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

当流体在圆柱形或类似形状的结构周围运动时，流动形成连贯的漩涡，这些漩涡从物体的两侧脱落，产生一种振动力。在工程设计中，从长圆柱形系泊或输电线路到桥梁的结构支撑，以及许多其他易受流体流动影响的应用，这种涡激振动是一种不良后果，具有深远的影响。本项目研究了通过增加沿柱体的波动来减轻非定常涡型和相关的振动力的潜在方法。特殊的几何形状的灵感来自于密封须，这表明在一定的流动条件下，沿表面的交替波动模式显着减少了涡激振动。特别令人感兴趣的是如何改变波动结构后面的尾流，以及它反过来如何影响紧密排列结构的系统。这有各种各样的潜在应用，从流体动力传感器阵列，风力涡轮机农场的设计，或在不均匀的森林树冠和山区地形的天气模式的研究。教育部分将包括多个本科研究项目和K-12外展计划，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。本研究探索了受海豹须独特地形启发而流过波动圆柱体和波动圆柱体阵列的基本流体机制。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关系将通过尾迹中的临界点和其他关键标记在动量和能量传递方面定量地确定。在单缸数据的基础上，将开发一个尾流-尾流和尾流-结构相互作用的框架，并对小型和大型阵列配置进行测试。模拟和风洞实验将在一个互补和合作的研究计划中得到利用，该计划将跨越大范围的流动条件和配置。这将通过粒子图像测速法来实现详细的尾迹测量，以及直接数值模拟和大涡模拟来实现时间分辨力和近尾迹区域机制的量化。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。

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.