Collaborative Research: 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移动时，流动组织成相干涡流，这些涡流从主体的交替侧脱落，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。本计画研究借由沿著圆柱体沿着增加起伏来减缓非定常涡型态及相关振动力的潜在方法。特定几何形状受到密封须的启发，密封须表明，在某些流动条件下，沿表面沿着交替的波动图案可显著降低涡激振动。特别令人感兴趣的是，如何修改波状结构后面的尾流，以及它又如何影响紧密堆积的结构系统。这有各种潜在的应用，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生研究项目和K-12推广计划整合到现有的传播机制，在威斯康星大学麦迪逊分校和波特兰州立大学。这项研究探讨了基本的流体流动机制的波动缸和波动缸阵列的启发，独特的地形密封胡须。波动的几何特征之间的因果关系，产生的流动特征，和力和频率响应的圆柱体将被定量识别的关键点和其他关键标记的动量和能量转移方面的尾流。在单圆柱数据的基础上，将为小型和大型阵列配置开发和测试尾流-尾流和尾流-结构相互作用的框架。模拟和风洞实验都将用于一个互补和协作的研究计划，该计划涵盖了大范围的流动条件和配置。这将通过粒子图像速度测量来完成详细的尾流测量，以及直接数值模拟和大涡模拟来实现时间分辨力和近尾流区域机制的量化。该奖项反映了NSF的法定使命，并被认为值得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来支持。

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.