EAGER: Novel Instrumentation for Extracting and Modeling of Flow Structure in Turbulent Boundary Layers

开发新的、更高效的空气动力飞行器是一个不断进行的过程。可以针对许多领域进行改进，包括减少阻力、增强机动性和降低噪音水平。虽然在空气动力学方面有很长的研究记录，但人们对流体流动的许多基本性质并不完全了解。例如，沿运动物体表面的力如何与周围空气中的速度有关。部分原因是缺乏适当的工具来测量这些流动相互作用，这限制了可以进行的实验。该项目旨在开发新的工具，用于在多个方向上测量流动产生的摩擦，以便它们可以与现有的估计流速的工具相结合，最终目标是生成湍流运动的综合实验模型。这些努力揭示的信息将加强对基本湍流的理解，这可以推广到其他更复杂的相互作用。此外，传感器技术的广泛进步可以被其他研究小组用于他们未来的工作，使下一代空气动力学性能得以提高。充分了解壁力和湍流流场中的自由流流体速度之间的相互作用仍然难以捉摸，它的研究需要新的技术。具体地说，脉动壁面剪应力与边界层内相干湍流结构大尺度运动之间的时间关系等。对各种模型进行实验验证的一个关键限制是测量仪器不足，特别是在多维流动中。基于微电子机械系统(MEMS)的传感器就是为了解决这一问题而开发的，包括将壁面剪应力测量能力从单轴扩展到时间分辨矢量。具体地说，提出了一种具有液压光滑封装的双轴差动电容式浮动元件摩阻传感器。该新型传感器将提供对高剪切事件触发的速度场进行采样的机会，从而能够更深入地了解湍流边界层中的许多悬而未决的问题，包括涡流的形成、传播和马蹄形涡旋模型的准确性。它还将提供在微尺度上进行壁面剪应力的时间分辨矢量测量的能力，这是目前尚不存在的。新型MEMS传感器的开发将继续扩大为流体应用量身定做的不断增长的传感器套件，从而为空气动力学家提供可在其他地方使用的仪器级工具。

Development of new, more efficient aerodynamic vehicles is a constantly ongoing process. There are many areas of improvement that can be targeted, including reduced drag, enhanced maneuverability, and reduced noise levels. Although there is a long track record of research in aerodynamics, many of the basic properties of fluid flows are not completely understood. For instance, how forces along the surface of a body in motion relate to velocity in the surrounding air. Part of the reason is a lack of proper tools for measuring these flow interactions, which limits the experiments that can be performed. This project looks to develop new tools for the measurement of the flow-generated friction in multiple directions such that they can be combined with existing tools that estimate flow velocity with an ultimate goal of generating comprehensive experimental models of the turbulent motions. Information revealed from these efforts will enhance understanding of fundamental turbulent flows, which can be generalized to other more complex interactions. Furthermore, broad advances in sensor technology can be used by other research groups in their future endeavors, enabling increases in the next generation of aerodynamic performance.A full understanding of the interplay between wall forces and freestream fluid velocity within turbulent flow fields remains elusive and its study requires new technologies. Specifically, the temporal relationship between fluctuating wall shear stress and large scale motion of coherent turbulent structures in a boundary layer, among others. A key limitation to experimental validation of various models is insufficient measurement instrumentation, especially in multi-dimensional flows. Microelectromechanical system (MEMS) based transducers are developed to address this gap, including extending wall shear stress measurement capabilities from single-axis to time-resolved vectors. Specifically, a dual-axis, differential capacitive floating element skin friction sensor possessing a hydraulically smooth package is proposed. The novel sensor will provide the opportunity to sample the velocity field triggered by high-shear events allowing for greater insight into numerous open questions on turbulent boundary layers, including eddy formation, propagation, and the accuracy of the horseshoe vortex model. It will also provide the ability to make time-resolved vector measurements of wall shear stress at the microscale, which does not currently exist. Development of the novel MEMS sensors will continue to expand on the growing suite of transducers tailored for fluid applications, leading to instrument grade tools for aerodynamicists to utilize elsewhere.