Mechanical & Aerospace Engineering

Biography

Biography: Evgeny A. Demekhin

Abstract

The advent of micro-, nano- and biotechnologies in the last decade has spurred numerous new and active research areas, in particular, problems of electrokinetics. Other than the practical importance of these effects is a theoretical interest to these problems: study of the space charge in the electric double-ion layer is a fundamental problem of modern physics, first addressed by Helmholtz. We shall focus on an often-ignored phenomenon: the underlying very rich hydromechanics. The relevant hydrodynamics involves micro-scale vortices, vortex instabilities and even turbulence like eddy fluctuations whose vortex pairing dynamics create a range of vortex sizes, all at miniscule Reynolds numbers. Singularities, instabilities, turbulence, continuum of length scales, self-similar solution, vortex pairing etc are among the investigated phenomena. Despite of their micro and nano length scales, these instabilities and bifurcations exhibit all the hall marks of other classical hydrodynamic instabilities – a subharmonic cascade, wide-band fluctuation spectrum and coherent-structure dominated spatio-temporal dynamics. We shall present our results for the one-phase electrokinetic instability near charge-selective surfaces, influence to this instability of the surface profile, the effect of a coupling between electrokinetic phenomena and the surface hydrophobicity, Joule heating, geometric confinement etc. Unstable two-phase liquid-gas flows with a mobile surface charge finalize our investigation. The problems are studied from the viewpoint of hydrodynamic stability and bifurcation theory using sophisticated asymptotic methods and direct numerical simulations.