NUMERICAL SIMULATION STUDY ON THE FRAGMENTATION OF DIFFERENTLY SHAPED DROPLETS UNDER STRONG SHOCK WAVES

The deformation and breakup of fuel droplets play a critical role in scramjet engines, and understanding the breakup mechanisms induced by high-Mach-number shock–droplet interactions is of great engineering significance. In this work, a series of numerical simulations are carried out to investigate the interaction between shock waves and liquid droplets under high-Mach-number conditions (Ma > 3). A dissipative-interface compressible four-equation multiphase flow model is employed to describe the shock–droplet interaction process and the associated multiphase flow evolution. Droplets with different initial shapes, including spherical, disk-like, and olive-shaped configurations, are considered in the present simulations. The initial droplet geometry is quantitatively characterized by the aspect ratio and sphericity, so that the influence of non-spherical geometry on the shock-induced deformation and breakup process can be systematically examined. Based on these parameters, the evolution of shock-induced wave structures, interfacial deformation, and breakup behavior is analyzed in detail. To further elucidate the breakup modes occurring under high-Mach-number conditions, additional simulations are conducted for a standard spherical droplet. The numerical results indicate that, under the same high-Mach-number shock loading, both the complexity of interfacial evolution and the breakup intensity of non-spherical droplets are strongly dependent on the shock-facing aspect ratio and the degree of droplet elongation along the shock propagation direction. When the major axis of the droplet is parallel to the shock front, droplets with different initial shapes exhibit similar characteristics in their interfacial evolution. In contrast, when the major axis is oriented normal to the shock front, the olive-shaped droplet exhibits more pronounced volumetric accumulation and experiences the weakest breakup among all the configurations considered. Furthermore, our simulations at higher Mach numbers(Ma = 5,7,9,10) confirm the existence of a catastrophic shear-induced entrainment(SIE) breakup mechanism. The results demonstrate that a high Weber number is a necessary condition for the initiation and development of this breakup mode, providing a numerical foundation and relevant criteria for further investigations of shock–droplet interactions.