Pandey Deepak K, Kumar Rupak, Ranade Vivek V
Multiphase Reactors and Intensification Group, Bernal Institute, University of Limerick, Limerick V94T9PX, Ireland.
Multiphase Reactors and Intensification Group, Bernal Institute, University of Limerick, Limerick V94T9PX, Ireland.
Ultrason Sonochem. 2025 Sep;120:107493. doi: 10.1016/j.ultsonch.2025.107493. Epub 2025 Aug 5.
Hydrodynamic cavitation is increasingly used for the production of liquid-liquid emulsions, yet the detailed mechanisms of droplet breakup induced by cavity collapse remain poorly understood. This study presents direct numerical simulations (DNS) of oil droplet fragmentation under the influence of two symmetrically collapsing cavities in water, mimicking conditions in cavitation-based emulsification devices. A volume-of-fluid (VOF) multiphase model is employed to examine the effects of interfacial tension (σ), viscosity ratio (λ), droplet-to-cavity size ratio (β), and driving pressure (ΔP) on droplet deformation and energy dissipation rate (ε). Unlike prior studies focused on single-cavity interactions or turbulent flows, this work reveals that symmetric cavity collapse generates complex, multi-phase breakup dynamics involving vortex-induced deformation and secondary droplet formation. Results indicate that ε increases with an increase in β, σ and ΔP, whereas higher values of λ result in a decrease in ε. The dimensionless droplet perimeter (P/P) was found to vary exponentially with the key parameters. The dimensionless perimeter of the droplet at the time of breakup (P) decreases with an increase in σ, λ, ΔP and increases with β. A quantitative relationship is proposed between energy dissipation rate (ε), key parameters and dimensionless numbers (Weber and Ohnesorge numbers), identifying driving pressure and interfacial tension as dominant contributors. These insights enhance the mechanistic understanding of cavitation-driven emulsification and offer a foundation for optimising droplet size control and energy efficiency in industrial cavitation systems.
水力空化越来越多地用于液 - 液乳液的制备，然而，空化泡溃灭引起液滴破碎的详细机制仍不清楚。本研究进行了直接数值模拟（DNS），模拟基于空化的乳化装置中的条件，研究了水中两个对称溃灭的空化泡作用下油滴的破碎情况。采用流体体积（VOF）多相模型来研究界面张力（σ）、粘度比（λ）、液滴与空化泡尺寸比（β）和驱动压力（ΔP）对液滴变形和能量耗散率（ε）的影响。与之前关注单空化泡相互作用或湍流的研究不同，本研究表明对称空化泡溃灭会产生复杂的多相破碎动力学，包括涡旋诱导变形和二次液滴形成。结果表明，ε随β、σ和ΔP的增加而增加，而较高的λ值会导致ε降低。发现无量纲液滴周长（P/P）随关键参数呈指数变化。破碎时液滴的无量纲周长（P）随σ、λ、ΔP的增加而减小，随β的增加而增大。提出了能量耗散率（ε）、关键参数和无量纲数（韦伯数和奥内佐格数）之间的定量关系，确定驱动压力和界面张力是主要影响因素。这些见解增强了对空化驱动乳化的机理理解，并为优化工业空化系统中的液滴尺寸控制和能量效率提供了基础。
