Berkeley Fluids Seminar
University of California, Berkeley
Bring your lunch and enjoy learning about fluids!
October 23, 2013
Prof. Ali Mani (Mechanical Engineering, Stanford)
Direct Numerical Simulation of Electrokinetic Instability and Hydrodynamic Chaos Near Ion-Selective Surfaces
Electrokinetic phenomena (e.g. in electrochemical or microfluidic systems) are often described by the Poisson-Nernst-Planck and Navier-Stokes equations. However, the mainstream models describing solutions to these equations are based on asymptotic simplifications including bulk electroneutrality, quasi-steadiness, and/or quasi-equilibrium. In this presentation we will demonstrate the need for the development of specialized algorithms for simulation of electrokinetic phenomena, similar to the tools that have been traditionally used for simulation of turbulent flows. At the core of our investigation we consider ion transport through an ion-selective surface as a model problem with applications in electrochemistry, such as water purification, electrolysis and lab-on-a-chip system. We will present results from our research and show that direct calculations, without asymptotic simplifications, can predict electrokinetic chaos with multi-scale vortices consistent with recent experimental observations. These calculations require resolving a wide range of spatio-temporal scales using unsteady solvers and often need massively parallel computational resources. Similar to turbulence simulations and in contrast to the mainstrean commercial software, non-dissipative numerical discretization is crucial for effective preservation of physics of chaotic vortices. We will discuss how development of such high-fidelity tools can lead to fundamental understanding of complex effects in electrokinetic systems and facilitate their design and optimization.