Three-dimensional Separated Flows around a Bump Imbedded in a Boundary Layer with Pulsatile Freestream: Biofluid Dynamics of Phonation

1236351 Plesniak本研究涉及到围绕一个突起的复杂的非稳定（脉动）流动，例如声带息肉或结节中遇到的流动。 尽管它在工程和生物流动中的流行，以前的工作从一个半球状物体，或凸块，在墙上的流动分离都被限制在稳定的自由流动条件下，从而在知识库中创建一个显着的空白。 研究的总体目标是了解在壁面上纵横比为2：1的扁长半球体上脉动流的三维流动分离所产生的流动结构。这项工作的成果将提供洞察力，不仅进入生物工程流的应用，但也有助于更广泛的主题，不稳定的三维流动分离，从光滑轮廓的物体上的边界。 将确定流动结构如何与壁相互作用，以阐明它们对突起上游和下游壁上的剪切应力和压力信号的影响。这个次要目标非常重要，因为生物工程流最关心引起生物反应的流体-结构相互作用（例如，驱动有声语音动态的压力负载，以及与动脉粥样硬化有关的壁剪切应力）。一套实验研究将在风洞中进行，利用时间分辨粒子图像测速仪，激光多普勒测速仪，壁压测量，表面摩擦线可视化，和油膜干涉，以解决分离流的形态，和他们的相互作用与流动参数的兴趣在墙上。所提出的研究的变革潜力是促进发展一个前所未有的能力，设计系统，利用非定常三维分离流的固有特征，详细的研究和了解的脉动流中的分离的三维流动构成了所提出的研究的智力价值。声带息肉和小结是在声带上形成的半球形突起，改变了驱动浊音语音并产生声音的流体负荷。动脉中的磁靶向药物递送导致动脉表面上的半球形聚集物，破坏血液动力学。在这两种情况下，突起与脉动流场相互作用。脉动流不仅在生物医学领域，而且在工程应用中也有广泛的应用，它是一个基本的流体力学问题，涉及到三维流动分离、复杂的旋涡脱落模式以及沿着下游壁面的流体-结构相互作用。所提出的研究适用于上述生物工程流的例子，以及来自位于抖振尾流中的物体的流分离的更广泛的情况（例如，汽车和海洋空气动力学、风力涡轮机性能等），以及山丘和护堤周围的环境流动和污染物迁移。 拟议的研究计划将通过（1）有利于工程和社会环境，（2）增加本科生和代表性不足的群体的参与，以及（3）K-12外展计划，实现更广泛的影响。 此外，赠款将促进培养一名博士。学生和博士后学者。 信息的传播将通过学术出版物、会议记录和PI现有研究网站上的数据档案来实现。 此外，一些针对博士后科学家、研究生和高中生的辅导活动正在进行中。

1236351PlesniakThis investigation concerns the complicated unsteady (pulsatile) flow around a protuberance, such as encountered in polyps or nodules on the vocal folds. Despite its prevalence in engineering and biological flows, the previous work on flow separation from a hemispheroid-like object, or bump, on a wall has all been limited to steady freestream flow conditions, thus creating a significant void in the knowledge base. The overall objective of the investigation is to understand flow structures produced by three-dimensional flow separation in pulsatile flow over a 2:1 aspect ratio prolate hemispheroid on a wall. The outcomes of this work will provide insight not only into bioengineering flow applications, but also contribute to the broader topic of unsteady three-dimensional flow separation from smoothly-contoured objects on a boundary. It will be determined how flow structures interact with the wall in order to elucidate their impact on the shear stress and pressure signature on the wall both upstream and downstream of the protuberance. This secondary objective is of great importance because bioengineering flows are most concerned with fluid-structure interactions that elicit a biological response (e.g. pressure loadings that drive the dynamics of voiced speech, and wall shear stresses that have been linked to atherosclerosis). A suite of experimental investigations will be performed in a wind tunnel, utilizing time-resolved particle image velocimetry, laser Doppler anemometry, wall pressure measurements, skin friction line visualization, and oil-film interferometry, in order to resolve the separated flow morphologies, and their interaction with flow parameters of interest on the wall. The transformative potential of the proposed study is to facilitate the development of an unprecedented ability to design systems that take advantage of inherent features of unsteady 3-D separated flows.Detailed study and understanding of separated 3-D flows in pulsatile flows constitutes the intellectual merit of the proposed study. Vocal fold polyps and nodules are hemispheroidal protuberances that develop on the vocal folds, altering the fluid loading that drives voiced speech and produces sound. Magnetically-targeted drug delivery in the arteries results in hemispheroidal conglomerations on the arterial surface, disrupting the hemodynamics. In both scenarios, the protuberance interacts with a pulsatile flow field. Found not only in biomedical, but also engineering applications, pulsatile flow over a bump on a wall presents a fundamental fluid mechanics problem involving three-dimensional flow separation, complex vortex shedding patterns, and fluid-structure interactions along the downstream wall. The proposed research is applicable to the aforementioned examples of bioengineering flows, as well as to the broader case of flow separation from objects that are located in a buffeting wake (e.g. automobile and marine aerodynamics, wind turbine performance, etc.), and also to environmental flows and contaminant transport around hills and berms. The proposed research plan will achieve broader impacts by (1) benefiting engineering and societal environments, (2) increasing participation of undergraduates and underrepresented groups, and (3) K-12 outreach programs. Furthermore, the grant will facilitate the training of a Ph.D. student and a post-doctoral scholar. Dissemination of information will be achieved through scholarly publications, conference proceedings, and the archival of data on the PIs existing research website. Additionally, several mentoring activities for post-doctoral scientists, graduate, and high school students are underway.