Budroni Marcello A, Polo Alessandro, Upadhyay Virat, Bigaj Adam, Rongy Laurence
Department of Chemistry and Pharmacy, University of Sassari, Via Vienna 2, 07100 Sassari, Italy.
Nonlinear Physical Chemistry Unit, Service de Chimie Physique et Biologie Théorique, Université Libre de Bruxelles, CP 231 - Campus Plaine, 1050 Brussels, Belgium.
J Chem Phys. 2021 Mar 21;154(11):114501. doi: 10.1063/5.0042560.
Spatio-temporal oscillations can be induced under batch conditions with ubiquitous bimolecular reactions in the absence of any nonlinear chemical feedback, thanks to an active interplay between the chemical process and chemically driven hydrodynamic flows. When two reactants A and B, initially separated in space, react upon diffusive contact, they can power convective flows by inducing a localized variation of surface tension and density at the mixing interface. These flows feedback with the reaction-diffusion dynamics, bearing damped or sustained spatio-temporal oscillations of the concentrations and flow field. By means of numerical simulations, we detail the mechanism underlying these chemohydrodynamic oscillations and classify the main dynamical scenarios in the relevant space drawn by parameters ΔM and ΔR, which rule the surface tension- and buoyancy-driven contributions to convection, respectively. The reactor height is found to play a critical role in the control of the dynamics. The analysis reveals the intimate nature of these oscillatory phenomena and the hierarchy among the different phenomena at play: oscillations are essentially hydrodynamic and the chemical process features the localized trigger for Marangoni flows unstable toward oscillatory instabilities. The characteristic size of Marangoni convective rolls mainly determines the critical conditions and properties of the oscillations, which can be further tuned or suppressed by the buoyancy competition. We finally discuss the possible experimental implementation of such a class of chemo-hydrodynamic oscillator and its implications in fundamental and applied terms.
在间歇条件下，即使没有任何非线性化学反馈，由于化学过程与化学驱动的流体动力流之间的积极相互作用，普遍存在的双分子反应也能引发时空振荡。当最初在空间上分离的两种反应物A和B在扩散接触时发生反应，它们可以通过在混合界面处引起表面张力和密度的局部变化来驱动对流。这些流动与反应扩散动力学相互反馈，产生浓度和流场的阻尼或持续时空振荡。通过数值模拟，我们详细阐述了这些化学流体动力学振荡的潜在机制，并在由参数ΔM和ΔR绘制的相关空间中对主要动力学场景进行分类，这两个参数分别控制表面张力和浮力驱动的对流贡献。发现反应器高度在动力学控制中起着关键作用。分析揭示了这些振荡现象的内在本质以及不同现象之间的层次关系：振荡本质上是流体动力学的，而化学过程是导致对振荡不稳定的马兰戈尼流的局部触发因素。马兰戈尼对流卷的特征尺寸主要决定了振荡的临界条件和特性，浮力竞争可以进一步调节或抑制这些振荡。我们最后讨论了这类化学流体动力学振荡器的可能实验实现及其在基础和应用方面的意义。
