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

1236351 Plesnik这项研究涉及隆起周围复杂的不稳定(脉动)流动，例如在声带上的息肉或小结。尽管它在工程和生物流动中很普遍，但以前关于从墙上的半球状物体或凸起分离流动的工作都局限于稳定的自由流条件，因此在知识库中造成了一个重大的空白。研究的总体目标是了解脉动流在长径比为2：1的壁面上脉动流动中三维分离所产生的流动结构。这项工作的成果不仅将为生物工程流动应用提供洞察力，还将有助于更广泛的主题，即从边界上光滑轮廓的物体中分离出非定常三维流动。将确定流动结构如何与壁面相互作用，以便阐明它们对突起上游和下游壁面上的剪应力和压力特征的影响。这个次要目标非常重要，因为生物工程流最关心的是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荷，以及与动脉粥样硬化有关的壁面剪切力)。利用时间分辨粒子图像测速仪、激光多普勒测速仪、壁面压力测量、表面摩擦线可视化和油膜干涉法，在风洞中进行了一系列的实验研究，以解决分离的流动形态及其与壁面上感兴趣的流动参数的相互作用。这项拟议研究的变革潜力是促进开发一种前所未有的能力来设计利用非定常三维分离流固有特性的系统。对脉动流动中分离三维流动的详细研究和理解构成了拟议研究的智力优势。声带息肉和小结是在声带上发育的半球状突起，改变了驱动有声语言和产生声音的液体负荷。在动脉中磁靶向给药会导致动脉表面的半球状凝块，扰乱血流动力学。在这两种情况下，突起与脉动流场相互作用。在生物医学和工程应用中，脉动流不仅存在于生物医学中，而且还存在于工程应用中，它是一个基本的流体力学问题，涉及三维流动分离、复杂的旋涡脱落模式以及沿下游壁面的流固相互作用。拟议的研究适用于上述生物工程流动的例子，以及与位于抖动尾流中的物体(例如汽车和海洋空气动力学、风力涡轮机性能等)分离的更广泛的情况，也适用于山丘和护堤周围的环境流动和污染物传输。拟议的研究计划将通过(1)有益于工程和社会环境，(2)增加本科生和代表不足的群体的参与，以及(3)K-12外展计划，实现更广泛的影响。此外，这笔赠款将有助于培养一名博士生和一名博士后学者。信息的传播将通过学术出版物、会议记录和将个人资料系统现有研究网站上的数据存档来实现。此外，针对博士后科学家、研究生和高中生的几项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.