UNS: Collaborative Research: Multiscale interactions between active particles and stratified fluids during collective vertical migration

CBET - 1510607/1510615 PI：Dabiri，John/Meiburg，EckartThis合作项目使用实验和数值模拟来研究水中小型游泳生物的集体运动。该项目的基本假设是，许多小生物体的集体运动可以引起比生物体本身大得多的长度尺度上的流体运动。 研究人员将专注于分层流体层的运动，这在海洋中很常见，其中顶部流体层通常比更深的流体层更温暖，更咸。 分层可导致引起流体运动的不稳定性，但游动生物体的存在可改变运动开始的条件，并影响由运动引起的详细流动模式和流体混合。 虽然该研究以海洋中的运动为例，但从该项目中获得的见解将适用于其他颗粒和多相系统。 两名调查人员都将让高中生、本科生和研究生参与该项目。 该项目的成果将用于外联工作，以吸引来自传统上在科学和工程领域代表性不足的群体的学生参与研究。该提案的目标是通过实验和数值方法解决分层层中多尺度、多体、流体-结构相互作用的基本问题。 这些实验将使用一种独特的系统，该系统可以在受控的实验室环境中通过趋光性产生浮游生物的按需垂直迁移。 激光制导系统将控制游泳速度和游泳者集体运动的间距。 二维粒子成像测速仪将用于测量游泳运动产生的流动。 在该项目中实施的数值方法能够模拟大量的游泳生物体，其保真度足以研究近场和远场流的细节。 数值模拟将有助于测试集体游泳运动通过修改热量和盐度的有效扩散率来驱动大规模对流从而诱导双扩散对流的可能性。

CBET - 1510607/1510615PI: Dabiri, John/Meiburg, EckartThis collaborative project uses experiments and numerical simulation to investigate the collective motion of small swimming organisms in water. The hypothesis underlying the project is that the collective motion of many small organisms can induce fluid motion over length scales that are much larger than the organism itself. The investigators will focus on motion in stratified fluid layers, which are commonly found in the ocean, where the top fluid layer usually is warmer and saltier than deeper fluid layers. The stratification can lead to an instability that induces fluid motion, but the presence of the swimming organisms may change conditions for the onset of the motion and affect detailed flow patterns and fluid mixing that result from the motion. Although the research focuses on motion in the ocean as an example, the insights gained from the project will apply to other particulate and multiphase systems. Both investigators will involve high school students, undergraduates and graduate students in the project. Results from the project will be used in outreach efforts to engage in the research students from groups that are traditionally underrepresented in science and engineering.The objective of the proposal is to address experimentally and numerically the fundamental questions of multi-scale, many-body, fluid-structure interactions in stratified layers. The experiments will use a unique system that can produce on-demand vertical migrations of plankton via phototaxis in a controlled laboratory setting. A laser-guidance system will control swimming speed and swimmer spacing in collective motions. Two-dimensional particle imaging velocimetry will be used to measure flows generated by the swimmers' motion. The numerical methods implemented in the project are capable of simulating large numbers of swimming organisms with fidelity sufficient for studying details of both the near- and far-field flows. Numerical simulations will help test the possibility that collective swimming motions drive large-scale convection by modifying effective diffusivities of heat and salinity so as to induce double-diffusive convection.