EAPSI: Wake Induced by a Group of Seal Whiskers: Implication to High-sensitivity Underwater Flow Sensors

高灵敏度水下流量传感器对于自主水下航行器（auv）在黑暗、狭窄和不稳定的地形中导航至关重要，在这些地形中，视觉和声纳传感器无法很好地发挥作用。人们发现斑海豹仅凭胡须就能捕捉到周围水的微小波动，从而追踪猎物。这要归功于密封晶须在尾流中抑制涡激振动的特殊能力。该项目将在韩国浦项理工大学（POSTECH）进行海豹须的流动实验，由Sang Joon Lee教授指导。此次合作提供了流动设施和设备，以获得独特的数据，从而对多个密封须的尾迹结构有了新的认识，并有助于设计高灵敏度的水下流动传感器。许多研究者利用理想的类须模型研究了须形态关键参数对尾流结构的影响。然而，由于海豹须的长度、大小和扭曲度的自然变化，人们对真正的海豹须如何改变尾流，特别是旋涡脱落，还不是很清楚。同样不清楚的是，一组具有特定结构的晶须如何相互作用以影响尾流特性。由于缺乏对多个海豹须在一组中产生的尾流结构的了解，阻碍了设计基于须的高灵敏度水下流量传感器的能力。本研究的目的是了解不同结构的多个海豹须在相似的雷诺数下的尾迹。实验将在水洞中使用粒子成像测速仪（PIV）进行。研究结果将提供个体尾流如何相互作用以及这种相互作用是否有利于抑制涡脱落的见解。本研究将填补对多个真实海豹须产生的尾迹结构的理解空白。最终，这些知识将用于开发高灵敏度的水下流量传感器，用于在复杂环境中运行的auv。该奖项是由美国国家科学基金会（NSF）和韩国国立科学研究财团（National research Foundation）共同资助的东亚太平洋暑期研究所（East Asia and Pacific Summer Institutes）项目，为美国研究生的暑期研究提供支持。

High-sensitivity underwater flow sensors are critical for autonomous underwater vehicles (AUVs) to navigate through dark, cramped, and unstable terrain where vision-based and sonar sensors do not function well. Harbor seals are found to be able to track their prey by capturing even minute disturbance of the ambient water solely by using their whiskers. This is attributed to the exceptional capability of seal whiskers to suppress vortex-induced vibration in the wake flow. This project will conduct flow experiments of seal whiskers at Pohang University of Science and Technology University (POSTECH) in South Korea, under the mentorship of Professor Sang Joon Lee. The collaboration provides flow facilities and equipment to obtain unique data that will enable new insights into the wake structure of multiple seal whiskers and its implication to design high-sensitivity underwater flow sensors. Many researchers have studied the effects of key parameters of the whisker morphology on wake structure with idealized whisker-like models. However, due to the natural variation in length, size and twist along the length of seal whiskers, it is not well understood how a real seal whisker changes wake flow, in particular the vortex shedding. It is also unclear how a group of whiskers with a certain configuration interact with each other to affect the wake properties. Lack of knowledge of the wake structure generated by multiple seal whiskers in a group hinders the capability to design whisker-inspired high-sensitivity underwater flow sensors. The goal of this research is to understand the wake of multiple seal whiskers of various configurations at the Reynolds number similar to which harbor seal whiskers are subject to. Experiments will be conducted in a water tunnel using Particle Imaging Velocimetry (PIV). The results will provide insights of how individual wakes interact with each other and if the interaction is beneficial to suppress the vortex shedding. This research will fill the gap of understanding the wake structure that multiple real seal whiskers create. Ultimately knowledge will be used to develop high-sensitivity underwater flow sensors for AUVs operating in a complex environment.This award, under the East Asia and Pacific Summer Institutes program, supports summer research by a U.S. graduate student and is jointly funded by NSF and the National Research Foundation of Korea.