Controlling secondary flows by the use of non-wetting surfaces

紊流二次流是自然或人工诱导的垂直于一次流主方向的流动。许多重要的工业过程都有弯曲管道系统和旋转机械，旨在增强和优化化学品和其他流体的混合。这些系统也可能产生紊流二次流。根据二次流的产生方式，它在空间中可能是有序的和静止的，形成停滞区域，即使流动有明显的湍流也会抑制混合。这项研究将更好地理解二次流产生背后的物理原理以及如何控制它们。计算和实验将用于研究使用非润湿（疏水）表面来影响和控制这些流动特征。每年夏天，都会为30多名未被充分代表的少数族裔K-12学生举办一个营地，以鼓励STEM。该项目的目标是研究非润湿表面的使用，通过选择性地对固体边界进行图案化来诱导、影响和控制二次流动。通过直接数值模拟和室内实验相结合的方法，探讨了哪种类型和方式的处理对二次流最有效。将通过测量摩擦损失和流动均匀性来评估不同类型的表面处理的有效性，无论是在流动方向上还是垂直于流动方向上。研究将基于一个已知存在固定二次流的规范系统，即泰勒-库埃特湍流，即两个同心圆柱体之间的流动。模拟将进行，以测试各种各样的表面图案，以确定最有效的安排，通过使用边界条件，类似于理想和现实的处理。实验将非常精确地测量这些治疗方法在现实世界中的疗效。最后，通过对老化表面的研究，估计处理效果的寿命。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。

Turbulent secondary flows are naturally or artificially induced flows perpendicular to the main direction of primary flow. Many important industrial processes have curved-pipe systems and rotating machinery designed to enhance and optimize mixing of chemicals and other fluids. These systems may also produce turbulent secondary flows. Depending on how the secondary flow is generated, it may be ordered and stationary in space creating stagnant regions, which inhibits mixing even if the flow has significant turbulence. This research will provide a better understanding of the physics behind the generation of secondary flows and how to control them. Computations and experiments will be used to investigate using non-wetting (hydrophobic) surfaces to impact and control these flow features. Every summer, a camp will be held for more than 30 underrepresented minority K-12 students to encourage STEM.The goal of this project is to investigate the use of non-wetting surfaces to induce, affect, and control secondary flows through selectively patterning the solid boundaries. By using a combination of direct numerical simulations and laboratory experiments, questions on which types and patterns of treatments are most effective the secondary flows. The effectiveness of different kinds of surface treatments, both in the direction of the flow, and perpendicular to the flow, will be evaluated by measuring frictional losses and flow homogeneity. Investigations will be based on a canonical system where pinned secondary flows are known to exist, namely Taylor-Couette turbulence, i.e. the flow between two concentric cylinders. Simulations will be carried out to test a wide variety of surface patterns to determine the most efficient arrangements by using boundary conditions that resemble both ideal and real treatments. Experiments will measure the real-world efficacy of these treatments with great precision. Finally, by studying aging surfaces, the lifetime of the treatment effectiveness can be estimated.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.