Abstract

I will talk about the physics of multicomponent fluid mixing and phase separation, studied using (a) a time-dependent Ginzburg Landau formulation, and numerically implemented as a phase-field model and (b) a spectral closure model borrowed from turbulence theory. Due to external forcing, an initially quiescent system of two fluids exhibits highly nonlinear spatiotemporal evolution. The nonlinear mass and energy transport across the different length scales of the system during the mixing process will be discussed. I will show how these spatiotemporal dynamics exhibit universal characteristics independent of the system parameters, e.g., the magnitude of external forcing.  Such analytical and numerical study of mixing is essential to extract universal length and time scales in many industrial, as well as natural phenomena, e.g., in microfluidics (_{length scales in micrometers) or climate-science (e.g., mixing in global oceans}  kilometers). Capturing such universal features using analytical closure models (and also numerical simulations) is mathematically challenging, and rarely attempted before.   In the end, I will briefly talk about my work on fluid mixing in realistic global oceans, in particular, mixing due to ocean tides, and their impact on global climate variability.