Measuring rotations of 3D printed particles in turbulent fluid flow

测量湍流中 3D 打印颗粒的旋转

• 批准号: 1508575
• 负责人: Greg Voth
• 金额: $ 36.12万
• 依托单位: Wesleyan University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-06-01 至 2020-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1508575&HistoricalAwards=false
• 关键词: Measuring; rotations; 3D; printed; particles

Nontechnical Abstract:When particles are transported in a turbulent fluid flow, their motion is strongly affected by their shape. Most previous work on particle motion in turbulence has considered the simplest case which is spherical particles, but an understanding of non-spherical particle motion is necessary to understand many important situations including ice crystals in clouds, the processing of wood fibers in paper making, and many biological organisms such as plankton whose motion in turbulent flow is affected by their non-spherical shape. Recently, it has become clear that the dynamics of anisotropic particles also offer a powerful new way to understand some fundamental properties of the fluid motion in turbulence such as vortex stretching. In this project, we use 3D printers to create particles with a wide range of shapes and track the particle motion in a turbulent water flow using multiple high speed video cameras. We have identified a special particle shape which we call a chiral dipole that should preferentially rotate in one direction when it is placed in a random turbulent environment. Such a particle can extract energy from specific scales of the turbulent flow. We also will measure the rotational motion of particles formed from several symmetric thin rods connected in the center. These particles can be made in a wide range of sizes and allow measurement of the amount of rotational energy at different scales in the turbulent flow. We will study particles that deform in the fluid flow, and develop new methods of fabricating small particles in custom designed shapes. This work will provide valuable foundational science for work on engineering and environmental applications involving anisotropic particles in turbulence. It will also provide a new and intuitive way to measure some of the most fundamental processes in turbulence including vortex stretching and the rotational energy that exists at different scales in turbulent flows. Methods for measuring forces on particles and fabricating small particles with customized shapes should also find use far beyond our work. Education and research training are central to this project, which will support the mentoring of a postdoctoral scientist, a graduate student, and undergraduates in research. The project also supports the PI's work co-directing the Wesleyan Science Outreach program.Technical Abstract: The dynamics of anisotropic particles in turbulent fluid flows are important in many applications including paper making, icy clouds, and locomotion of micro-organisms in environmental flows. Recently, it has become clear that the dynamics of anisotropic particles also offer a powerful new window into fundamental properties of the small scales of turbulent flows. In this project, we use 3D printed particles to experimentally measure the rotation and alignment of anisotropic particles of a wide variety of sizes and shapes in turbulent fluid flow. Chiral dipoles formed from two opposite handed helices joined in the center should have a preferential rotation direction in an isotropic turbulent flow. This should provide an elegant way to observe a fundamental property of turbulence: on average material lines and vortices are being stretched by the flow. As chiral dipoles are stretched, they should exhibit a solid body rotation vector whose projection onto the chiral dipole vector has a non-zero mean. Particles will also be printed with four arms in tetrahedral symmetry and a wide range of sizes in order to observe the distribution of rotational energy as a function of scale in a turbulent flow. The moments of the solid body rotation rate as a function of particle size may show power law scaling across an inertial range with corrections to the mean field theory scaling exponents due to turbulent intermittency. The forces acting on arms of particles can be measured from the bending of the arms. Particles will be printed from flexible polymers and tracked in highly viscous fluids to determine the feasibility of measuring forces this way. Finally, we will explore the use of two-photon stereo-lithography for fabricating particles with much higher spatial resolution allowing much smaller particles to be printed. Education and research training are central to this project, which will support the mentoring of a postdoctoral scientist, a graduate student, and undergraduates in research. The project also supports the PI's work co-directing the Wesleyan Science Outreach program.

非技术摘要：当颗粒在湍流中输送时，它们的运动受到其形状的强烈影响。 大多数以前的工作在湍流中的粒子运动已经考虑了最简单的情况下，这是球形粒子，但非球形粒子运动的理解是必要的，以了解许多重要的情况，包括冰晶在云中，木材纤维的加工造纸，和许多生物有机体，如浮游生物，其运动在湍流中受到其非球形形状的影响。 最近，人们已经清楚，各向异性粒子的动力学也提供了一个强大的新方法来理解湍流中的流体运动的一些基本性质，如涡流拉伸。 在这个项目中，我们使用3D打印机创建各种形状的颗粒，并使用多个高速摄像机跟踪湍流水流中的颗粒运动。 我们已经确定了一种特殊的粒子形状，我们称之为手征偶极子，当它被放置在一个随机的湍流环境中时，它应该优先在一个方向上旋转。 这种粒子可以从特定尺度的湍流中提取能量。 我们还将测量由几个中心连接的对称细棒形成的粒子的旋转运动。 这些颗粒可以制成各种尺寸，并允许测量湍流中不同尺度的旋转能量。 我们将研究在流体流动中变形的颗粒，并开发制造定制设计形状的小颗粒的新方法。 这项工作将提供有价值的基础科学的工程和环境应用的工作，涉及湍流中的各向异性颗粒。 它还将提供一种新的和直观的方式来测量湍流中的一些最基本的过程，包括涡流拉伸和湍流中不同尺度下存在的旋转能量。 测量颗粒上的力和制造具有定制形状的小颗粒的方法也应该远远超出我们的工作范围。 教育和研究培训是这个项目的核心，它将支持博士后科学家，研究生和本科生的研究指导。 该项目还支持PI的工作，共同指导卫斯理科学推广program.Technical Abstract：湍流中各向异性颗粒的动力学在许多应用中非常重要，包括造纸，冰云，以及环境流动中微生物的运动。 最近，人们已经清楚，各向异性粒子的动力学也提供了一个强大的新窗口的基本性质的小尺度湍流。 在这个项目中，我们使用3D打印颗粒来实验测量湍流中各种尺寸和形状的各向异性颗粒的旋转和排列。 在各向同性湍流中，由两个在中心连接的相反手螺旋形成的手征偶极子应该具有优先旋转方向。 这应该提供了一个优雅的方式来观察湍流的基本属性：平均而言，材料线和漩涡被流动拉伸。 当手征偶极子被拉伸时，它们应该表现出固体旋转矢量，该固体旋转矢量在手征偶极子矢量上的投影具有非零均值。 颗粒也将被打印成四面体对称的四个臂和各种尺寸，以观察旋转能量的分布作为湍流中尺度的函数。 作为颗粒尺寸的函数的固体旋转速率的时刻可以显示在惯性范围内的幂律缩放，由于湍流的不稳定性，平均场理论缩放指数的校正。 作用在颗粒臂上的力可以从臂的弯曲来测量。 粒子将从柔性聚合物中打印出来，并在高粘性流体中跟踪，以确定以这种方式测量力的可行性。 最后，我们将探索使用双光子立体光刻来制造具有更高空间分辨率的颗粒，从而允许打印更小的颗粒。 教育和研究培训是这个项目的核心，它将支持博士后科学家，研究生和本科生的研究指导。 该项目还支持PI共同指导卫斯理科学外展计划的工作。