Chemo-Hydrodynamic Kelvin-Helmholtz Instability

Hydrodynamic instabilities, such as the Saffman-Taylor or Rayleigh-Taylor Instability, have long been associated with chemical reactions [1]. Recently, we, for the first time, identified the Kelvin-Helmholtz Instability as a Chemo-Hydrodynamic Instability that can be induced by a simple (A+B→C)-type reaction [2]. This reaction alters the viscosity profile of layered fluids within a channel flow. In our study, two viscosity-matched reactants, A and B, flow axially in a layered manner, producing a more viscous product, C, in a two-dimensional channel. When we perturb this flow with a sine wave, intriguingly, a Kelvin-Helmholtz type pattern forms at one front while the other remains stable. This perturbation amplification arises from oscillatory streamlines exhibiting a phase lock system. Moreover, increasing the log-mobility ratio (R_c) intensifies the perturbation amplitude. Furthermore, the location of the interfacial region near the bottom wall results in streamlines developing hump-like structures and becoming out of phase, causing the regular pattern to become irregular. Additionally, at higher Reynolds numbers (Re), we observe the formation of ligament-type waves, resembling patterns seen in earlier experimental observations [3]. In the presentation, we will discuss when the dominance of convection and diffusion affects the flow's stability.



[1] De Wit, Ann. Rev. Fluid Mech. 52, 531 (2020).

[2] Maharana et al., J. Fluid Mech. 955, A36 (2023).

[3] Hu and Cubaud, Phys.Rev. Lett. 121, 044502 (2018).