Controlling secondary flows by the use of non-wetting surfaces

湍流二次流是垂直于主流主方向的自然或人工诱导的流动。 许多重要的工业过程都有弯管系统和旋转机械，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湍流二次流。取决于二次流是如何产生的，它可以是有序的并且在空间中是静止的，从而产生停滞区域，这抑制了混合，即使流动具有显著的湍流。这项研究将提供一个更好的理解背后的物理产生的二次流，以及如何控制它们。 计算和实验将被用来研究使用非润湿（疏水）表面来影响和控制这些流动特征。 每年夏天，将为30多名代表性不足的少数民族K-12学生举办一个夏令营，以鼓励STEM。该项目的目标是研究使用非润湿表面，通过选择性地图案化固体边界来诱导，影响和控制二次流。通过直接数值模拟和实验室试验相结合的方法，探讨了何种处理方式对二次流最有效的问题。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。研究将基于已知存在钉扎二次流的规范系统，即Taylor-Couette湍流，即两个同心圆柱之间的流动。将进行模拟，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，类似于理想和真实的治疗。实验将非常精确地测量这些治疗的真实效果。最后，通过研究老化表面，可以估计处理效果的寿命。该奖项反映了NSF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.