Impact of Fluid Rheology and Density Ratio in Droplet Collision: A Numerical Investigation

Abstract

This research delves into the intricate interplay of fluid rheology, characterized by the power-law model, and density ratio ρr=ρl/ρg in the context of droplet collision dynamics. The power-law index (n) is systematically varied within the range of 0.5–1.5, while the density ratio spans 2 orders of magnitude, ranging from 101 to 103. Comprehensive investigations are conducted across various impact parameters (B = 0–0.75) and Weber numbers (We = 40–160). A noteworthy finding is the cessation of droplet coalescence at elevated Weber numbers (We = 160), revealing a critical threshold beyond which coalescence is no longer sustained. The impact of fluid rheology on internal fluid flow dynamics within the complex droplet structure is substantial. The variation in viscous dissipation with (n) contributes to observable changes in the critical wavelength of the complex droplet rim structure, consequently influencing the size of child droplets. Furthermore, the density ratio is a pivotal factor influencing the deformation rate during collision events. A decrease in density ratio correlates with a reduction in the deformation ratio, shedding light on the significant role of density ratio in shaping the dynamics of droplet collisions.