On-demand emulsions from oscillatory two-phase shear flows

通过液-液界面的溶剂萃取是一种限制扩散的过程，它依赖于一相在另一相中的分散，以最大限度地提高相之间的表面积，例如PUREX过程中的核燃料纯化。类似地，液-液体系中的化学反应动力学，例如芳烃的硝化反应，是由生成界面面积的速率控制的。通常采用表面活性剂稳定的两相乳化来分散它们。然而，这造成了工业设计的挑战，因为在这个过程中增加了快速相分离的要求。该项目旨在提出一种纯流体力学方法，通过外力生成按需无稳定剂的乳液，当外力中断时，乳液会迅速返回分离相。具体目标有三个：a)描述依赖于惯性、粘性和表面张力之间竞争的基本界面破裂机制；B)根据流体性质和振动参数定制乳液性质；C)利用流体机械装置优化按需溶剂萃取。我们将使用定量实验和晶格玻尔兹曼（LB）模拟相结合的方法来深入了解界面破裂，重点是推导两层振荡剪切流中界面破裂的简单模型(目标（a)和(b)）。在这里，我们将进一步描述两相系统中的界面破裂，其中一种流体表现出非牛顿性质。然后，我们转向溶剂萃取的实验室模型的开发，并提供我们系统的概念验证，并根据振动状态评估其效率（目标(c)）。拟议的项目不仅将促进对牛顿流体和复杂流体中界面破裂的基本理解，而且可能为工业扩散限制过程提供新的设计解决方案。

Solvent extraction across a liquid-liquid interface is a diffusion-limited process that relies on the dispersion of one phase in the other to maximise the surface area between the phases, e.g., the purification of nuclear fuel in the PUREX process. Similarly, chemical reaction kinetics in liquid liquid systems, e.g., nitration of aromatics, are controlled by the rate of generation interfacial area. Surfactant-stabilized emulsification of the two phases is routinely used to disperse them. However, this creates industrial design challenges because of the added requirement of rapid phase separation following the process. The project aims to propose a purely hydrodynamic method to generate on-demand stabilizer-free emulsions through external forcing, which rapidly return to separated phases upon interruption of the forcing.The specific objectives are threefold: a) characterize the fundamental interface breakup mechanism which relies on competition between inertial, viscous, and surface tension forces; b) tailor emulsion properties depending on the fluid properties and vibrational parameters; c) use the fluid mechanical device to optimize on-demand solvent extraction. We will use a combined approach of quantitative experiments and Lattice-Boltzmann (LB) simulations to gain insights into interface breakup with a focus on deriving simple models for interface breakup in two-layer oscillatory shear flows (objective (a) & (b)). Herein we will additionally characterize interface breakup in two-phase systems where one fluid exhibits non-Newtonian properties. We then turn to the development of a laboratory model of solvent extraction and provide a proof-of-concept of our system and evaluate its efficiency depending on the vibrational regime (objective (c)). The proposed project will not only advance fundamental understanding of interface breakup in both Newtonian and complex fluids but also potentially offer new design solutions for industrial diffusion-limited processes.