Numerical Investigations of Droplet Deformation and Breakup at Elevated Pressures

This work numerically analyzes the breakup (or secondary atomization) of a single Liquid Oxygen (LOX) droplet in uniform air and Helium crossflows. Transient Navier-Stokes solutions are obtained using the finite volume solver Basilisk over cartesian meshes. The droplet breakup regimes are explored with an incompressible all-Mach Navier- Stokes solution approach to investigate the effect of the density ratio and the pressure for LOX droplet breakup processes. Surface tension and viscous forces at the interface are considered in both cases. The projection method, which decouples momentum and pressure fields, employs a momentum-conserving algorithm. Droplet breakup simulation results of two-dimensional axisymmetric computations for different Weber numbers adjusted with the crossflow velocity at low Ohnesorge numbers are computed. A bag breakup regime is observed for lower We numbers and above We = 75, the shear breakup regime is observed. The breakup of LOX droplets is calculated at 101 and 1010 kPa ambient air pressure environments attained by varying air density and surface tension values. Earlier secondary breakup is shown at higher pressure conditions. Computations at 101 kPa are repeated for the Helium environment to investigate the density ratio effect between the liquid and gas phases. Two-dimensional droplet perimeter variations with normalized time curves show the difference of breakup processes at two density ratios.