Intruder dynamics in fluid saturated granular medium

由固体颗粒和流体组成的介质广泛存在于地质、石油开采、化工和食品加工等行业。在这些情况下，入侵者的运动，例如章鱼在海床上的挖洞或移动，目前很难预测。无论入侵者是比固体颗粒密度更大的刚性物体，还是机器人或蠕虫等活动物体，都是如此。这项研究将开发一套模型，根据入侵者的物理属性和介质的物理属性来预测入侵者的详细运动。此外，还将使用三维成像技术进行实验，允许同时测量入侵者的运动以及周围颗粒和流体的运动。实验和模型将首先聚焦于球形入侵者，然后扩展到杆状和多连杆机器人入侵者。这些可能用于探测海洋沉积物的机器人的设计规则将通过研究淡水蠕虫的运动来制定。最终，研究结果将应用于工业中湿颗粒材料的高效处理，以及能够在复杂环境中移动的机器人的开发。该项目将在一个专注于STEM的协作环境中为处于其教育事业不同阶段的学生提供研究经验。研究了干燥颗粒材料中的入侵者运动，以了解动力系统和分离机制中的非遍历行为。然而，对流体饱和颗粒介质中的入侵者动力学的了解，对于更广泛的自然和工业系统来说是非常重要的，但在很大程度上是不发达的。从颗粒和悬浮物研究中得到的作为无量纲惯性数和粘性数函数的介质的流变学描述将与低雷诺数流体动力阻力理论相结合来描述入侵者在多相颗粒系统中的运动。将进一步发展紧密耦合的荧光标记内部成像技术，并用于在单颗粒水平上测量颗粒和液体相的重排。详细测量入侵者的形状和方位相关的阻力，并将观测到的阻力与介质的微观力学联系起来，将使建立湿颗粒介质中主动和被动入侵者动力学的基本流变学模型成为可能。项目活动还将支持一系列教育活动，包括促进本科生和研究生实验室研究经验，以及针对在校学生和公众的外展活动。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Media composed of solid grains and fluids occur in geology, oil recovery, and chemical and food processing industries. The motion of an intruder in these situations, for example, the burrowing or locomotion of an octopus through the sea bed, is currently difficult to predict. This is true whether the intruder is a large, rigid object that is denser than the solid grains or an active object such as a robot or worm. This research will develop a set of models that predict the detailed motion of intruders as a function of their physical properties and those of the medium. In addition, experiments will be performed with three-dimensional imaging techniques that allow simultaneous measurement of the intruder motion and the motion of the surrounding grains and fluid. The experiments and models will focus first on spherical intruders, and then extend to rods and multi-link robot intruders. Design rules for these robots, which might be used to probe marine sediments, will be developed by studying the motion of freshwater worms. Ultimately, the results will be applied to efficient processing of wet granular materials in industry and the development of robots that can move through complex environments. The project will provide research experience for students at various stages of their educational careers in a collaborative environment focused on STEM.Intruder motion in dry granular materials has been studied to understand non-ergodic behavior in dynamical systems and segregation mechanisms. However, an understanding of intruder dynamics in fluid saturated granular medium, important to an even wider range of natural and industrial systems, is largely underdeveloped. Rheological descriptions of the medium developed recently as a function of dimensionless inertial and viscous numbers from granular and suspensions research will be combined with low-Reynolds number hydrodynamic resistive force theory to describe the motion of the intruder in multi-phase particulate systems. Closely coupled fluorescence-tagged internal imaging techniques will be further developed and used to measure the rearrangements of the granular and fluid phase at the single-grain level. Detailed measurement of the shape and orientation dependent drag of the intruder combined with the connection of the observed drag to the micromechanics of the medium will enable the development of a fundamental rheology model of active and passive intruder dynamics through wet granular medium. The project activities will also support a range of educational activities including enabling undergraduate and graduate laboratory research experience, and outreach activities targeting school students and members of the public.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.