Budroni M A, Upadhyay V, Rongy L
Nonlinear Physical Chemistry Unit, Faculté des Sciences, Université libre de Bruxelles (ULB), CP231, 1050 Brussels, Belgium.
Department of Chemistry and Pharmacy, University of Sassari, Via Vienna 2, Sassari 07100, Italy.
Phys Rev Lett. 2019 Jun 21;122(24):244502. doi: 10.1103/PhysRevLett.122.244502.
We present a new mechanism through which chemical oscillations and waves can be induced in batch conditions with a simple A+B→C reaction in the absence of any nonlinear chemical feedback or external trigger. Two reactants A and B, initially separated in space, react upon diffusive contact and the product actively fuels in situ convective Marangoni flows by locally increasing the surface tension at the mixing interface. These flows combine in turn with the reaction-diffusion dynamics, inducing damped spatiotemporal oscillations of the chemical concentrations and the velocity field. By means of numerical simulations, we single out the detailed mechanism and minimal conditions for the onset of this periodic behavior. We show how the antagonistic coupling with buoyancy convection, due to concurrent chemically induced density changes, can control the oscillation properties, sustaining or suppressing this phenomenon depending on the relative strength of buoyancy- and surface-tension-driven forces. The oscillatory instability is characterized in the relevant parametric space spanned by the reactor height, the Marangoni (Ma_{i}) and the Rayleigh (Ra_{i}) numbers of the ith chemical species, the latter ruling the surface tension and buoyancy contributions to convection, respectively.
我们提出了一种新机制，通过该机制，在间歇条件下，仅通过简单的A + B→C反应，在不存在任何非线性化学反馈或外部触发因素的情况下，就能诱导出化学振荡和波。两种反应物A和B最初在空间上是分开的，在扩散接触时发生反应，产物通过局部增加混合界面处的表面张力，在原位对流马兰戈尼流中积极提供燃料。这些流动又与反应 - 扩散动力学相结合，诱导化学浓度和速度场的阻尼时空振荡。通过数值模拟，我们找出了这种周期性行为开始的详细机制和最小条件。我们展示了由于同时发生的化学诱导密度变化，与浮力对流的拮抗耦合如何控制振荡特性，根据浮力和表面张力驱动力的相对强度维持或抑制这种现象。振荡不稳定性在由反应器高度、第i种化学物质的马兰戈尼数（Ma₁）和瑞利数（Ra₁）所跨越的相关参数空间中进行表征，后者分别决定了表面张力和浮力对对流的贡献。
