FLUID DYNAMICS REVIEWS SEMINAR SERIES
Speaker: Michael Mueller, Ph.D.
Department of Mechanical and Aerospace Engineering
TURBULENT COMBUSTION MODELING: THE COMBUSTION PERSPECTIVE VERSUS THE TURBULENCE PERSPECTIVE
March 16, 2017 | 3:00 PM | DeWalt Seminar Room, 2164 Martin Hall
Turbulent combustion modeling is a challenging multi-physics, multi-scale modeling problem. Both turbulence and combustion are already difficult multi-scale problems, and the combination of the two brings in new interactions across various length and time scales that fundamentally change both the combustion processes and the turbulence. This seminar will focus on turbulent combustion modeling from two distinct perspectives: that of combustion and that of turbulence.
A significant portion of the effort in turbulent combustion modeling has focused on the combustion perspective. From this perspective, the modeling challenge is in describing the unresolved, small-scale details of the combustion processes and the many chemical species involved. Models for the combustion processes can be divided into two distinct classes subject to an inherent trade-off: models that are very general in their description of the underlying combustion processes but computationally intensive versus models that make very constraining assumptions about the underlying combustion processes but are computationally efficient. In the latter class of models, the combustion processes are typically constrained to low-dimensional manifolds derived by assuming combustion occurs in a single asymptotic mode: premixed flames, nonpremixed flames, or homogeneous reactions. For multi-modal combustion, the current state-of-the-art is to apply the “best” asymptotic model locally, but recent LES results indicate the inherent shortcomings of this approach. A new, generalized combustion model will be presented that breaks this inherent trade-off, leveraging a more detailed manifold description that can capture not only the asymptotic modes of combustion but also intermediate regimes.
A far less significant effort has been devoted in turbulent combustion modeling to the turbulence perspective. In fact, most of the turbulence models applied in turbulent combustion modeling are simply adapted from incompressible turbulence, despite the fact that theoretical arguments have been made that turbulence is strongly affect by combustion in certain regimes. Recent DNS results confirm these theoretical arguments and the regimes in which turbulence is affected by the heat release from combustion. Budget analyses from the DNS data are used to identify the physical phenomena that need to be included in new turbulence models, and one possible way forward is proposed.
More info at: www.enme.umd.edu/events/fluid-dynamics-review-seminars