Wall Turbulence Control and Skin-Friction Drag Reduction with Novel Surface Microstructures

表面摩擦阻力是造成船舶、飞机和卡车运输行业能量损失的主要原因。本项目通过计算和实验探索减少表面摩擦阻力的创新方法。利用表面微结构被动地抑制壁面湍流是减小表面摩擦阻力的一种很有前途的方法。虽然人们已经为推进墙技术做出了大量的努力，但这个过程还没有完全被理解。该项目的主要目的是提供对这些新型表面微观结构的潜在物理的基本理解，并表明它们可以提供对壁湍流的系统控制，以最小化表面摩擦阻力。项目成果将通过许多教育和推广活动传播到更广泛的社区，如本科研究计划、科学出版物、会议报告和面向K-12学生和教师的暑期科学营。一个微型翼型结构，这是一个新提出的表面微观结构，有望实现独特的湍流控制能力，由于其明确的三维几何形状。该项目的主要目标是：(i)展示了使用微型翼型结构的湍流控制能力，（ii）确定了由微型翼型结构产生的控制输入与表面摩擦阻力响应之间的联系，（iii）了解了微型翼型结构的湍流控制和表面摩擦阻力减少的基本机制。(4)推荐单翼型和微翼型阵列结构的最佳配置，以最大限度地减少表面摩擦阻力。直接数值模拟和大涡模拟将用于计算基本流动，粒子图像测速将用于测量湍流边界层中的速度。通过该项目获得的基础知识将为回答关于壁面湍流动力学的长期问题提供见解。微翼型结构实现的独特湍流控制技术将为航空航天、机械、化学和海洋工程等领域的湍流控制可能导致阻力减少的研究领域提供指导。该项目由流体动力学和建立计划，以刺激竞争研究（EPSCoR）计划共同资助。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。

Skin-friction drag is responsible for energy loss for ships, aircraft, and the trucking industry. This project explores innovative methods of reducing skin-friction drag using computations and experiments. One of the promising methods for reducing skin-friction drag is to dampen wall turbulence passively using surface microstructures. While a substantial amount of effort has been made to advance wall techniques, the process is not yet completely understood. The primary aim of this project is to provide a fundamental understanding of the underlying physics of these novel surface microstructures and show that they can provide systematic control of wall turbulence to minimize skin-friction drag. The project outcomes will be disseminated to broader communities through many educational and outreach activities, such as undergraduate research programs, scientific publications, conference presentations, and summer science camps to K-12 students and teachers.A micro airfoil structure, which is a newly proposed surface microstructure, is expected to achieve unique turbulence control capabilities due to its well-defined 3D geometry. The main objectives of the project are: (i) to demonstrate the turbulence control capability using the micro airfoil structure, (ii) to identify the connections between the control inputs created by the micro airfoil structure and the responses of skin-friction drag, (iii) to understand the fundamental mechanisms of the turbulence control and skin-friction drag reduction by the micro airfoil structure, and (iv) to recommend the optimum configurations of the single and arrays of micro airfoil structure for the maximum reduction of skin-friction drag. Direct numerical simulation and large eddy simulation will be used to compute fundamental flows, and particle image velocimetry will be used to measure velocities in the turbulent boundary layer. The fundamental knowledge obtained through this project will provide insight to answer the long-lasting questions about the dynamics of wall-bounded turbulent flows. The unique turbulence control techniques achieved by the micro airfoil structure will provide guidance to other research areas in aerospace, mechanical, chemical, and ocean engineering where turbulence control may lead to drag reduction. This project is jointly funded by Fluid Dynamics and the Established Program to Stimulate Competitive Research (EPSCoR) programs.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.