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

表面摩擦阻力是船舶、飞机和卡车运输业的能量损失。该项目探索了使用计算和实验来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壁面摩擦阻力的一种有前途的方法。虽然已经做出了大量的努力来推进壁技术，但该过程尚未完全理解。该项目的主要目的是提供这些新型表面微结构的基本物理的基本理解，并表明它们可以提供壁湍流的系统控制，以最大限度地减少表面摩擦阻力。该项目的成果将通过许多教育和推广活动传播到更广泛的社区，如本科生研究计划，科学出版物，会议演示和夏季科学夏令营，以K-12学生和教师。微型翼型结构，这是一种新提出的表面微观结构，预计将实现独特的湍流控制能力，由于其定义良好的三维几何形状。该项目的主要目标是：（i）证明使用微型翼型结构的湍流控制能力，（ii）识别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）理解微型翼型结构的湍流控制和表面摩擦阻力减小的基本机制，以及（iv）为最大程度地减小表面摩擦阻力，推荐了单个和阵列微翼型结构的最佳构型。直接数值模拟和大涡模拟将用于计算基本流，粒子图像测速技术将用于测量湍流边界层中的速度。通过这个项目获得的基础知识将提供洞察力，以回答有关壁边界湍流动力学的长期问题。微翼型结构所实现的独特湍流控制技术将为航空航天、机械、化学和海洋工程中湍流控制可能导致阻力减小的其他研究领域提供指导。该项目由流体动力学和刺激竞争性研究既定计划（EPSCoR）计划联合资助。该奖项反映了NSF的法定使命，并且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.