Brave new whorl: Vortex ring impingement on concave surfaces

涡环与固体和可变形表面的相互作用在自然界和工程流动中大量存在。这种情况与喉切除术后的替代语音问题特别相关，其中离开气管食管假体的不稳定流产生冲击食管弯曲壁的脉动涡环。所得到的食管压力场负责成功地产生气管食管（即，替换）演讲。因此，了解涡流环冲击曲面时产生的力学，特别是产生的压力载荷，可以提高语音置换的成功率。这项工作也更广泛地适用于生物和工程流，如心脏血液动力学，流体能量收集，壁边界湍流等这些相互作用的物理将通过流动可视化和二维和断层粒子图像测速研究。速度场的采集将能够确定涡度拓扑、压力场估计和压力源项的识别，以及在这些相互作用期间产生的所得壁载荷。这项提案将研究工作与一项新的推广计划相结合，以帮助高中合唱学生设想如何对声音艺术表达的兴趣能够导致科学和工程职业生涯。拟议的工作计划将探讨涡环-表面与半球形和圆柱形空腔相互作用的机制。流动可视化和粒子图像测速将被用来探索如何接近一个空腔的主要涡环诱导流动的空腔的表面上，随后导致流动分离和卷起到一个次要的涡环，并可能发展方位角不稳定性。将在轴对称（半球形）和二维空腔几何形状中研究这种相互作用，作为空腔半径相对于主涡环半径的函数。在凹面上产生的压力载荷也将被量化，以提供对流体-结构相互作用的了解。本研究计划的结果将提高气管食管发音的成功率。该项目还将促进一名研究生和多名本科生的培训和教育。最后，该推广计划将激励高中生从事科学和工程领域的职业，同时还为其中两名学生提供带薪暑期研究经验。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Vortex ring interactions with solid and deformable surfaces abound in nature and engineering flows. This situation is particularly relevant to the problem of replacement speech following a laryngectomy, where unsteady flow exiting a tracheoesophageal prosthesis produces pulsatile vortex rings that impinge on the curved wall of the esophagus. The resultant esophageal pressure field is responsible for successfully producing tracheoesophageal (i.e., replacement) speech. As such, understanding the mechanics that arise as vortex rings impact curved surfaces, in particular the pressure loading that is produced, could lead to improved success rates of replacement speech. This work is also more broadly applicable to both biological and engineering flows, such as cardiac hemodynamics, fluidic energy harvesting, wall-bounded turbulence, etc. The physics of these interactions will be investigated via flow visualization and both two-dimensional and tomographic particle image velocimetry. Acquisition of the velocity fields will enable determination of vorticity topologies, pressure field estimation, and identification of pressure source terms, as well as the resultant wall loading that arises during these interactions. This proposal blends the research efforts with a novel outreach plan to help high-school choral students envision how an interest in artistic expression in voice can lead to a career in science and engineering. The proposed work plan will explore the mechanics of vortex ring-surface interactions with both hemispherical and cylindrical cavities. Flow visualization and particle image velocimetry will be utilized to explore how a primary vortex ring approaching a cavity induces flow on the surface of the cavity, and subsequently causes the flow to separate and roll-up into a secondary vortex ring, and potentially develop azimuthal instabilities. This interaction will be investigated in both axisymmetric (hemispherical) and two-dimensional cavity geometries as a function of cavity radius relative to the primary vortex ring radius. The pressure loading that develops on the concave surface will also be quantified to provide insight into the fluid-structure interaction. The outcomes from this research plan will improve success rates of tracheoesophageal speech. The project will also facilitate the training and education of one graduate and multiple undergraduate students. Finally, the outreach program will inspire high-school students to pursue careers in science and engineering fields, while also providing paid summer research experiences for two of them.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.