It is of great importance for fields such as implosion dynamics and fusion research to understand the dynamics of ejecta transport in converging gases. In this paper, the evolution of particulate flow within a cylindrically imploding system is investigated experimentally and numerically. The ejecta particles are emitted from the inner surface of a roughened Sn liner into vacuum, He and Ar gases. Dynamic images of liner implosion and ejecta transport are obtained with X-ray radiographs and multi-frame optical schlieren images. The transport of ejecta particles is simulated with a four-way coupled multiphase flow model, including modelling of gas–particle coupling and inter-particle collisions. Results reveal that the ejecta transport in shock-induced converging gases differs significantly from that in planar systems, primarily due to features such as interaction with the rebounding gas shock wave and continuous compression by the imploding liner. After being generated from the inner surface, the ejecta width undergoes an ‘expansion–compression’ variation. According to mechanisms governing ejecta–gas coupling, three distinct stages of ejecta evolution are identified: (i) post-shock transport dominated by drag and particle breakup; (ii) shock-particle interaction leading to quick reduction in particle size and rapid deceleration of the ejecta front; and (iii) dense ejecta compression governed by inter-particle collisions. Leveraging particle motion and size predictions at the ejecta front, combined with the self-similar converging shock solution, a theoretical model is established to estimate the three-stage evolution of ejecta width in a cylindrically converging system.
Zhang et al. (Mon,) studied this question.