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，冰的形成和增材制造。一个主要的挑战来自于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会发生变化，这也必须在模型中考虑。虽然在模拟某些相变过程方面取得了一些进展，但同时熔化、凝固、蒸发和冷凝（MSEC）的气-液-固三相流的模拟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，用于模拟三相气液固流，可以同时进行MSEC和体积收缩/膨胀。这种方法将允许逼真的模拟和优化新兴的制造技术，如增材制造和薄膜沉积，其中所有四种相变模式同时发生。此外，该项目还提供了重要的教育活动，包括对学生进行科学和高性能计算方面的培训、推广活动以及通过开放源代码软件共享研究代码。该项目将开发在连续和离散水平上一致的多相气-液-固相变控制方程。该项目的重点是确保稳定的数值方案时，所有四种模式的相变存在。对于具有显著体积变化和高密度对比度的流动，这一点尤其重要。分析和实验验证也是该项目的一部分。为了验证该数值计算方法能够准确反映相变过程中的密度/体积变化，提出了一种新的分析模型。该框架将进一步验证与实验数据从美国国家标准与技术研究所（NIST）的金属凝固和蒸发。该项目将产生一个经过实验验证的框架，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合。先进的计算机模拟将使制造业能够优化工艺参数，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软件开放源代码，并提供用户友好的文档。为了提高学生对计算的参与，研究人员将提供：（1）一个新的应用科学计算项目为基础的课程;（2）与圣地亚哥的高性能计算行业合作组织高性能计算（HPC）暑期工作坊;以及（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NSF的基金会的使命是履行其法定使命，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.