Dissipation elements method provides analysis to understand turbulent non-premixed jet flames

A research team from universities and research centers in France and Germany has presented novel insight into the interaction between chemistry and turbulence by employing the method of dissipation elements in a non-premixed turbulent jet flame.

The researchers applied dissipation element analysis to a direct numeral simulation conducted on the JUQUEEN and SuperMUC supercomputers in, respectively, Julich and Garching, Germany. To start, the dissipation elements were computed on the mixture fraction field and parametrized by the arithmetic mean and difference between the endpoints. This parametrization introduced by the researchers provides a decomposition for turbulent reactive jet flows based on three selected regimes: a fuel rich regime, a fuel lean regime and a stoichiometric regime. The dissipation elements possess a two-point character, so the decomposition provided novel information about the local spatial structure of turbulent flames.

Modeling turbulent non-premixed flames requires a detailed knowledge about the local mixture fraction field. From their analysis of the formation and destruction of the mean gradient along the dissipation elements, the researchers showed that large gradients in the mixture fraction field occur at a small, finite length scale. The researchers connected this finding with chemistry and thereby were able to improve the understanding of the quenching process in turbulent flames.

By inspecting the inner structure of dissipation elements, the research team demonstrated that the method of dissipation elements provides an in-depth statistical characterization of flamelets, which in turn provides insightful knowledge regarding the interaction between chemistry and turbulence. This information is required for the modeling of turbulent non-premixed flames and should help engineers to better predict combustion and pollutant formation.

Source: “Dissipation element analysis of a turbulent non-premixed jet flame,” by Michael Gauding, Felix Dietzsch, Jens Henrik Goebbert, Dominique Thévenin, Abouelmagd Abdelsamie, and Christian Hasse, Physics of Fluids (2017). The article can be accessed at https://doi.org/10.1063/1.4991574 .