Applied Math Seminar Announcement

Turbulence is one of the most important, yet not fully understood, phenomenon in flow, spray and combustion processes; its accurate description is the key for the development of a successful simulation tool for reciprocating engines. A wide spread approach for the simulations of engines processes is the solution of the Reynolds/Favre-averaged conservation equations for mass, species, momentum, and energy. Associated with this averaging process are the turbulence-determining Reynolds fluctuation terms which have to be modeled in order to close this system.

A widely used class of turbulence models, based on the eddy-viscosity approach, utilizes two transport equations, one for the turbulence kinetic energy and one for the turbulence dissipation rate. These models have been successfully applied to a wide variety of steady state technical flows. However, one of their shortcomings is in rapidly varying transient flows, where the equilibrium turbulence hypothesis, which states that the turbulence production is balanced by the turbulence dissipation at any instant, is violated.

In this presentation, the delay between turbulence production and turbulence dissipation due to changes in the mean flow will be addressed. In particular, a correction for the turbulence dissipation rate, based on non-equilibrium turbulence considerations, will be investigated for reacting and non-reacting engine flows. Further, the effect of this dissipation rate correction on the prediction of the pollution formation will be discussed.