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

CBET - 1510607/1510615PI: Dabiri, John/Meiburg， eckart这个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。这个项目的基本假设是，许多小生物的集体运动可以引起比生物本身大得多的长度尺度上的流体运动。调查人员将把重点放在分层流体层的运动上，这种流体层通常在海洋中发现，在海洋中，顶层流体层通常比深层流体层更温暖、更咸。分层会导致流体运动的不稳定性，但游动生物的存在可能会改变运动开始的条件，并影响运动产生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。两位研究者都将让高中生、本科生和研究生参与这个项目。该项目的成果将用于推广工作，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。本提案的目的是通过实验和数值方法解决分层层中多尺度、多体流固相互作用的基本问题。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按需垂直迁移的浮游生物。激光制导系统将控制游泳速度和游泳者在集体运动中的间距。二维粒子成像测速法将用于测量游泳者运动产生的流量。该项目中采用的数值方法能够模拟大量游动的生物，其保真度足以研究近场和远场流动的细节。数值模拟将有助于验证集体游泳运动通过改变热量和盐度的有效扩散系数从而诱导双扩散对流来驱动大规模对流的可能性。

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.