RUI: Experimental Studies of Active Mixing in Extended Fluid Systems

非技术摘要本项目的实验探索了流体流动对“活性”物质的影响，如游动的有机体和移动的反应前沿。流体流动在自然界和技术中无处不在，包括在生物体中;在河流，湖泊和海洋中;在大气和恒星中;在许多工业过程中;甚至在社会中的人的“流动”中。这些实验测试了以下预测：流体混合可以使微生物菌落同步生长，类似于海洋中藻类的快速“开花”;流体中的混合模式可以影响表面生物膜的形成;游泳和流体流动的结合可以导致“混乱”的轨迹;流动可以增强--有时也会抑制--游动微生物群和反应前沿的传播。这些实验的结果可以帮助解释藻类水华是如何形成的，以及疾病是如何在移动的人群中传播的;对主动混合的理解也有助于“自组装”微结构的发展。 所有的研究都是与本科生一起完成的，给他们的经验在他们作为科学家的发展中起着重要的作用。技术摘要本项目的实验研究层流对消耗能量的活性杂质的影响，导致相对于流体的运动。活性杂质是（a）自我推进的微生物，例如游动细菌和藻类;和（B）繁殖的化学反应前沿。流动包括涡链和涡列流动、交叉通道中的双曲线流动、时间相关通道流动和空间无序流动。PI小组以前的实验已经证明，“燃烧不变流形”和“游泳不变流形”阻止了层流中活性杂质的运动。我们将扩展这些研究，探索运输和图案形成的活性杂质的距离大于典型的流量规模。实验将调查：（1）层流混合对微生物菌落生长的影响，包括有和没有趋化性和趋光性;（2）混沌流体混合对生物膜形成的影响;（3）反应前沿和微生物集合体前缘的大规模传播;（4）流动中活性杂质的混沌运动，其中被动混合是非混沌的;（5）层流中活性杂质的长程输运;以及（6）多代选择如何增强某些游泳协议，以响应流体混合。该奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查支持的搜索.

Non-Technical AbstractExperiments in this project explore the effects of fluid flows on “active” agents such as swimming organisms and moving reaction fronts. Fluid flows are everywhere in nature and in technology, including in living organisms; in rivers, lakes and oceans; in the atmosphere and in stars; in numerous industrial processes; and even in “flows” of people in society. These experiments test predictions that fluid mixing can synchronize the growth of microbial colonies, similar to the rapid “blooming” of algae in the oceans; that mixing patterns in the flow can affect the formation of biofilms on surfaces; that the combination of swimming and the fluid flow can result in “chaotic” trajectories; and that flows can enhance – and sometimes inhibit -- the spreading of groups of swimming microbes and of reaction fronts. The results from these experiments could help explain how algae blooms form and how diseases spread in moving populations; an understanding of active mixing could also help in the development of “self-assembled” microstructures. All of the research is done with undergraduate students, giving them experiences that play an important role in their development as scientists.Technical AbstractThe experiments in this project study the effects of laminar flows on active impurities that consume energy, resulting in motion relative to the fluid. The active impurities are (a) self-propelled microbes, such as swimming bacteria and algae; and (b) propagating chemical reaction fronts. The flows include vortex chain and vortex array flows, hyperbolic flows in a cross-channel, time-dependent channel flows, and spatially-disordered flows. Previous experiments by the PI’s group have demonstrated that “burning invariant manifolds” and “swimming invariant manifolds” block the motion of active impurities in laminar flows. We will extend these studies to explore transport and pattern formation of active impurities over distances larger than typical flow scales. The experiments will investigate: (1) the effects of laminar mixing on the growth of microbial colonies, both with and without chemo- and phototaxis; (2) the effects of chaotic fluid mixing on biofilm formation; (3) large-scale propagation of reaction fronts and the leading edges of microbial ensembles; (4) chaotic motion of active impurities in flows where passive mixing is non-chaotic; (5) long-range transport of active impurities in laminar flows; and (6) how selection over multiple generations enhances certain swimming protocols in response to the fluid mixing.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.