The dynamics of ultrafast cold cavitation in liquids

液体中超快冷空化的动力学

• 批准号: 2123634
• 负责人: Claudiu Stan
• 金额: $ 46.04万
• 依托单位: Rutgers University Newark
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-03-01 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2123634&HistoricalAwards=false
• 关键词: dynamics; ultrafast; cold; cavitation; liquids

Phase transitions, such as evaporation or boiling, involve molecular mechanisms that are well understood when the transition occurs slowly. However, in many natural phenomena and technological processes, phase transitions occur very rapidly. An important example is cavitation, which is the formation of bubbles due to low or even negative pressures in liquids. Cavitation starts with the nucleation and rapid growth of bubbles. The process is difficult to characterize in three-dimensional samples because it can occur anywhere and is completed in nanoseconds. Classical nucleation theory (CNT) helps understand the dynamics of nucleation, but there are important cases where it fails, such as cavitation in pure water near room temperature, which occurs at very different pressures than those predicted by CNT. Refining theoretical models requires accurate experimental data. Furthermore, data under extreme conditions is important for addressing cavitation in applications such as modern diesel engines, which use high pressure fuel injection to achieve high efficiency and low emissions. This project will apply and refine laser ablation techniques to induce cavitation at large negative pressures on nanosecond time scales, and ultrafast flashes of light and X-rays to capture the evolution of cavitation bubbles over nanoseconds and at nanometer dimensions. Advanced image analysis and computational fluid dynamics (CFD) simulations will be used to increase the accuracy of pressure measurements at the inception of cavitation. The work will be performed in university labs and at X-ray free-electron laser (XFEL) facilities and will involve a collaboration on CFD simulations with Prof. Dr. Nikolaus Adams at the Technical University of Munich. The project will train graduate and undergraduate students and will expose them to university research and also to large science facilities and international collaborations.The project will investigate cavitation in water and diesel fuel below the boiling point (cold cavitation) at time and length scales that represent the experimental frontier of the field (nanosecond and nanometer, or “ultrafast”), using pulsed X-ray laser ablation and pulsed optical ablation. The techniques to induce cavitation at the nanosecond-nanometer scales have been recently demonstrated, but they must be refined, and high accuracy measurements of cavitation pressures and nucleation rates are not yet possible. Therefore, new techniques will be developed to characterize the dynamics of ultrafast cavitation: (1) extracting directly from high-accuracy optical images of drops and jets detailed hydrodynamic parameters, such as pressure wave kinematics and amplitude, using advanced image analysis in combination with image simulations; (2) combining high-accuracy image data with high-accuracy computational fluid dynamics (CFD) simulations to measure very high cavitation rates as a function of pressure; and (3) imaging rapidly evolving nanobubbles using femtosecond X-ray laser scattering. Additionally, liquid jet ablation experiments will be designed and used to quantify a poorly understood type of cavitation that occurs in pure water.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.

相变，如蒸发或沸腾，涉及分子机制，当过渡缓慢发生时，这些机制已经被很好地理解。然而，在许多自然现象和技术过程中，相变发生得非常快。一个重要的例子是空化，这是由于液体中的低压甚至负压而形成的气泡。空化开始于气泡的成核和快速增长。 这个过程很难在三维样品中表征，因为它可以在任何地方发生，并且在纳秒内完成。经典成核理论（CNT）有助于理解成核的动力学，但也有一些重要的情况下，它失败了，如在接近室温的纯水中的空化，这发生在非常不同的压力比CNT预测。完善理论模型需要精确的实验数据。 此外，极端条件下的数据对于解决现代柴油发动机等应用中的气穴现象非常重要，这些柴油发动机使用高压燃料喷射来实现高效率和低排放。该项目将应用和改进激光烧蚀技术，在纳秒时间尺度上在大负压下诱导空化，并利用超快闪光和X射线捕获纳秒和纳米尺度上空化气泡的演变。先进的图像分析和计算流体动力学（CFD）模拟将用于提高空化开始时压力测量的准确性。 这项工作将在大学实验室和X射线自由电子激光（XFEL）设施中进行，并将与慕尼黑工业大学的尼古拉斯亚当斯教授合作进行CFD模拟。该项目将培训研究生和本科生，让他们接触大学研究、大型科学设施和国际合作。该项目将研究沸点以下的水和柴油中的空化现象（冷空化）在时间和长度尺度上代表了该领域的实验前沿（纳秒和纳米，或“超快”），使用脉冲X射线激光烧蚀和脉冲光学烧蚀。在纳秒-纳米尺度上诱导空化的技术最近已经被证明，但它们必须被改进，并且空化压力和成核率的高精度测量尚不可能。因此，将开发新的技术来表征超快空化的动力学：（1）直接从液滴和射流的高精度光学图像中提取详细的流体动力学参数，例如压力波运动学和振幅，使用先进的图像分析结合图像模拟;（2）将高精度图像数据与高精度计算流体动力学（CFD）模拟相结合，以测量作为压力的函数的非常高的空化率;以及（3）使用飞秒X射线激光散射对快速演化的纳米气泡进行成像。此外，液体射流烧蚀实验将被设计和用于量化一个鲜为人知的类型的空化发生在纯水中。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

项目成果

Microstructure and crystal order during freezing of supercooled water drops

过冷水滴冻结过程中的微观结构和晶序

• DOI: 10.1038/s41586-023-06283-2
• 发表时间: 2023
• 期刊: Nature
• 影响因子: 64.8
• 作者: Kalita, Armin;Mrozek-McCourt, Maximillian;Kaldawi, Thomas F.;Willmott, Philip R.;Loh, N. Duane;Marte, Sebastian;Sierra, Raymond G.;Laksmono, Hartawan;Koglin, Jason E.;Hayes, Matt J.
• 通讯作者: Hayes, Matt J.