MRI: Development of a Multi-Camera Synthetic Aperture Technique for Measuring High-Speed, Unsteady, Three-Dimensional Velocity Flow Fields

这项重大研究仪器(MRI)为开发多相机合成孔径技术提供资金，用于测量高速、非稳定的三维速度场。杨百翰大学(BYU)的定量流体成像研究小组由三个实验室和三个PI组成，专注于实验流体动力学，因为它涉及众多多学科领域。实验室研究人员秉持的理念是，欢迎校园内外更广泛的大学社区内其他研究人员的参与。合并后的设施支持外部资助的研究项目，以及本科生和研究生实践教学实验室。这些实验室在研究项目上合作，共享资源，努力鼓励社区内的合作和同志情谊。该工具集中于可视化和量化流体现象，其中理解它们的行为对于理解它们的基本物理至关重要。这些现象包括但不限于人类呼吸道流动模式、昆虫飞行空气动力学、物体的水-出-入、多相流、疏水表面相互作用以及血液流动中的血栓生长。到目前为止，这些系统已经能够使用单摄像机2D PIV系统、热线风速测量或高速成像推断来研究。然而，该小组缺乏3D流动可视化系统和及时解析流场的能力。PI与麻省理工学院合作设计了一项新技术，使用几个高速摄像头从复杂的流体流动中提取速度。通过使用来自多个摄像机的多个视点，在三维中定量地测量了流动中的速度。杨百翰大学计划中的系统由10台高速摄像机组成，与高速激光同步，以捕获瞬时体积流场图像数据。通过在数字领域中的2D图像的重组，可以为每个时刻构建3D体积，从而在与视场(X-Y)一样深(Z)的体积中提供时间分辨信息，第三个优势是能够看到部分闭塞器周围，使我们能够分析密集播种的流动体积。这项技术有可能在未来几年成为确定流体流动速度的标准。该系统克服了目前3D PIV的一些缺点，如范围和分辨率有限，粒子播种密度低。与现成的高速断层PIV系统的成本大致相同，在开发一种新的最先进的系统/技术来帮助教育和激励新一代学生的同时，可以实现更大的平面外尺寸和更大的播种密度。流体成像小组进行的研究涉及多个学科，跨越学院、系和大学的界限，支持来自化学、机械和土木工程系以及物理、化学、生物和数学系的教职员工和学生。仪器的发展将扩大个人研究项目的影响，使人们能够更深入地了解正在研究的物理现象。这项技术还将提高对未来项目的了解，因为这项技术通过专门的网站、出版物和外联活动在科学界和工程界传播。3D合成孔径系统的开发也将使杨百翰大学内外的理工科其他方面受益，特别是本科生的教育和经验。该系统的许多开发人员和用户将是正在进行本科生研究的本科生。帮助开发这样的工具将使本科生能够获得通常为更高级的学位寻求者保留的教育机会。杨百翰大学在这方面是独一无二的，机构对本科生研究的重视程度很高。超过75%的机械工程专业毕业生正在攻读高级学位，使用建议系统的经验将为未来在研究生水平的研究和未来职业生涯中产生影响提供极好的培训。在杨百翰大学，最好的指导模式是将教职员工、研究生和本科生组成协同研究团队。这些设备还将整合到两个课程实验室，将课程扩展到高速、3D方法和现实世界应用，同时强调使用多学科方法研究困难的科学和工程问题的好处。最后，开发的系统将是一个具有深远的多学科应用的备受瞩目的系统，将通过校园内的外联活动，利用该系统吸引和招募代表性不足的学生进入STEM领域。

This Major Research Instrumentation (MRI) provides funding to develop a multi-camera synthetic aperture technique for measuring high-speed, unsteady, 3-D velocity flow fields. The quantitative fluids imaging research group at Brigham Young University (BYU) is a combination of three laboratories and three PIs focused on experimental fluid dynamics as it relates to a myriad of multidisciplinary areas. The laboratory researchers embrace a philosophy of welcoming participation from other researchers within the broader university community on and off campus. The combined facilities support externally funded research projects, as well as both undergraduate and graduate hands-on instructional laboratories. The laboratories work together on research projects and share resources in an effort to encourage collaboration and camaraderie within the community. The toolset is focused on visualizing and quantifying fluid phenomena where an understanding of their behavior is crucial to understanding their basic physics. The phenomena include, but are not limited to, human respiratory airway flow patterns, insect flight aerodynamics, water-exit-entry of objects, multiphase flows, hydrophobic surface interaction, and thrombosis growth in blood flow. Thus far these systems have able to be studied using single-camera 2D PIV systems, hot-wire anemometry, or inferences from high-speed imaging. However, the group lacks a 3D flow visualization system and the ability to resolve flow fields in time. A novel new technique designed by the PI, in collaboration with MIT, uses several high-speed cameras to extract velocities from complex fluid flows. Velocities in the flow are quantitatively measured in three dimensions by using several viewpoints from multiple cameras. The planned system at BYU consists of ten high-speed cameras synchronized with a high-speed laser to capture transient volumetric flow field image data. Through a recombination of the 2D mages in the digital realm a 3D volume can be constructed for each time instant, thus providing time-resolved information in volumes as deep (Z) as the field of view (X-Y), with the tertiary advantage of being able to see around partial occluders, allowing us to analyze densely seeded flow volumes. This technique has the potential to become the standard for determining velocities of fluid flows in the coming years. The system overcomes some of the current 3D PIV disadvantages such as limited range and resolution and low particle seeding densities. For roughly the same cost as an off-the-shelf high-speed tomographic PIV system, larger out-of-plane dimensions and larger seeding densities, can be achieved while developing a new state-of-the-art system/technology that helps educate and inspire a new generation of students.The research performed by the fluids imaging group is multidisciplinary and reaches across college, department, and university boundaries to support faculty, staff, and students from the Departments of Chemical, Mechanical and Civil Engineering as well as Physics, Chemistry, Biology and Mathematics. The instrumentation development will broaden the impact of the individual research projects by allowing the pursuit of a deeper understanding of the physical phenomena being studied. The technique will also improve understanding of future projects as the technique is disseminated among the scientific and engineering communities through a dedicated website, publication, and outreach activities. The development of the 3D Synthetic Aperture system will also benefit other aspects of science and engineering on and off the BYU campus, particularly undergraduate student education and experience. Many of the developers and users of the system will be undergraduates doing undergraduate research. Helping to develop a tool like this one will enable undergraduates to receive educational opportunities normally reserved for more advanced degree seekers. BYU is unique in this regard and a large institutional emphasis on undergraduate research exists. Over 75 percent of the graduates of the Mechanical Engineering program pursue advanced degrees, and experiences using the proposed system will provide excellent training for future impact in graduate level research and future careers. At BYU the best mentoring model combines faculty, graduate students, and undergraduates in synergistic research teams. The equipment will also be integrated into two course laboratories to extend the curriculum into high-speed, 3D methods and real world applications, while emphasizing the benefit of using multidisciplinary approaches to study difficult science and engineering problems. Finally, the developed system will be a high-profile system with far reaching multidisciplinary applications that will be leveraged to attract and recruit underrepresented students to STEM fields through outreach activities on campus.