CAREER: Consistent Continuum Formulation and Robust Numerical Modeling of Non-Isothermal Phase Changing Multiphase Flows

相变问题的数值模拟对于理解许多自然和工程过程至关重要。例如，造冰和增材制造。一个主要的挑战来自传热和流体动力学方程的耦合。水、聚合物和金属在熔化或蒸发等过程中都表现出变化，这也必须在模型中考虑。虽然在一些相变过程的建模方面已经取得了一些进展，但是同时熔融、凝固、蒸发和冷凝（MSEC）的气液固三相流动的建模仍然是一个未解决的问题。在这个项目中，研究人员将制定一个强大的数值方案来模拟可以同时经历MSEC和体积收缩/膨胀的三相气-液-固流动。该方法将允许对新兴制造技术（如增材制造和薄膜沉积）进行现实模拟和优化，其中所有四种模式的相变同时发生。此外，该项目还提供了重要的教育活动，包括在科学和高性能计算方面培训学生、拓展活动以及通过开源软件共享研究代码。本项目将开发具有相变的多相气液固流动的控制方程，该方程在连续和离散水平上都是一致的。该项目的重点是确保数值方案的稳定性，当所有四种模式的相变存在。它对于体积变化显著和高密度对比的流动尤其重要。分析和实验验证也是这个项目的一部分。为了验证数值格式能够捕捉到相变过程中密度/体积的变化，提出了一种新的解析模型。该框架将通过美国国家标准与技术研究所（NIST）关于金属凝固和蒸发的实验数据进一步验证。该项目将产生一个经过实验验证的框架，这将有助于模拟和理解金属增材制造工艺，如选择性激光熔化和粉末床熔化。先进的计算机模拟将允许制造业优化工艺参数，如激光扫描速度和气体流速，以确保高质量和无缺陷的打印部件。该项目的数值方法将通过IBAMR软件公开源代码，并提供用户友好的文档。为了提高学生对计算机的参与度，研究人员将提供：(1)应用科学计算的新项目课程；(2)与圣地亚哥的高性能计算行业合作，组织高性能计算（HPC）夏季研讨会；(3)与SDSU项目合作，从当地高中和社区大学招收学生，提供暑期实习机会。该奖项反映了美国国家科学基金会的法定使命，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。

Numerical modeling of phase change problems is crucial to understanding many natural and engineering processes. For example, ice formation and additive manufacturing. A major challenge arises from the coupling of heat transfer and fluid dynamics equations. Water, polymers, and metals all exhibit changes during processes like melting or evaporation that must also be considered in the model. Although several advances have been made in modeling some phase change processes, the modeling of three phase gas-liquid-solid flows with simultaneous melting, solidification, evaporation, and condensation (MSEC) remains an unsolved problem. In this project, the researchers will formulate a robust numerical scheme for simulating three-phase gas-liquid-solid flows that can undergo simultaneous MSEC and volume shrinkage/expansion. This method would permit realistic simulations and optimization of emerging manufacturing technologies like additive manufacturing and thin film deposition, where all four modes of phase change occur simultaneously. Additionally, the project provides significant educational activities, including training students in scientific and high-performance computing, outreach activities, and sharing of research codes through open-source software.This project will develop governing equations for multi-phase gas-liquid-solid flows with phase change that are consistent both at the continuous and discrete levels. The project focuses on ensuring the stability of the numerical scheme when all four modes of phase change are present. It is especially critical for flows with significant volumetric changes and with high-density contrast. Analytical and experimental validation are also part of this project. To validate that the numerical scheme captures the density/volume change during phase transition, a novel analytical model is proposed. The framework will be further validated with experimental data from the National Institute of Standards and Technology (NIST) on metal solidification and evaporation. This project will result in an experimentally validated framework that will assist in simulating and understanding metal additive manufacturing processes such as selective laser melting and powder bed fusion. Advanced computer simulations will allow the manufacturing industry to optimize process parameters, such as laser scan speed and gas flow rates, to ensure high-quality and defect-free printed parts. The numerical methods of this project will be made open source with user-friendly documentation via IBAMR software. In order to increase student participation in computing, the researcher will offer: (1) a new project-based course on Applied Scientific Computing; (2) organize summer workshops on high-performance computing (HPC) in partnership with the San Diego-based HPC industry; and (3) work with SDSU programs to recruit students from local high schools and community colleges to provide summer internship opportunities.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.