CAREER: Simultaneous Measurement of Wall Deformation and 3-D Flow Structures for Flow-Structure Interaction Investigations

CBET-0748149盛理解和模拟流动的流体和高度灵活的固体边界之间的复杂相互作用在工程和生物学的许多应用中都是主要的挑战。当体流是时间相关的或脉动的时，这个问题特别难建模。在心血管疾病和阿尔茨海默病的研究中，使用生物表面的流量控制或与顺应性表面的噪声消除受到了不同研究社区的相当大的关注。尽管计算方法和理论发展迅速，但可变形表面和近壁流动之间的复杂相互作用仍然只有部分了解，阻碍了开发准确模型的努力。详细的实验数据对于指导和验证建模工作至关重要。PI的目标是利用最近开发的尖端3D成像技术--数字全息显微镜(DHM)--所收集的动力，开发一种直接观察和量化界面上复杂相互作用的技术。DHM将同时测量其附近的壁面变形和三维速度场。同时测量是通过记录和跟踪两组粒子实现的，一组嵌入变形壁中，另一组位于变形壁附近的流动中。DHM是唯一能够在3-D中执行这项任务的设备。随后，该技术将扩展到测量沿变形壁面的压力和应力分布。为了提供对样品区域的畅通无阻的观察，测量将在一个特殊的光学折射率匹配设备中进行。这项研究包括仪器的开发，所有接口的指数匹配设施和方法。这项测量技术将用于研究脉动近壁流动与可变形表面相互作用的三种情况：均匀柔顺表面上的脉动流动，旨在识别刚性和柔顺壁面之间流动结构、壁面应力和压力分布的异同；柔度突然变化的表面，旨在研究柔度不均匀在近壁流动结构产生中的作用及其对压力和壁应力分布的影响；以及可变形液滴在柔顺表面上的运动，旨在量化液滴、周围流体和可变形表面之间的相互作用。为这一阶段开发了具有嵌入粒子的折射率匹配液滴。对各种流体特征进行条件采样，如近壁相干结构、壁面应力分布、以壁面变形为条件的压力，将获得由变形引起的流动特性变化。人们还可以通过调节某些流动特性和直接测量表面力来评估流动对壁面变形的贡献。分析将提供流体动力载荷和地表变形之间的双向耦合机制。这一测量有望帮助理解这一在工程学和生物学中都有广泛应用的基本主题。它将为社会带来好处，例如通过准确的死亡诊断和患者特定的风险评估来改善医疗保健。这项研究的影响预计是广泛的。通过将DHM技术扩展到完全量化三维近壁流动和壁面变形，特别是瞬时压力和壁面应力分布，该技术有可能改变研究领域的面貌，并可能导致突破性的发现。研究和教育活动的结合将为成功的、全面的学术生涯奠定基础。本科生和研究生将参与这项研究，这项工作的跨学科性质将反映在PI的教学和建议方法上。目前的教育计划的重点是通过开发一种可以使用现成的手机摄像头记录数字全息图的工具包来扩大数字全息术的普及率。该软件将可供下载，并将通过Facebook、MySpace等青少年流行网站进行广告宣传，以接触到大量受众，并招收不同类型的新工科学生。

CBET-0748149ShengUnderstanding and modeling of complex interactions at the interface between a flowing fluid and a highly flexible solid boundary present major challenges with many applications in engineering and biology. This problem is particularly difficult to model when the bulk flow is time dependent or pulsatile. Flow control using biological surfaces or noise cancellation with compliant surfaces has received considerable attention from various research communities for studying cardiovascular disorders and Alzheimer neurological degeneration. Despite rapid advances in computational methods and theoretical development, complex interactions between deformable surfaces and near-wall flow remain only partially understood, hampering efforts to develop accurate models. Detailed experimental data are essential for guiding and validating modeling efforts. The PI's goal is to harness the momentum gathered during recent development of a cutting-edge 3-D imaging technique, digital holographic microscopy (DHM), to develop a technique to observe and quantify complex interactions at the interface directly. DHM will measure the wall deformation and 3-D velocity field near it simultaneously. The concurrent measurements are achieved by recording and tracking two groups of particles, one embedded in the deforming wall and the other located in the flow near it. DHM is uniquely capable of performing this task in 3-D. Subsequently, the technique will be extended to measure the distributions of pressure and stresses along the deforming wall. To provide unobstructed view on sample area, measurements will be performed in a special optically index-matched facility. This research includes development of instrumentation, an index-matched facility and methodology for all interfaces. This measurement technique will be applied to study three cases of interactions of a pulsating near wall flow with a deformable surface: Pulsating flow over homogeneous compliant surface intended to identify the similarities and differences in flow structure, wall stress and pressure distributions between rigid and compliant walls; a surface with a sudden change in compliance, intended to examine the role of compliance inhomogeneity in the generation of near wall flow structures and their impact on pressure and wall stress distribution; and motion of deformable droplets over a compliant surface, intended to quantify interactions among droplets, surrounding fluids and a deformable surface. Index-matched droplets with embedded particles with be developed for this phase. Conditional sampling over wide range of fluid features such as near wall coherent structure, wall stress distribution, pressure conditioned on wall deformation will obtain deformation-induced changes in flow characteristics. One can also assess the contribution of flow to wall deformation by conditioning upon certain flow characteristics, and from directly measuring surface forces. Analysis will provide two-way coupling mechanism between hydrodynamic loading and surface deformation. This measurement is expected to help understand this fundamental topic with wide range of applications in both engineering and biology. It will provide benefits to society, such as better healthcare through accurate decease diagnosis and patient specific risk assessment. The impacts of the research are expected to be broad. By extending DHM technique to fully quantify 3-D near wall flow and wall deformation, especially instantaneous pressure and wall stress distributions, the technique has a potential of changing the landscape of the research field and may lead to groundbreaking discoveries. The combination of research and educational activities will lay the foundations for a successful, well-rounded academic career. Undergraduate and graduate students will be involved in the research, and the interdisciplinary nature of this work will be reflected in the PI's approach to teaching and advising. The present educational plan is focused on expanding the popularity of digital holography by developing a kit that can record digital holograms using readily available cell-phone cameras. The software will be available for download, and will be advertised through teen popular websites like Facebook, MySpace, to reach a large audience and to recruit new diverse engineering students.