Overview

Mastering transport and mixing phenomena is key to the optimization of many industrial processes, including single- and multiphase chemical transformations, aeronautics and turbomachinery. However, analyzing the time-dependent flow fields based on primary variables such as velocity is usually not sufficient to capture the underlying mechanisms.

Lagrangian coherent structures (LCS) and their quantitative interpretation via finite-time Lyapunov exponents (FTLE) offer an alternative route with some unique advantages for revealing the coherent structures of a given flow field, which exhibits an ordered behavior characterized by the repelling and attracting material surfaces. In principle, these surfaces behave like dynamic boundaries that organize the main flow behavior, providing an intuitive way to explore and understand the governing phenomena, even for very complex problems such as vortex motion, interfacial transport and micro-mixing.

At ITS, we have developed our own post-processing tool, postAtom, to explore the large-scale data generated by turboSPH simulations, velocity field measurements and grid-based Eulerian solvers. A unique feature of postAtom is the highly efficient GPU implementation of FTLE field computations, which enables real-time interactive analysis of FTLE fields in 3-D datasets. Such analysis allows us to identify mixing patterns on different length scales together with their temporal evolution, leading to a unique insight into the local phenomena and the possibility to track the influence of geometric variations.