Collaborative Research: Unraveling the Spatiotemporal Dynamics of Inertio-Elastic Turbulence using Measurements and Data-Infused Simulations

当聚合物被添加到溶剂中时，即使是在非常稀的溶液中，它们也会以有趣的方式显着改变流体的行为，例如减少流过物体的阻力。在海洋运输应用中，聚合物诱导的减阻可以减少20-25%的摩擦能量损失，从而以减少燃料消耗和二氧化碳排放的形式对社会产生重大影响。然而，在时变三维流体动力学中引起的变化往往是反直觉的，而且很难理解。在某些配置中，聚合物溶液可以引入新的流动不稳定机制，这在典型流体中是不可能的；然而，在其他国家，同样的力量也可能产生看似相反的效果，减轻湍流的能量漩涡运动。湍流结构演变的直接成像是必要的，这需要具有非常高的分辨率和灵敏度的技术。实现这一目标的研究计划与教育和推广计划紧密结合，包括课程开发、补充讲座和互动实验室演示，通过暑期项目为两所大学的高中和大学STEM学生提供工程创新。这项研究包括详细的实验，使用一种独特的成像系统来探测聚合物射流注入周围的牛顿流体是如何变得不稳定的。这些可视化将能够详细表征聚合物射流与周围流体之间的混合以及射流不稳定性的放大率。实验的结果将由首次对相同结构进行测量注入的模拟来补充。通过将测量结果直接整合到模拟中，计算将探测到完全相同的流动，并提供在实验室中无法直接测量的所有额外细节。实验和模拟的耦合结果将为聚合物溶液改变湍流不稳定性的机制提供前所未有的视角。最终，这些见解将解释分子参数（如链延伸性和流动弹性）如何控制聚合物减阻，并有助于指导选择新型生物聚合物来源的添加剂，这些添加剂可以作为传统减阻剂（如从碳氢化合物资源中提取的合成聚合物）的廉价和环保替代品。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。

When polymers are added to a solvent, even in very dilute solutions, they markedly change the behavior of the fluid in intriguing ways, such as reducing the drag force of flow past objects. Polymer-induced drag reduction in marine transport applications can result in 20-25% decrease in frictional energy losses and can thus have a major impact on society in the form of reduced fuel consumption and carbon dioxide emissions. However, the changes induced in the time-varying three-dimensional fluid dynamics are often counter-intuitive and poorly understood. In some configurations, the polymeric solution can introduce new flow instability mechanisms that would not be possible in typical fluids; yet in other regimes, the same forces can also have the seemingly opposite effect of mitigating the energetic eddying motions of turbulence. Direct imaging of the evolution of turbulent flow structures is needed, and it requires a technique with very high resolution and sensitivity. The research plan to achieve this goal is tightly coupled with an education and outreach plan that includes both curriculum development and supplemental lectures and interactive lab demonstrations for Engineering Innovation through summer programs for high-school and college-level STEM students at both universities.The research involves detailed experiments using a unique imaging system to probe how a polymeric jet injected into a surrounding Newtonian fluid becomes unstable. These visualizations will enable a detailed characterization of the mixing between the polymeric jet and the surrounding fluid and the amplification rate of jet instability. The results from the experiments will be complemented by first-of-their-kind measurement-infused simulations of the same configuration. By directly integrating the measurements into the simulations, computations will probe the exact same flow and provide all the additional details that cannot be measured directly in the laboratory. The coupled results from both the experiments and simulations will provide an unprecedented view of the mechanisms through which polymer solutions alter turbulent flow instabilities. Ultimately, such insights will explain how molecular parameters such as chain extensibility and flow elasticity control polymer drag reduction and help guide selection of novel biopolymer sourced additives that can serve as cheap and environmentally friendly substitutes for traditional drag reduction agents such as synthetic polymers derived from hydrocarbon resources.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.