Speaker: Lin, Zhi (George) (IMA)
Title: Mathematical Models and Measures of Mixing.
Abstract: Mixing by stirring can be measured in a variety of ways including tracer particle dispersion, the scalar flux-gradient relationship, or via suppression of scalar density variation in the presence of inhomogeneous sources and sinks. The mixing efficacy of a flow is often expressed in terms of enhanced diffusivity and quantified as an effective diffusion coefficient. In this work we compare and contrast these various notions of effective diffusivity. Via thorough examination of a simple shear flow mixing a scalar sustained by a steady source-sink distribution, we explore apparent inconsistencies and propose a conceptual approach that captures some compatible features of these different models and measures of mixing.