Chemistry in Flow: Amplification versus Extinction

化学反应与传输过程的耦合在生物学、工程学和大气科学等众多学科中都很重要。许多反应表现为自催化，在这种反应中，反应的产物，即活化剂，催化自己的生成。自催化作用为化学信号的放大和传播提供了重要的机制。化学和水流结合在一起，形成了从微观到宏观长度尺度上的生物模式，从变形体绒泡菌中细胞内容物的移动(流动)到海洋流动中浮游生物群体的生长(水华)。尤其重要的是反应在无阻水流中得以维持的条件。自催化反应通常以全有或全无的方式响应；反应被放大，可能导致空间分布的反应热点，或被气流熄灭。已经证明，即使是湍流也包含一定程度的相干，例如涡旋，这可能为物种的局部混合和反应放大创造条件。然而，尽管理论正在迅速涌现，但几乎没有实验数据来区分它们。这个项目的目的是通过一个紧密耦合的实验和理论研究计划来解决这种真空问题。这里提出的跨学科研究将考察自催化化学和流动的相互作用，重点是微观结构流动对宏观化学活性的影响。我们的目标是进行受控实验室研究，以量化相干流动对反应放大的作用。我们的研究将为了解复杂流动体系中的化学反应动力学提供一个新的视角。在本项目中，我们将：(A)使用磁共振成像(MRI)显示管流、旋涡和混沌流场中的自催化化学反应，并量化反应被放大的条件；(B)开发自催化化学反应与相干流场的耦合理论和模型(C)表征相干流动环境中空间有序的出现。本项目将产生：(1)流动中化学反应的磁共振研究实验规程MRI是唯一能够同时可视化化学反应和反应介质的探针传输性质的设备。磁共振成像还能够探测使用光学方法无法到达的流动几何图形中的化学放大。这项技术将为我们提供化学波的3D图像，并允许我们将实验实现的流动转化为反应的数值模拟。核磁共振还提供了利用磁场最终操纵局部化学结构的可能性。(2)将自催化化学反应与二维和三维流场相结合的计算模型使我们能够产生实验上难以获得的数据，预测复杂系统的行为，并指导实验研究。白玫瑰网格(http://www.wrgrid.org.uk/))是一个跨越利兹、约克和谢菲尔德大学的高性能计算设施，是一个卓越的电子科学中心。利兹大学的研究人员利用在伯明翰产生的实验数据来验证、开发和改进模型，是利用这一计算设施的理想选择。

The coupling of chemical reaction with transport processes is important in a wide variety of disciplines such as biology, engineering and atmospheric science. Many reactions display autocatalysis, in which a product of the reaction, the activator, catalyses its own production. Autocatalysis provides an important mechanism for the amplification and propagation of a chemical signal. Chemistry and flow combine to give rise to biological pattern formation on microscopic to macroscopic length scales, from the movement of cellular contents (streaming) in the amoeboid physarum to the growth of plankton colonies (blooming) in oceanic flows. Of particular importance are the conditions for which a reaction is sustained in open flow. Autocatalytic reactions generally respond in an all-or-nothing fashion; the reaction is amplified, possibly resulting in spatially-distributed reaction hot spots , or extinguished by the flow. It has been demonstrated that even turbulent flows contain some degree of coherence, such as vortices, that may create conditions for localised mixing of species and reaction amplification. However, while theories are emerging rapidly there is little experimental data to distinguish between them. The aim of this project is to address this vacuum via a closely coupled experimental and theoretical programme of research.The interdisciplinary research proposed here will examine the mutual interaction of autocatalytic chemistry and flow, focussing on the influence of micro-structured flow on macroscopic chemical activity. Our goal is to produce controlled laboratory studies to quantify the role of coherent flow on reaction amplification. Our research will provide an insight to the dynamics of chemical reaction in complex flow systems. In this project we will:(a) Use Magnetic Resonance Imaging (MRI) to visualise autocatalytic chemical reaction in pipe-flow, vortices and chaotic flow fields and quantify the conditions for which the reaction is amplified(b) Develop theory and models coupling autocatalytic chemical reaction with coherent flow fields(c) Characterise the emergence of spatial order in coherent flow environmentsThis project will produce:(1) Experimental protocols for MRI investigation of chemical reaction in flowMRI is uniquely able to simultaneously visualise chemical reaction and probe transport properties of the reaction media. MRI is also able to probe chemical amplification in flow geometries inaccessible using optical methods. This technique will provide us with 3D images of chemical waves, and allow us to transfer experimentally-realised flows into numerical simulations of the reaction. MRI also presents the possibility for the eventual manipulation of the localised chemical structures using magnetic fields. (2) Computational models coupling autocatalytic chemical reaction with 2D and 3D flow fieldsModels allow us to generate data that might be difficult to obtain experimentally, predict how complex systems will behave and steer experimental investigations. The White Rose Grid (http://www.wrgrid.org.uk/) is a high performance computing facility that spans Leeds, York and Sheffield Universities and is an e-Science Centre of Excellence. The Leeds investigators are ideally placed to utilise this computational facility, using experimental data generated in Birmingham to validate, develop and improve the models.