Abstract: The self-excited oscillating pulsed jet apparatus has attracted considerable attention due to its simple structure, ability to generate passive oscillatory cavitation, and ease of engineering application. Nevertheless, the majority of extant studies on self-excited oscillating pulsed jets focus on homogeneous water-based media, while research on the flow and mixing characteristics of multiphase media remains relatively scarce. This limitation hinders its application in enhancing liquid-liquid heterogeneous phase mixing processes. To elucidate the mixing mechanism of oil-water heterogeneous media in the jet apparatus, this study employs oil as the continuous phase and water as the dispersed phase. Numerical simulations were conducted using the realizable k-ε turbulence model, Euler multiphase flow model, and population balance model (PBM), with simulation accuracy validated through experiments. Based on this, the mixing process of oil-water heterogeneous media inside the jet apparatus and the droplet size distribution characteristics of the dispersed phase were simulated and analyzed. The results indicated that oil-water heterogeneous media generated cavitation bubbles with size periodic variations and pulsating cavitation jets inside the jet apparatus. Under the synergistic action of turbulent inertial forces and viscous shear forces, dispersed-phase droplets were broken up, thereby promoting the mixing of the oil and water phases. Further analysis revealed significant differences in the primary regions where turbulent inertial forces and viscous shear forces acted within the jet apparatus. Turbulent inertial forces were mainly concentrated near the outlet and inlet of the resonator cavity, facilitating fluid mixing in this region, whereas viscous shear forces mainly produced near the collision wall of the resonator cavity and the lower nozzle channel wall, enhancing the mixing process in these areas. The combined effect of turbulent inertial forces and viscous shear forces led to the continuous breakup of dispersed-phase droplets, effectively intensifying the mixing process of oil-water heterogeneous media. In addition, mixing by jet apparatus can obtain narrowly-distributed dispersed-phase (water) droplets.

Key words: self-exciting oscillation pulsed jet, heterogeneous fluid, mixing, cavitation, numerical simulation

摘要： 自激振荡脉冲射流器因结构简单、可产生无源振荡空化，且易于实现工程化应用而备受关注。但是，目前该射流器的研究对象以均相水介质体系为主，对于多相介质流动与混合特性的研究匮乏，这限制了其在强化液-液非均相介质混合过程中的应用。本工作以油为连续相，水为分散相，采用数值模拟结合实验研究的方法，模拟了油-水非均相介质在射流器内的混合过程及分散相液(水)滴直径分布。结果表明，油-水非均相介质在射流器内能够产生脉冲空化射流及大小周期性变化的空化泡；谐振腔出/入口附近流体受湍流惯性力作用最强，混合效果最好；相较于蓄能状态，释能状态下谐振腔室内非均相流体受黏性剪切力作用更强，更有利于油-水两相间混合；湍流惯性力与黏性剪切力共同作用，促进了分散相液(水)滴破碎，强化了油-水非均相介质间的混合过程；射流器的混合作用可获得液(水)滴尺寸分布窄的分散相。

关键词: 自激振荡脉冲射流, 非均相流体, 混合, 空化, 数值模拟