EAGER: A Novel 3-D Printed PVDF-TrFE Copolymer Wall Shear Stress Measuring Device for Measurement of Wall Shear Stress in Unsteady Flow Applications

壁面剪切应力的测量和剪切应力在气动和生理流动应用中的影响是至关重要的。尽管在气动和生理流体流动研究方面有广泛的文献，但对非定常流的许多基本性质了解甚少。各种非定常流动模型实验验证的主要限制是流动测量仪器的不足，特别是直接无创测量壁面剪切应力的方法。复杂非定常流场壁面剪切应力的灵敏度和精度是现有最先进的测量技术无法达到的。本研究旨在研究多层3d打印压电聚偏氟乙烯-三氟乙烯（PVDF-TrFE）共聚物传感器作为壁剪应力测量装置的候选器件。所提出的技术的优点在于它不包含活动部件，可以潜在地直接测量壁面剪切应力，可以直接安装到流动表面而不需要修改，并且与现有方法相比，可以很容易地制造。初步结果表明，PVDF-TrFE对偏转具有较高的灵敏度和精度。这项研究的重点是实现这种新型传感器技术，在非定常流场应用中直接测量壁面剪应力。这项研究工作将解决与灵敏度相关的问题，传感器的安装，用粒子成像测速法测量传感器测量结果的验证，用泊泽维尔流、沃默斯利流和斯托克斯流的精确解析解，以及传感器厚度引入的误差问题。如果所提出的努力取得成功，所提出的方法将为各种尺寸的嵌入式传感器的制造和实施提供便利，这些传感器消除了运动部件，增加了鲁棒性，降低了流量仪表工具的成本，并提供了非侵入式壁面剪切应力测量。PVDF-TrFE传感器从未被测试或用于墙壁剪切传感，因此提供剪切转导的机电耦合机制尚未完全了解。这项开创性的研究工作将确定PVDF-TrFE在墙剪力下的基本传感特性，改进传感器的制造和包装，并将开发一种高频动态校准方法。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。

Wall shear stress measurements and the influence of shear stresses in aerodynamic and physiological flow applications are vital. Although there is widespread literature in aerodynamic and physiological fluid flow research, many of the basic properties of unsteady flows are poorly understood. A major limitation in the experimental validation of various unsteady flow models is insufficient flow measurement instrumentation, specifically a method of direct non-invasive measurement of wall shear stress. The sensitivity and accuracy needed to evaluate the wall shear stresses in complex unsteady flows is not attainable with the existing state-of-the-art measurement technologies. This research effort aims to investigate a multi-layered 3-D printed piezoelectric polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) copolymer sensor as a wall shear stress measuring device candidate. The proposed technology has an advantage in that it contains no moving parts, can potentially perform a direct measurement of wall shear stress, can be mounted directly to the flow surface with no modification, and can be manufactured easily as compared to existing methods. Preliminary results demonstrate that PVDF-TrFE exhibits exceptional sensitivity to deflection with high accuracy and sensitivity.This research effort will focus on implementing this novel sensor technology to perform direct wall shear stress measurements in unsteady flow applications. This research effort will address issues related to sensitivity, installation of the sensor, validation of sensor measurements with particle imaging velocimetry wall shear stress measurements and with exact analytical solutions for Poiseuille, Womersley and Stokes flows, and issues of error introduced by the sensor thickness. If the proposed effort is successful, the proposed methodology will provide ease of fabrication and implementation for a range of sizes of flush mountable sensors that eliminate moving parts increasing robustness, provides a reduction of cost in flow instrumentation tools, and provides a non-intrusive wall shear stress measurement. PVDF-TrFE sensors have never been tested or used for wall shear sensing, thus the electromechanical coupling mechanism that provides shear transduction is not fully understood. This pioneering research effort will determine the fundamental sensing properties of PVDF-TrFE under wall shear, improve sensor fabrication and packaging, and will develop a methodology for high frequency dynamic calibration.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.