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A Computationally Efficient “Turnkey” Approach Turbulent Combustion Modeling

Event Type: 
Date and Time: 
Friday, November 15, 2019 - 16:30
CTR Conference Room 103
Event Sponsor: 
Parviz Moin, Director of Center for Turbulence Research
Professor Michael E. Mueller

Turbulent combustion is an extremely challenging “multi-multi” problem: multi-physics, multi-scale, and multi-species. Since not all scales of turbulence and combustion can be resolved in DNS for practical conditions of interest, models are required for the unresolved turbulent combustion processes in LES and RANS. However, the large number of thermochemical scalars required to describe combustion chemistry (potentially hundreds or thousands of chemical species) means that the unresolved state-space that needs to be modeled is extremely high-dimensional. Turbulent combustion models can generally be divided into two distinct classes based on how this dimensionality challenge is addressed. In the first class of models, no attempt is made to reduce the dimensionality of the unresolved state-space (“brute-force” models). While very general, these approaches are extremely computationally intensive and realistically impractical. Conversely, in the second class of models, the dimensionality of the unresolved state-space is reduced by a priori presuming that combustion occurs in one of the asymptotic “modes” of nonpremixed combustion, premixed combustion, or homogeneous autoignition, each of which can be described by simple one-dimensional manifold equations. While this results in a substantial reduction in computational cost, these models are not generally applicable to “multi-modal” combustion processes characteristic of practical systems. In this seminar, recent efforts to overcome this fundamental modeling trade-off will be discussed. Our new turbulent combustion modeling framework is both computationally efficient and extremely general, requiring no a priori knowledge about the underlying combustion processes in order to reduce the dimensionality of the unresolved state-space. The new approach relies on two game-changing components: (1) generalized two-dimensional manifold equations capable of describing arbitrary “multi-modal” combustion processes and (2) sensible computational algorithms that shift away from unnecessary precomputation and high-dimensional pretabulation toward ‘just-in-time’ computation and adaptive tabulation. Preliminary application with LES to canonical turbulent flames will be briefly discussed.

Michael E. Mueller is an Associate Professor in the Department of Mechanical and Aerospace Engineering at Princeton University, an associated faculty member in the Princeton Institute for Computational Science and Engineering, an associated faculty member in the Andlinger Center for Energy and the Environment, and the Director of the Graduate Certificate in Computational Science and Engineering. He received a BS degree in mechanical engineering from The University of Texas at Austin in 2007, a MS degree in mechanical engineering from Stanford University in 2009, and a PhD degree in mechanical engineering from Stanford University in 2012 before moving to Princeton in 2012. In 2017 he was recognized with an award through the Young Investigator Program (YIP) of the Army Research Office (ARO), and he currently serves as Associate Editor for the Journal of Engineering for Gas Turbines and Power. His expertise is the computational modeling of turbulent reacting flows. Current research interests within his group includes multi-modal turbulent combustion, combustion-influenced turbulence, pollutant emissions, and uncertainty quantification.