competition mechanism results in the TMZ width growing in an oscillatory way. The statistics properties of TMZ are highly related to the multiple shocks process. The fluids mixing across TMZ is asymmetrical but behaves in a self-similar way. The evolution of TMZ has a high degree anisotropy, especially around the two edges of TMZ, the turbulent flow is also highly intermittent. When the turbulent mixing develops fully the energy spectra approach k -1 scaling law at the inertial subrange.