Chemistry in Flow: Amplification versus Extinction

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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.