NUMERICAL SIMULATION AND MECHANISM RESEARCH ON SHOCK/ELLIPTIC-LIQUID-COLUMN INTERACTION

The evolution of droplet morphology under shock impact is a classical problem in the study of compressible multiphase interfacial flows, with broad applications in numerous scientific and engineering fields. Since droplets in realistic flow fields are not strictly spherical, their initial deformation characteristics are incorporated into the present modelling framework, and the droplet is approximated as an ellipsoidal shape; correspondingly, in the two-dimensional configuration, it is represented as an elliptic liquid column. In this study, a diffuse-interface method based on a five-equation model is employed, and the two-dimensional Euler equations are solved to numerically investigate the interaction between a planar shock wave and an elliptic liquid column in a free-stream environment. Both prolate and oblate elliptical liquid columns subjected to weak and strong shock conditions are systematically investigated, with primary emphasis on the evolution of wave structures, interfacial deformation dynamics, and the development of characteristic flow features during the interaction process. The results indicate that, for both types of elliptical liquid columns, pronounced differences in wave structures arise primarily with increasing incident shock Mach number M_S. Regarding the deformation of prolate elliptical liquid columns, it is not only strongly affected by M_S, but also significantly influenced by the aspect ratio e. Variations of the two parameters lead to the identification of two distinct deformation modes: Mode I, primarily dominated by shear effects; Mode II, predominantly governed by impact effects. Furthermore, it is observed that the streamwise deformation rate of the liquid column is primarily governed by M_S, while showing a weak dependence on the aspect ratio e. In addition, the centroid velocity of the liquid column increases with decreasing e. The drag coefficient exhibits pronounced irregular oscillatory behaviour primarily due to vortex shedding in the wake region. Despite these fluctuations, its mean value remains approximately 0.9 during the early stage of interaction between the airflow and the liquid column.