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

高灵敏度的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航行至关重要，在这些地形中，基于视觉的传感器和声纳传感器无法正常工作。人们发现，斑海豹能够仅仅用胡须捕捉周围水的微小扰动来追踪猎物。这归因于密封须抑制尾流中涡激振动的特殊能力。该项目将在韩国科学技术大学（POSTECH）的浦项大学进行密封须的流动实验，由李相俊教授指导。该合作提供了流动设施和设备，以获得独特的数据，这将使人们能够对多个密封须的尾流结构及其对设计高灵敏度水下流量传感器的影响有新的见解。许多研究者利用理想化的晶须模型研究了晶须形态的关键参数对尾流结构的影响。然而，由于密封须的长度、尺寸和扭转沿着长度的自然变化，因此还不能很好地理解真实的密封须如何改变尾流，特别是旋涡脱落。也不清楚一组具有一定构型的晶须如何相互作用以影响尾流特性。由于缺乏对多个密封须在一组中产生的尾流结构的了解，阻碍了设计须启发的高灵敏度水下流量传感器的能力。本研究的目的是了解在雷诺数类似于港口密封须须受到的各种配置的多个密封须的尾流。实验将在水洞中使用粒子成像测速仪（PIV）进行。结果将提供洞察力的个人唤醒如何相互作用，如果相互作用是有益的，以抑制涡脱落。这项研究将填补理解多个真实的密封须产生的尾流结构的差距。最终，这些知识将被用于为在复杂环境中工作的水下机器人开发高灵敏度水下流量传感器。该奖项是东亚和太平洋夏季研究所计划的一部分，由美国国家科学基金会和韩国国家研究基金会共同资助，用于支持美国研究生的夏季研究。

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.