This study presents measurements of droplet transport inside a rotor-stator mixer under turbulent flow conditions and contributes to the understanding of the droplet breakup phenomenon. The measurements contain unique information on droplet breakup down to the limit of equilibrium droplet size. The experimental setup includes a custom-built rotor-stator mixer that provides optical access to the mixing region. High-speed camera imaging is used to study droplet stability and breakup due to turbulent inertial stress at different operating conditions. The analysis reveals when, where, and how the droplets break up inside the rotor-stator mixer. Analysis of the breakup location reveals that droplet breakup mainly occurs in the downstream region of the stator and inside the emanating jets. Prediction of the flow field and turbulent kinetic energy dissipation rate from CFD simulations explains the propensity of droplet breakup at different locations in the rotor-stator. It is found that both the average time for droplet-vortex interaction and the distribution increases with the size of mother droplets, and a model is proposed that explains the results fairly well. Measurement of the breakup probabilities reveals a monotonically increase from zero probability at a low We-number to approximately 50% probability at We > 4. The number of fragments formed upon breakage depend on how far the droplets are from equilibrium size and it is found that the probability for multiple fragmentation dominates even close to the equilibrium size.

中文翻译：

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转子-定子混合器中的单液滴破碎

这项研究展示了在湍流条件下转子 - 定子混合器内液滴传输的测量结果，有助于理解液滴破裂现象。测量包含有关液滴破碎到平衡液滴尺寸极限的独特信息。实验装置包括一个定制的转子 - 定子混合器，可提供对混合区域的光学访问。高速相机成像用于研究不同操作条件下由于湍流惯性应力引起的液滴稳定性和破裂。分析揭示了液滴在转子-定子混合器内何时、何地以及如何破裂。对破碎位置的分析表明，液滴破碎主要发生在定子的下游区域和喷出的射流内部。通过 CFD 模拟对流场和湍流动能耗散率的预测解释了转子-定子中不同位置的液滴破碎倾向。发现液滴-涡流相互作用的平均时间和分布都随着母液滴的大小而增加，并且提出了一个模型来很好地解释结果。破碎概率的测量显示从低 We 数的零概率单调增加到 We > 4 的大约 50% 的概率。 破碎时形成的碎片数量取决于液滴与平衡尺寸的距离，并且发现多次分裂的概率甚至在接近平衡大小时占主导地位。