CAREER: Tuning liquid jet and splash dynamics by deformable and heterogeneous boundaries

液体在气体中流动的稳定性与药物输送、制造工艺和热管理有关。稳定性取决于流动流体的性质以及系统中固体的机械和表面性质。为了更好地了解这些系统中液体流动的稳定性，这个项目将研究固体的性质如何影响自由液体射流和水进入飞溅。具体地说，这项研究将介绍(I)响应流体运动而变形的软材料，以及(Ii)空气、液体和固相相遇处的空间非均匀固体润湿特性。喷流最令人感兴趣的特征是凝聚的液柱解体成液滴的长度。这里，这个长度将通过在孔口处采用可变形喷嘴和不均匀的表面化学(即润湿特性)来控制。在研究水进入时，固体冲击器溅射到液池中，由此产生的分散的液体和携带空气的空腔行为是令人感兴趣的。这样的飞溅特征将通过使用化学不均匀表面的固体弹丸和通过液体表面上的顺应性固体薄膜来改进。这些科学努力整合了教育活动，通过讲座、课堂流量控制实验、指导科学博览会项目和教师研究参与研讨会，让当地高中生和教育工作者参与到科学过程中来。动态三相接触线与软固体的耦合物理表征还处于初级阶段。这项研究致力于探索通过材料顺应性和表面处理来改变多相界面的流体流动。实验和理论将用于理解包括上述被动流动改进剂在内的射流稳定性的物理原理。对自由流动液体射流中初始扰动及其抑制的新认识将有助于将线性射流稳定性理论应用于可变形喷嘴。对具有柔顺介质的自由液面的修正和对具有非均质边界的固体弹丸的改变，将对入水的飞行器产生中等韦伯数的新的理论处理方法。因此，将重新定义空腔产生和坍塌的条件，并将探索非轴对称空腔产生升力的极限。实验技术包括捕捉流动特征的高速摄像技术，阐明运动学的数字跟踪技术，成像表面的显微技术，以及对研究中使用的固体表面进行化学表征的X射线光电子能谱。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The stability of liquids flowing through gas is relevant to drug delivery, fabrication processes, and thermal management. The stability depends on the properties of the flowing fluid and on the mechanical and surface properties of the solid bodies in the system. To better understand the stability of liquid flow in these systems, this project will study how the properties of solid bodies affect both free liquid jets and water entry splashes. Specifically, this research will introduce (i) soft materials that deform in response to fluid motion, and (ii) spatially nonuniform solid wetting properties where the air, liquid, and solid phases meet. The feature of greatest interest in jets is the length at which the coherent liquid column disintegrates into drops. Here, this length will be controlled by employing deformable nozzles and nonuniform surface chemistry (i.e. wetting properties) at the orifice. In studying water entry, a solid impactor splashes into a liquid pool, and the resulting dispersed liquid and air-entraining cavity behavior are of interest. Such splash features will be modified using both solid projectiles with chemically nonuniform surfaces and via compliant solid films atop the liquid surface. These scientific endeavors integrate educational activities that engage local high school students and educators in the scientific process through lectures, classroom flow control experiments, mentored science fair projects, and research engagement workshops for teachers.The characterization of the coupled physics of dynamic three-phase contact lines with soft solids is in its infancy. This research effort seeks to explore fluid flows where the multiphase interface has been modified via material compliance and surface treatments. Experiments and theory will be used to understand the physics of jet stability with the inclusion of the aforementioned passive flow modifiers. A new understanding of initial disturbances and their suppression within free stream liquid jets will inform the adaptation of linear jet stability theory for deformable nozzles. The modification of free liquid surfaces with compliant media and the alteration of solid projectiles with heterogeneous boundaries will produce new theoretical treatments at moderate Weber numbers for vehicles entering water. Thus, conditions for cavity creation and collapse will be redefined, and the limits of lift force production from non-axisymmetric cavities will be explored. Experimental techniques include high-speed videography to capture flow features, digital tracking to elucidate kinematics, microscopy to image surfaces, and X-ray photoelectron spectroscopy to chemically characterize the solid surfaces used in this study.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.