Characterizing Transition to Turbulence in Pulsatile Pipe Flow

表征脉动管流中的湍流转变

• 批准号: 2335760
• 负责人: Melissa Brindise
• 金额: $ 32.17万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-02-01 至 2027-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2335760&HistoricalAwards=false
• 关键词: Characterizing; Transition; Turbulence; Pulsatile; Pipe

Transitional and turbulent pulsatile flows have been observed in a variety of applications including biomedical flows such as flow through the heart, aorta, and brain. Transitional flow causes significant fluctuations in flow parameters such as pressure and wall shear stress, which can precipitate major practical consequences. For example, these fluctuations can accelerate the progression of vascular diseases including heart disease, stenoses, etc.; additionally, they can weaken materials to failure, i.e., expediting the rupture of aneurysms. Thus, to accurately evaluate these biomedical conditions, it is important to consider and quantify the role of transitional flow effects. Unfortunately, transition to turbulence in pulsatile flows remains a poorly understood flow regime. As a result, current studies most often ignore the effects of transitional flow. Therefore, the principal aim of this project is to provide a fundamental understanding of the pulsatile transitional flow regime as well as build universal tools capable of estimating its functional effects. This project will also focus on expanding training and educational resources related to experimental fluid dynamic methodologies. Additionally, the vast amount of experimental data collected through this project will be made publicly available and used to establish a globally accessible repository of difficult-to-obtain experimental transitional and turbulent flow data.The goal of this project is to establish fundamental knowledge regarding the mechanisms that drive transition in pulsatile pipe flow as well as develop first-of-their-kind tools capable of estimating intermittency and transition progression. To date, studies exploring this flow regime have been limited to one-off contributions and produced contradictory findings. The lack of consensus and understanding of this flow regime has increasingly led to biomedical studies controversially asserting flows with mean Reynolds numbers as low as 250 as being transitional in nature. This punctuates the urgency of addressing the critical knowledge gap in this domain. This project delivers on this need using a rigorous series of experimental particle tracking velocimetry (PTV) studies. The project will focus on three specific aims: (i) Investigate the role of axial flow factors including frequency of pulsation and input pulsatile waveform shape on transition to turbulence; (ii) Assess how the onset and development of transition to turbulence is sensitive to radial-flow instabilities such as pipe curvature or cross-sectional area occlusions or expansions; (iii) Develop analysis tools to estimate intermittency, transition progression, and expected fluctuation levels of key flow parameters (e.g., pressure) for any arbitrary flow. This effort will represent the first comprehensive suite of experimental studies in this domain as well as the first experimental studies to jointly and parametrically evaluate axial and radial flow factors that affect pulsatile transition. This project is expected to dramatically advance the current understanding of pulsatile transitional flow as well as establish translatable tools to enable future studies to quantify the presence and effects of this flow regime in any application area.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.

过渡和湍流脉动流已经在各种应用中观察到，包括生物医学流，例如通过心脏、主动脉和大脑的流动。过渡流引起压力和壁面剪应力等流动参数的显著波动，这可能导致重大的实际后果。例如，这些波动可以加速血管疾病的进展，包括心脏病、狭窄等;此外，它们还可使材料变弱直至失效，即，加速动脉瘤的破裂因此，为了准确地评估这些生物医学条件，重要的是要考虑和量化的过渡流效应的作用。不幸的是，在脉动流中向湍流的转变仍然是一个知之甚少的流态。因此，目前的研究往往忽略了过渡流的影响。因此，该项目的主要目的是提供脉动过渡流态的基本理解，以及建立能够估计其功能效果的通用工具。该项目还将侧重于扩大与实验流体动力学方法有关的培训和教育资源。此外，本发明还通过该项目收集的大量实验数据将公开提供，并用于建立一个全球可访问的难以获得的实验转捩和湍流数据库。该项目的目标是建立有关脉动管流中驱动转捩的机制的基础知识，并开发第一个类工具，能够估计不稳定性和过渡进程。迄今为止，探索这种流态的研究仅限于一次性的贡献，并产生了相互矛盾的结果。由于对这种流动状态缺乏共识和理解，越来越多的生物医学研究有争议地断言，平均雷诺数低至250的流动本质上是过渡性的。这突出表明了解决这一领域关键知识差距的紧迫性。该项目提供了这一需要使用一系列严格的实验粒子跟踪测速（PTV）的研究。该项目将侧重于三个具体目标：（一）调查轴向流动因素的作用，包括脉动频率和输入脉动波形形状在向湍流过渡方面的作用;（二）评估向湍流过渡的开始和发展如何对径向流动不稳定性敏感，如管道曲率或横截面积闭塞或扩张; ㈢开发分析工具，以估计关键流动参数（例如，压力）的任意流量。这项工作将代表在这一领域的第一个全面的实验研究套件，以及第一个实验研究，共同和参数化评估轴向和径向流动因素，影响脉动过渡。该项目有望极大地推进目前对脉动过渡流的理解，并建立可翻译的工具，使未来的研究能够量化这种流态在任何应用领域的存在和影响。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智力价值和更广泛的影响审查标准进行评估来支持。