Controlling secondary flows by the use of non-wetting surfaces

湍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。许多重要的工业流程都有弯管系统和旋转机械，旨在加强和优化化学品和其他流体的混合。这些系统还可能产生湍急的二次流。根据二次流的产生方式，二次流在空间中可能是有序的和静止的，从而产生停滞区，这阻止了混合，即使流动有明显的湍流。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。计算和实验将被用来研究使用非湿(疏水)表面来影响和控制这些流动特征。每年夏天，将为30多名未被充分代表的K-12少数族裔学生举办一次夏令营，以鼓励STEM。该项目的目标是调查非湿润表面的使用，通过选择性地绘制固体边界的图案来诱导、影响和控制二次流。通过使用直接数值模拟和实验室实验相结合的方法，可以确定哪些类型和模式的处理最有效，以减少二次流。将通过测量摩擦损失和流动均匀度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正则系统，即Taylor-Couette湍流，即两个同心圆柱体之间的流动。将进行模拟，以测试各种表面图案，以通过使用与理想和真实处理相似的边界条件来确定最有效的布置。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，可以估计治疗效果的寿命。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.