Topology of dynamically passive scalar fields in isotropic homogeneous turbulence

摘要

Transport of scalars by turbulent fluid motion is of fundamental importance and is encountered in applications such as pollutant formation, mass and heat transfer and chemical reactions. The physics of many of these applications is extremelycomplex and not well understood due to the intriguing complex topology of the fluid motions and scalar fields. In this paper, a new formulation is proposed to study the detailed topology of diffusing scalars and their relationship to the turbulent flowtopology. Direct numerical simulations (DNS) are used to study those topologies in homogeneous isotropic turbulence, using an object-oriented code (Crespo 1994).Yoda et. at (Yoda 1994) used a modified concentration gradient field to investigate the topology of the scalar field by calculating the invariants of &{sup}2{sub}c/(&x{sub}ix{sub}j), where c is the scalar concentration. This formulation has two seriousdrawbacks: it cannot be cast in terms of a dynamical system evolution, and no clear physical interpretation emerges from it.