Simulation of drop deformation and breakup in supersonic flow

The deformation and breakup process of a liquid drop in supersonic flow is numerically studied with a coupled Level Set and Volume of Fluid method as the interface tracking approach. The Navier-Stokes equations in the liquid phase are solved by an incompressible flow solver using a finite volume method, and the governing equations in the gas phase are solved by a compressible flow solver using a finite difference method. Proper boundary conditions are specified at the interface for both liquid and gas flow solvers in order to correctly capture the interaction between the liquid and gas flows. It is demonstrated that the simulation cost can be significantly reduced by reducing liquid/gas density ratio while keeping the same Weber number and Ohnesorge number. Drop breakup at different Weber numbers is simulated. Bag breakup, bag stamen breakup, and multimode breakup modes are reproduced by the present two-phase flow solver. The physical mechanism for drop breakup in supersonic flow is investigated, and Rayleigh-Taylor instability is found to determine the breakup morphology for the studied Weber number range.