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，在这种情况下，从气管-食道假体出来的不稳定流动会产生脉动涡环，冲击到食道弯曲的壁上。由此产生的食道压力场负责成功地产生气管-食道(即替代)语音。因此，了解涡环撞击曲面时产生的机理，特别是产生的压力载荷，可能会提高替换语音的成功率。这项工作也更广泛地适用于生物和工程流动，如心脏血流动力学、流体能量收集、壁面边界湍流等。这些相互作用的物理机制将通过流动可视化以及二维和层析粒子图像测速仪进行研究。速度场的获取将使得能够确定涡度拓扑、压力场估计和识别压力源项，以及在这些相互作用期间产生的壁面载荷。这项提议将研究工作与一个新的外展计划结合起来，帮助高中合唱学生设想对声音艺术表达的兴趣如何导致在科学和工程领域的职业生涯。拟议的工作计划将探索涡环-表面与半球形和圆柱形空腔相互作用的机制。流动显示和粒子图像测速技术将被用来研究靠近空腔的主涡环如何在空腔表面诱导流动，并随后导致流动分离和卷曲成二次涡环，从而潜在地发展方位不稳定性。这种相互作用将在轴对称(半球)和二维腔体几何结构中作为相对于初级涡环半径的腔体半径的函数来研究。凹面上形成的压力载荷也将被量化，以提供对流体-结构相互作用的洞察。这项研究计划的结果将提高气管食道语音的成功率。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在科学和工程领域追求职业生涯，同时还为其中两人提供有偿的暑期研究体验。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。

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.