Interaction of Turbulence, Chemistry, and Radiation in Strained Nonpremixed Flames

Chun Sang Yoo and Hong G. Im
University of Michigan
Yi Wang and Arnaud Trouvé
University of Maryland

Recent advances in the parallel computing technology have enabled high-end direct numerical simulations of laminar and turbulent reacting flows to unravel fine-scale physics with utmost realism and accuracy. To achieve this goal successfully, it is essential to develop reliable numerical algorithms that are robust, stable, and free from artificial dissipation. Furthermore, efficient implementation of advanced physical models is needed in order to allow quantitative investigation of many challenging issues that are arising from the complex interaction between turbulence, chemistry, and heat transfer. This paper provides an overview of recent progress in the SciDAC Project entitled “Terascale High-Fidelity Simulations of Turbulent Combustion with Detailed Chemistry.” In particular, two major accomplishments are presented and discussed: (a) As for the computational aspects, it was recognized that many existing techniques to treat inflow and outflow boundary conditions for compressible flow simulations suffered from spurious errors when applied to highly turbulent reacting flow problems. Upon careful examination, the sources of these problems have been identified and an improved characteristic boundary condition strategy has been developed. The new method has been applied to various test problems, thereby demonstrating that the improved boundary conditions can successfully reproduce complex combustion events in a finite domain size with desired accuracy and stabililty. (b) As a science application, more advanced physical models for soot formation and radiative heat transfer have been developed in order to provide fundamental understanding of the interaction among turbulence, chemistry and radiation. We have performed several parametric simulations of two-dimensional ethylene-air nonpremixed counterflow flames interacting with counter-rotating vortex pairs and injected turbulent flows to investigate transient dynamics of soot formation process. Detailed analysis on the transient characteristics of soot behavior is discussed.