CMG POST-DOC: Multiscale multiphase flow simulations of dense vesicular particle suspensions.

科学和工程中的许多流体（如下所列）都是囊状颗粒悬浮液，它们在散装流体流动和通过多孔介质时都表现出复杂的非牛顿流变性能。这种流体的复杂性是什么？流动行为不能用标准的Navier-Stokes方程来描述，它是变形过程中微尺度颗粒、气泡和液体相互作用的结果。将这些微观相互作用与由此产生的宏观行为联系起来的知识有限，限制了从（现场）观察推断流动过程的尝试，也限制了预测这些流体在自然环境或工程过程中的行为。因此，提出的研究目标是通过再现1)微观尺度上单个颗粒和气泡的相互作用，2)宏观尺度上具有代表性的基本体积行为，以及3)在实验室和现场尺度上更大的流体流动过程，对各种致密的囊状颗粒悬浮液的变形和流动进行数值模拟。这一目标将通过首先开发流体流动和悬浮包裹体（颗粒、气泡）运动的数值模拟器来实现，然后利用这些模拟以及热机械方法，推导出物理上可行的、大规模的连续力学模型，这些模型解释了微观尺度颗粒、气泡和液体相互作用的影响。模拟器将是一个混合的计算机代码，它结合了流体流动代码和模拟干燥颗粒材料中颗粒运动的代码。混合代码和派生的连续力学模型的预测能力将通过模拟材料和熔体实验以及可用的解析解进行测试。在科学和工程中，许多重要的流动现象是位于流体和固体之间的密集的囊状颗粒悬浮物（有时称为浆液）复杂流动行为的结果。涉及浆液的过程包括影响火山喷发动力学（爆炸性与喷涌性）的火山导管中的岩浆流动，以及影响火山灾害和可再生地热能源评估的热传递。其他地球科学应用包括滑坡、泥石流和火山泥流，它们也代表液体、颗粒和（有时）气泡的混合物，对地质灾害和（人为和自然）环境影响的评估具有重要意义。浆体的特定流动行为也在生物和医学过程中发挥重要作用，如血液通过静脉流动或地下水中的微生物运输。这个项目的工程应用可能包括食品、泡沫、水泥、凝胶和陶瓷加工。这里提出的研究旨在开发一种计算机代码来模拟颗粒和气泡在非常小的范围内的相互作用，以确定散装物质如何变形和流动以及它如何传导气体。在小尺度上获得的见解，然后扩大到实际的空间和时间尺度感兴趣。这种方法很困难，但很重要，因为包裹体（颗粒、气泡）的小规模相互作用对这些流体的复杂（非牛顿）流动行为有很大的影响，而通常引用的Navier-Stokes方程通常不能使用。因此，基于其包裹体特性来预测致密泥浆的流动行为，有可能对处理此类非标准但经常遇到且重要的流体的科学和工程产生重大影响。此外，该项目还支持一名博士后研究员，并通过实验室的互动，支持本科生和研究生接受数学、计算机、材料和地球物理科学的跨学科培训。开发的计算机代码有望引起许多科学和工程学科的兴趣。

Many fluids in science and engineering (listed below) are vesicular particle suspensions that exhibit complex non-Newtonian rheological behavior during both bulk fluid flow and during flow through porous media. The complexities of such fluids? flow behavior cannot be captured by standard Navier-Stokes equations and are the result of microscale particle, bubble, and liquid interactions during deformation. Limited knowledge connecting these microscale interactions to resultant macroscopic behavior restricts attempts to infer flow processes from (field) observations and to predict the behavior of these fluids in natural settings or in engineered processes. The objective of the proposed research is therefore to numerically model the deformation and flow of a variety of dense, vesicular particle suspensions by reproducing 1) individual particle and bubble interactions at the microscale, 2) representative elementary volume behavior at the macroscale, and 3) larger fluid flow processes on laboratory and field scales. This objective will be achieved by first developing a numerical simulator for fluid flow and suspended inclusion (particles, bubbles) motion, and then employing these simulations, as well as thermomechanical methods, to derive physically viable, large-scale continuum-mechanical models, that account for the effects of microscale particle, bubble, and liquid interactions. The simulator will be a hybrid computer code that combines a fluid flow code with a code to model the motion of particles in dry granular materials. The predictive capabilities of the hybrid code and the derived continuum-mechanical models will be tested against analogue material and remelt experiments as well as against analytic solutions where available.Many important flow phenomena in the sciences and in engineering are the result of the complicated flow behavior of dense, vesicular particle suspensions that lie in between fluids and solids, sometimes called slurries. Examples of processes that involve slurries include flow of magma in volcanic conduits affecting volcanic eruption dynamics (explosive versus effusive) and heat transfer with implications for the assessment of volcanic hazards and renewable geothermal energy resources. Other geoscience applications include landslides, mud flows, and lahars that also represent mixtures of liquids, particles, and (sometimes) bubbles with implications for the assessment of geohazards and (human-made and natural) environmental impacts. Specific flow behaviors of slurries also play an important role in biological and medical processes such as blood flow through veins or microbe transport in groundwater. Engineering applications of this project may include food, foam, cement, gel, and ceramics processing. The research proposed here aims at developing a computer code to simulate particle and bubble interactions in slurries at a very small scale to determine how the bulk substance deforms and flows and how it conducts gases. Insights gained at small scales are then up-scaled to the actual spatial and temporal scale of interest. This approach is difficult but important, because small-scale interactions of inclusions (particles, bubbles) have a large effect on the complicated (non-Newtonian) flow behavior of these fluids, where the otherwise often-invoked Navier-Stokes equations can typically not be employed. Therefore, predicting the flow behavior of dense slurries, based on their inclusion properties, has the potential to significantly impact science and engineering dealing with such non-standard, but often encountered and important, fluids. In addition, this project supports a postdoctoral researcher and, through interactions in laboratories, undergraduate and graduate students, who receive interdisciplinary training in mathematical, computer, material, and geophysical science. The developed computer code is expected to be of interest to numerous science and engineering disciplines.