As extreme events increase in frequency, flow-disrupting large-scale structures become ever more susceptible to collapse due to local scour effects. The objective of this study was to validate the functionality of passive, flow-excited scour sensors that can continue to operate during an extreme event. The scour sensors, or piezo-rods, feature continuous piezoelectric polymer strips embedded within and along the length of slender cylindrical rods, which could then be driven into the soil where scour is expected. When scour erodes away foundation material to reveal a portion of the piezo-rod, ambient fluid flow excitations would cause the piezoelectric element to output a voltage response corresponding to the dynamic bending strains of the sensor. The voltage response is dependent on both the structural dynamic properties of the sensor and the excitation fluid’s velocity. By monitoring both shedding frequency and flow velocity, the exposed length of the piezo-rod (or scour depth) can be calculated. Two series of experimental tests were conducted in this work: (1) the piezo-rod was driven into sediment around a mock pier to collect scour data, and (2) the piezo-rod was used to monitor its own structural response by collecting vortex-shedding frequency data in response to varied flow velocities to establish a velocity–frequency relationship. The results showed that the piezo-rod successfully captured structural vortex-shedding frequency comparable to state-of-practice testing. A one-dimensional numerical model was developed using the velocity–frequency relationship to increase the accuracy of voltage-based length prediction of the piezo-rod. Two-dimensional flow modeling was also performed for predicting localized velocities within a complex flow field. These velocities, in conjunction with the velocity–frequency relationship, were used to greatly improve length-predictive capabilities.

随着极端事件频率的增加，由于局部冲刷效应，扰乱流动的大型结构变得越来越容易倒塌。本研究的目的是验证在极端事件期间可以继续运行的被动、流动激励冲刷传感器的功能。冲刷传感器或压电棒的特点是连续的压电聚合物条嵌入细长圆柱形棒的内部和长度，然后可以将其推入预计会冲刷的土壤中。当冲刷侵蚀掉基础材料以露出压电杆的一部分时，周围的流体流动激励将导致压电元件输出对应于传感器动态弯曲应变的电压响应。电压响应取决于传感器的结构动态特性和激励流体的速度。通过监测脱落频率和流速，可以计算压电杆的暴露长度（或冲刷深度）。在这项工作中进行了两个系列的实验测试：（1）将压电杆打入模拟码头周围的沉积物中以收集冲刷数据，以及（2）使用压电杆通过收集涡流来监测其自身的结构响应- 响应不同流速的频率数据以建立速度-频率关系。结果表明，压电棒成功捕获了与实践测试相当的结构涡旋脱落频率。使用速度-频率关系开发了一维数值模型，以提高基于电压的压电杆长度预测的准确性。还进行了二维流建模以预测复杂流场内的局部速度。这些速度与速度-频率关系相结合，被用来大大提高长度预测能力。