Bridging the gap in multiphase flow simulations

理解和预测多相流的动力学是很重要的，因为这些流动在日常生活和许多工程应用中都有发现。在自然界中，包含两个或更多阶段的流动包括云、沙尘暴和河流中的沉积物运输。燃料喷雾、治疗肺部感染和疾病的药物喷雾、气动输送、粉末加工和气泡塔反应器都是依赖于多相流的许多应用。与已建立的单相流方法不同，两相流的模拟更具挑战性，因为处理分离两相界面的不连续、质量和动量交换需要增加复杂性和成本。尽管几十年来计算能力不断增强，但最先进的多相流求解器的部署仍然仅限于精心策划和简化的学术流，而许多应用仍然遥不可及。该项目的目标是开发数字策略，保持高保真度，同时使用计算效率高的方法降低计算成本。这项研究将使许多经常进行多相流模拟的行业受益，从而为工程系统的设计提供信息。降低的计算成本将使以前无法进入的地区的真实流动模拟成为可能。该项目还旨在通过在亚利桑那州立大学数字增强表演艺术舞台的推广活动中提供的体验式学习模块，激励年轻的孩子们追求与流体力学相关的职业。研究生和本科生将通过参与研究获得更强的专业准备和培训。将研究一种新的计算方法，该方法可以在同一模拟中实现从完全解析到完全建模的界面动力学的一致和连续过渡。该方法以体积滤波理论为数学基础。该方法在精神上类似于大涡模拟方法，其中界面尺度大于滤波器宽度被完全解决，尺度小于滤波器宽度被完全建模。本文将对该方法的三种变体进行实现和表征：体积滤波浸入边界、体积滤波流体体积和体积滤波欧拉-拉格朗日。研究将揭示使用欧拉-拉格朗日方法允许从已解界面到模型界面的一致和保守过渡的精确条件，其中特征界面长度尺度降至滤波器尺寸以下。该方法将在雾化射流和载粒子通道流的模拟中得到验证。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。

Understanding and predicting the dynamics of multiphase flows is important as these flows are found in everyday life and in many engineering applications. In nature, flows that involve two phases or more include clouds, dust storms and sediment transport in rivers. Fuel sprays, pharmaceutical sprays to treat pulmonary infections and diseases, pneumatic transport, powder processing and bubble column reactors are among the many applications relying on multiphase flows. Unlike single-phase flows which have established methods, simulations of two-phase flows are far more challenging due to the added complexity and cost required to deal with discontinuities, mass and momentum exchange at the interface separating the two phases. Despite decades of growing computational power, deployment of state-of-the art multiphase flow solvers remains exclusive to well curated and simplified academic flows, while many applications remain out of reach. The goal of this project is to develop numerical strategies that retains high-fidelity yet reduces the computational cost using computationally efficient methods. This research will benefit a wide range of industries where multiphase flow simulations are routinely conducted to inform the design of engineering systems. The reduced computational cost will enable simulations of real-life flows in regimes previously inaccessible. The project also aims at inspiring young kids to pursue careers related to fluid mechanics through an experiential learning module delivered during an outreach event in a digitally-enhanced performance arts stage at Arizona State University. Graduate and undergraduate students will receive stronger professional preparation and training through involvement in research.A novel computational approach will be investigated, which enables a consistent and continuous transition from fully resolved to fully modeled interfacial dynamics within the same simulation. The method builds on the volume-filtering theory as its mathematical support. The approach is similar in spirit to the Large Eddy Simulation method where interface scales larger than the filter width are fully resolved, and scales smaller than the filter width are fully modeled. Three variants of the method will be implemented and characterized, Volume-Filtered Immersed Boundary, Volume-Filtered Volume of Fluid and Volume-Filtered Eulerian-Lagrangian. The investigation will reveal the precise conditions allowing consistent and conservative transition from resolved to modeled interface using the Eulerian-Lagrangian approach where the characteristic interface length scale drops below the filter size. The approach will be demonstrated in simulations of atomizing jets and particle-laden channel flow.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.