Numerical simulation and vortex analysis of flow turbulence in viscoelastic fluids

粘弹性流体湍流数值模拟与涡流分析

• 批准号: RGPIN-2022-04720
• 负责人: Xi, Li
• 金额: $ 3.35万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=747196
• 关键词: Numerical; simulation; vortex; analysis; flow

Dissolving a minute amount of polymers into a viscous solvent can introduce elasticity to the fluid. Turbulent flow of such viscoelastic fluids can show substantial reduction in its friction drag compared with that of a purely viscous fluid -- up to 80% under certain conditions. With increasing elasticity, drag reduction (DR) behaviors undergo several stages of transitions. Over the past few years, I have established a vibrant research program focusing on the fundamental understanding of the multistage transitions in viscoelastic turbulence using direct numerical simulation (DNS). As we push the boundaries of knowledge in this field, innovative research methods are also being developed along the way. Our specific goals for the next five years are fourfold. The first goal (G1) is an in-depth analysis of the turbulence self-sustaining cycles (SSCs) at the high-elasticity and high-DR limit. This limit has attracted most attention because of the maximum drag reduction (MDR) phenomenon -- existence of a universal upper limit of DR by polymers. Our recent contribution overturned a long-standing fundamental presumption that at MDR turbulent dynamics converges to an invariant "ultimate state". It pointed to an entirely different direction than the past 50 years of MDR research. The proposed work will reveal the nature of this non-convergent dynamics. G2 is to settle a decades-long debate about whether DR is fundamentally attributed to the high extensional viscosity (viscous theory) or elasticity (elastic theory) of polymer solutions. G3 builds on our recently developed VATIP (vortex axis tracking by iterative propagation) method, which allows for fully automated and unbiased turbulent vortex analysis. It will remove a key constraint in the current VATIP algorithm and generalize it for studying all vortex types. G4 is to develop a toolbox around the core VATIP program, including statistical classification of vortices and direct extraction of their life-time dynamics, for application in fundamental turbulence research. These goals build on our recent breakthroughs in both fundamental inquiry and methodology development and are designed to maximize the impact of those advances. G1 and G2 will address the most significant fundamental questions in the field. Physical understanding of those questions will guide the design and selection of drag-reducing polymers for applications in fluid transport and oil drilling and recovery. Methodology development from G3 and G4 will not only support our fundamental inquiry into viscoelastic turbulence, it will also catalyze a paradigm change in turbulence research at large, by shifting the focus from anecdotal observations of flow images to systematic and statistical analysis of vortex dynamics.

将微量聚合物溶解到粘性溶剂中可以为流体带来弹性。与纯粘性流体相比，这种粘弹性流体的湍流可以显着减少摩擦阻力，在某些条件下最多可减少 80%。随着弹性的增加，减阻（DR）行为会经历几个阶段的转变。在过去的几年里，我建立了一个充满活力的研究项目，重点关注使用直接数值模拟（DNS）对粘弹性湍流的多级转变的基本理解。随着我们突破该领域的知识边界，创新的研究方法也在不断发展。我们未来五年的具体目标有四个。第一个目标 (G1) 是对高弹性和高 DR 极限下的湍流自持循环 (SSC) 进行深入分析。由于最大减阻（MDR）现象——聚合物存在普遍的减阻上限，这一限制引起了人们的广泛关注。我们最近的贡献推翻了一个长期存在的基本假设，即在 MDR 下，湍流动力学收敛到不变的“最终状态”。它指出了与过去 50 年 MDR 研究完全不同的方向。拟议的工作将揭示这种非收敛动力学的本质。 G2 旨在解决长达数十年的争论，即 DR 是否从根本上归因于聚合物溶液的高拉伸粘度（粘性理论）或弹性（弹性理论）。 G3 基于我们最近开发的 VATIP（迭代传播涡旋轴跟踪）方法，该方法允许全自动且无偏的湍流涡旋分析。它将消除当前 VATIP 算法中的一个关键约束，并将其推广到研究所有涡流类型。 G4 将围绕核心 VATIP 程序开发一个工具箱，包括涡流的统计分类和直接提取其生命周期动力学，以应用于基本湍流研究。这些目标建立在我们最近在基础探究和方法开发方面取得的突破的基础上，旨在最大限度地发挥这些进步的影响。 G1 和 G2 将解决该领域最重要的基本问题。对这些问题的物理理解将指导用于流体输送和石油钻探和回收的减阻聚合物的设计和选择。 G3 和 G4 方法论的发展不仅将支持我们对粘弹性湍流的基本研究，还将重点从流图像的轶事观察转移到涡动力学的系统和统计分析，从而促进整个湍流研究的范式变化。