Collaborative Research: Probing Cavitation Inception in Dielectric Liquids with Sub-Nanosecond Precision

合作研究：以亚纳秒精度探测介电液体中的空化起始

• 批准号: 2129400
• 负责人: Mikhail Shneider
• 金额: $ 27.1万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-12-15 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2129400&HistoricalAwards=false
• 关键词: Collaborative; Research; Probing; Cavitation; Inception

Cavitation is the formation of bubbles (or cavities) in liquids due to decreased pressure. Accurate determination of the critical conditions of cavitation is of fundamental interests to many technological fields such as fluid machinery design and targeted drug delivery. So far, the experimental results of cavitation threshold pressures have not been consistent. One prominent factor is that the existing techniques cannot reliably capture the very early stage of cavitation inception. Recent works have shown that nanoscale cavities can form in dielectric liquids due to negative pressure generated by nanosecond-pulsed electric fields. Since this process can be synchronized and controlled electrically (which is not the case for existing methods), it hints at a novel technique to “pinpoint” cavitation inception with sub-nanosecond precision in time and therefore enable a more accurate determination of cavitation thresholds. This research project will explore the potential of the proposed method and use it to measure the cavitation thresholds of water and other liquids, which would be very valuable for the validation of cavitation theories and models. This interdisciplinary research will have substantial educational outputs, with an emphasis on innovative approaches to STEM enrichment for underrepresented minority students. The PIs will develop and deliver new learning modules on topics related to the research, such as electrical discharges and fluid mechanics in everyday life. The objective of this project is to experimentally characterize the initial stages of electrostrictive cavitation in simple dielectric liquids as well as liquids with dispersed particles and theoretically elucidate underlying physical processes at the sub-ns timescale. As relevant theoretical analyses have been limited to oversimplified scenarios and experimental evidence is rare and far from systematic, the approach to accomplish the objective is through synergistic use of diagnostic measurements at different developmental stages and numerical modeling of the actual experimental scenarios. The research plan has two specific aims: (1) detection of cavitation initiation in liquids under ultra-short pulsed electric fields; and (2) examination of the effects of the dispersed phase in liquids on cavitation. Optical diagnostics including Schlieren/shadowgraph, Rayleigh scattering, and speckle imaging, combined with electrical and material characterization measurements, will be used to probe early-stage cavitation in various dielectric liquids, with and without dispersed particles, under different electrode geometries. For simple liquids such as water, the experimental data will be compared with the results from systematic numerical simulations to determine the critical conditions of cavitation initiation. For two-phase dispersions, the correlations between the experimental conditions and optical diagnostic results will be established, which will provide the information for the analysis and modeling of electrostrictive cavitation near dispersed particles, and by doing so, deepen the understanding of the physical processes involved. The expected outcomes of the research will include the determination of critical parameters for cavitation initiation in various liquids and a delineation of the physical picture of the subsequent developments of cavitation and the effects of the dispersed phase. This project will bridge the knowledge gap of cavitation initiation at sub-nanosecond timescale and be instrumental in advancing the technologies related to cavitation as well as nanosecond/sub-nanosecond plasma discharge in liquids.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.

空化是由于压力降低而在液体中形成气泡（或空腔）。准确确定空化临界条件对于流体机械设计、靶向给药等领域具有重要意义。到目前为止，空化阈值压力的实验结果还不一致。一个突出的因素是，现有的技术不能可靠地捕获非常早期的空化初生阶段。最近的工作表明，由于纳秒脉冲电场产生的负压，可以在介电液体中形成纳米级空腔。由于该过程可以被同步和电控制（这不是现有方法的情况），因此它暗示了一种新的技术，以在时间上具有亚纳秒精度的“精确定位”空化起始，因此能够更准确地确定空化阈值。本研究项目将探索所提出的方法的潜力，并使用它来测量水和其他液体的空化阈值，这将是非常有价值的空化理论和模型的验证。这项跨学科研究将产生大量的教育成果，重点是为代表性不足的少数民族学生提供STEM丰富的创新方法。PI将开发和提供与研究相关的主题的新学习模块，例如日常生活中的放电和流体力学。本项目的目标是实验表征简单介电液体以及分散颗粒的液体中的电致伸缩空化的初始阶段，并从理论上阐明在亚纳秒时间尺度下的基本物理过程。由于相关的理论分析仅限于过于简化的情景，实验证据很少，而且远不系统，因此实现这一目标的方法是通过协同使用不同发展阶段的诊断测量和实际实验情景的数值模拟。该研究计划有两个具体目标：（1）在超短脉冲电场下检测液体中的空化起始;（2）检查液体中分散相对空化的影响。光学诊断，包括纹影/阴影，瑞利散射，和斑点成像，结合电气和材料表征测量，将被用来探测早期阶段的各种电介质液体中的空化，有和没有分散的颗粒，在不同的电极几何形状。对于简单的液体，如水，实验数据将与系统的数值模拟结果进行比较，以确定空化起始的临界条件。对于两相分散体，将建立实验条件和光学诊断结果之间的相关性，这将为分散颗粒附近的电致伸缩空化的分析和建模提供信息，并通过这样做，加深对所涉及的物理过程的理解。研究的预期成果将包括确定各种液体中空化起始的关键参数，并描绘空化随后发展的物理图像和分散相的影响。该项目将弥合亚纳秒时间尺度空化起始的知识差距，并有助于推进与空化以及纳秒/亚纳秒液体等离子体放电相关的技术。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。