Chemo-Hydrodynamic Patterns and Instabilities

Abstract

By modifying a physical property of a solution like its density or viscosity, chemical reactions can modify and even trigger convective flows. These flows in turn affect the spatiotemporal distribution of the chemical species. A nontrivial coupling between reactions and flows then occurs. We present simple model systems of this chemo-hydrodynamic coupling. In particular, we illustrate the possibility of chemical reactions controlling or triggering viscous fingering, Rayleigh–Taylor, double-diffusive, and convective dissolution instabilities. We discuss laboratory experiments performed to study these phenomena and compare the experimental results to theoretical predictions. In each case we contrast the chemo-hydrodynamic patterns and instabilities with those that develop in nonreactive systems and unify the different dynamics in terms of the common features of the related spatial mobility profiles.

Physicochemical hydrodynamics of droplets out of equilibrium

“…This perspective review convey ideas, rather than delve into detailed technical aspects or be encyclopedic. For these aspects we refer to specialized review articles on certain aspects, such as the one by Cates and Tjhung on binary fluid mixtures [2], by Lauga and Powers on swimmers [3], by Maass et al on swimming droplets [4], by Moran and Posner and by Golestanian on phoretic self-propulsion [5,6], by Manikantan and Squires on surfactant dynamics [7], by Cazabat & Guéna [8] and Erbil [9] on evaporation of pure liquid sessile droplets, by Sefiane on patterns from drying drops [10], by Lohse and Zhang on surface nanobubbles and nanodroplets [11], by Jain on single-drop microextraction [12], by de Wit on chemo-hydrodynamic patterns and instabilities [13], etc.…”

Rayleigh-Taylor Instability: A Status Review of Experimental Designs and Measurement Diagnostics

“…The developments in modeling and simulations in RTI can be found in a companion review by Schilling [33], a review of the theoretical modeling techniques and issues related to variable-density flows with large thermal and density fluctuations can be found in [34]. No attempt is also made to cover the experiments related to the formation of RTI in the highenergy-density regime or RTI due to change in viscosity or chemical reactions; the reader can find those in other recent reviews [35,36]. Furthermore, RTI in solids is also not discussed and can be found in reviews by Zhou [21,22].…”

Scalings of the mixing velocity for buoyancy-driven instabilities in porous media

“…A subsequent choice of their initial concentrations fixes then the buoyancy ratio and thus the dynamic density jump controlling the growth of the mixing length of the buoyancy-driven fingers. This control strategy, illustrated here for differential diffusion effects, can easily be adapted to other processes (like non-ideal mixing or chemical reactions for instance) that are able to induce non-monotonic density profiles (De Wit 2020) or to multispecies stratifications. Moreover, as the control depends only on local adverse density jumps, which are obtained analytically from the diffusion equation and not from the flow equations, it will be interesting to test if the scalings demonstrated here using porous medium flows have equivalent robust scalings for other flow equations as well.…”

“…The RT, DD and DLC instabilities have been shown recently to arise genuinely in stratifications of reactive solutions as they involve different solutes with different diffusion coefficients (Lemaigre et al. 2013; De Wit 2020). This has motivated us to revisit the scalings of the RT instability in two-species stratifications of non-reactive fluids, as well as its possible interaction with the DD and DLC differential diffusion modes (Trevelyan et al.…”