Collaborative Proposal: Linking the topographic features of bio-inspired undulated cylinders to their force reduction properties using critical points

当流体围绕圆柱形或类似形状的结构运动时，流动会组织成连贯的涡流，这些涡流从身体的交替一侧脱落，产生振动力。这种涡激振动是一种不良后果，在工程设计中具有深远的影响，从长圆柱形系泊或传输线到桥梁的结构支撑，以及许多其他易受流体流动影响的应用。该项目研究了通过沿圆柱体添加起伏来减轻非定常涡流模式和相关振动力的潜在方法。特殊的几何形状的灵感来自于密封件的晶须，这表明在特定的流动条件下，沿表面的交替起伏图案显著地减少了涡激振动。尤其令人感兴趣的是，波状结构背后的尾迹如何被修改，以及它将如何反过来影响紧密堆积的结构系统。这具有各种潜在的应用，从水动力传感器阵列，风力涡轮机农场的设计，或研究不均匀的森林树冠和山区的天气模式。教育部分将包括多个本科生研究项目和K-12推广计划，整合到威斯康星大学麦迪逊分校和波特兰州立大学现有的传播机制中。这项研究探索了波状圆柱体和波状圆柱体阵列上流动的基本流体机制，灵感来自于海豹胡须的独特地形。波动的几何特征、由此产生的流动特征以及圆柱体的力和频率响应之间的因果联系将通过尾迹中的临界点和其他关键标志来定量地识别，这些标志涉及动量和能量转移。在单柱体数据的基础上，将开发一个尾迹-尾迹和尾迹-结构相互作用的框架，并针对小型和大型阵列配置进行测试。模拟和风洞实验将被用于一个互补和协作的研究计划，该计划跨越大范围的流动条件和构型。这将通过粒子图像测速仪进行详细的尾迹测量，以及对时间分辨的力和近尾迹区域机制的量化进行直接数值模拟和大涡模拟。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

As a fluid moves around a cylindrical or similarly shaped structure, the flow organizes into coherent vortices, which shed from alternate sides of the body producing a vibrational force. This vortex-induced-vibration is an undesirable consequence with far-reaching effects in engineering design, from long cylindrical mooring or transmission lines to structural supports of bridges, as well as many other applications susceptible to fluid flow. This project investigates potential methods to mitigate the unsteady vortex pattern and associated vibrational force by adding undulations along the cylinder. The specific geometry is inspired by the whiskers of seals which have shown that an alternating undulation pattern along the surface significantly reduces the vortex-induced-vibration under certain flow conditions. Of particular interest is how the wake behind the undulated structures can be modified and how it, in turn, would impact a system of closely packed structures. This has a variety of potential applications from hydrodynamic sensor arrays, the design of wind turbine farms, or the study of weather patterns over non-uniform forest canopies and mountainous terrain. The educational components will include multiple undergraduate research projects and K-12 outreach programming integrated into existing dissemination mechanisms at University of Wisconsin-Madison and Portland State University.This research explores the fundamental fluid mechanisms of flow over undulated cylinders and arrays of undulated cylinders inspired by the unique topography of seal whiskers. Causal links between the geometric features of the undulations, the resulting flow features, and the force and frequency response of the cylinder will be quantitatively identified by critical points and other key markers within the wake in terms of momentum and energy transfer. Building upon the single-cylinder data, a framework for wake-wake and wake-structure interactions will be developed and tested for small and large array configurations. Both simulations and wind tunnel experiments will be utilized in a complementary and collaborative research plan that spans a large range of flow conditions and configurations. This will be accomplished through particle-image-velocimetry for detailed wake measurements as well as direct numerical simulation and large-eddy simulations for time-resolved forces and quantification of mechanisms in the near-wake region.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.