2. Dissipation Element Analysis of Inert and Reacting Turbulent Flows

Dissipation elements provide a procedure for compartmentalizing scalar fields into physically meaningful sub-units which provides a direct measure for turbulent scales. Furthermore, dissipation elements enable a variety of additional ways of investigating non-local effects in reacting and non-reacting turbulent flows. After the underlying physical ideas of dissipation elements are explained and a parameterization of dissipation elements is defined, the method of detecting dissipation elements with gradient trajectories is explained and physical and numerical prerequisites are presented. Common characteristics of dissipation elements are interpreted and compared for a large range of selected reacting and non-reacting flow configurations. To provide the reader with a degree of familiarity, dissipation element statistics are then related to more commonly used methods of obtaining statistics. The additional benefit of using the dissipation element analysis in free shear flows is highlighted by using it as an alternative way of identifying turbulent core regions. Next, a dissipation element-based procedure for the local investigation of the turbulence–combustion interaction in the context of non-premixed flames is presented. The chapter is concluded with the application of a dissipation element statistics-based modeling procedure for computational fluid dynamics of a passenger car diesel engine, employing the previously gained insight into the structure of turbulent scalar fields.