弹惯性湍流的低惯性极限

中文摘要 AI 辅助

粘弹性流体的管道和通道流动在异常低的速度下表现出混沌动力学，这种现象被称为弹惯性湍流（EIT）。一个世纪前首次在实验中被报道，近期的理论研究和模型计算预测了该现象起源的多种情景，从环向应力模态到中心模态，再到Tollmien-Schlichting波。由于缺乏实验确认，实际聚合物溶液流动中的相关情景仍然未知。我们在此通过管道实验确定了EIT的转变阈值，覆盖了弹性数三个数量级的范围。在整个参数范围内，转变在起始时具有中心模态结构。最终，不稳定性在较低的惯性（较高的弹性）极限处发散，这是该中心模态情景的一个稳健特征。最后，我们报告了粘弹性管道流中行波的首次实验观测，所发现的局部结构序列与模型模拟中发现的中心模态行波——"箭头"解——高度吻合。

英文摘要

Pipe and channel flows of viscoelastic fluids display chaotic dynamics at unusually low speeds, a phenomenon referred to as elasto-inertial turbulence, EIT. First reported in experiments a century ago, recent theoretical studies and model computations predict a variety of scenarios for the phenomenon's origin, ranging from hoop stress modes to center modes and to Tollmien-Schlichting waves. Lacking experimental confirmation, the relevant scenario in actual flows of polymer solutions remains unknown. We here determine the transition threshold of EIT in pipe experiments, covering three decades in elasticity number. Across this entire parameter range, the transition features center mode structures at onset. Eventually the instability diverges at a lower inertia (upper elasticity) limit, which is a robust signature of this center mode scenario. Finally, we report the first experimental observation of a traveling wave in viscoelastic pipe flow, and the sequences of localized structures found, are in excellent agreement with a center mode traveling wave, the "arrowhead" solution, discovered in model simulations.

发表机构

• Institute of Science and Technology Austria (ISTA)（奥地利科学技术研究院）
• University of Malaga（马拉加大学）

机构由 AI 辅助整理，请以论文原文为准。