Past Event: Oden Institute Seminar

Towards DNS of Turbulent Combustion in Complex Flows at the Exascale

Jacqueline Chen, Senior Scientist, Combustion Research Facility, Sandia National Laboratories

Abstract

Direct numerical simulation methodology and computing power have progressed to the point where it is feasible to perform DNS in mildly complex geometries representative of flow configurations encountered in practical combustors. These complex flows encompass effects of mean shear, flow recirculation, and wall boundary layers together with turbulent fluctuations which affect entrainment, mixing and combustion. Examples of recent DNS studies with complex flows relevant to gas turbine and internal combustion engines will be presented and the turbulence-chemistry interactions described. These include sequential reheat combustion in the presence of mixed combustion modes – hydrogen/air autoignition and flame propagation in a rectangular duct-in-a-duct configuration, stabilization of a turbulent premixed ethylene/air flame behind a backwards facing step, turbulent piloted premixed methane/air jet flames at high Karlovitz conditions, and multi-injection mixing and ignition of prevaporized n-dodecane jets at diesel conditions. In many of these complex flows there are regions of low-intensity turbulence with mean recirculation, flame-wall interaction in boundary layers, and shear generated turbulence interacting with ignition kernels or a flame brush. The mean shear and boundary layer provide sources of turbulence generation which interact with the flame brush. These complex flows may induce turbulence-chemistry interactions distinct from those observed in isotropic decaying or forced homogeneous turbulence. New numerical diagnostics have been developed to delineate the mixed combustion regimes based on extensions of the chemical explosive mode analysis (CEMA). Finally, through the DOE Exascale Computing Project, prospects for computation of complex flows at the exascale with in situ data driven reduced order surrogate models and anomaly detection will be discussed. BIO Jacqueline H. Chen is a Senior Scientist at the Combustion Research Facility at Sandia National Laboratories. Prior to 2018, she was a Distinguished Member of Technical Staff. She has contributed broadly to research in petascale direct numerical simulations (DNS) of turbulent combustion focusing on fundamental turbulence-chemistry interactions. These benchmark simulations provide fundamental insight into combustion processes and are used by the combustion modeling community to develop and validate turbulent combustion models for engineering CFD simulations. In collaboration with computer scientists and applied mathematicians she is the founding Director of the Center for Exascale Simulation of Combustion in Turbulence (ExaCT). She leads an interdisciplinary team to co-design DNS algorithms, domain-specific programming environments, scientific data management and in situ uncertainty quantification and analytics, and architectural simulation and modeling with combustion proxy and production applications. She received the DOE INCITE Award in 2005, 2007, 2008-2014, the Asian American Engineer of the Year Award in 2009, and the Sandia OE Adams Award in 2012. She is a member of the DOE Advanced Scientific Computing Research Advisory Committee (CASCARA) and Subcommittees on Exascale Computing, and Synergies of Big Data and Exascale. She is the editor of Flow, Turbulence and Combustion, the co-editor of the Proceedings of the Combustion Institute, volumes 29 and 30, and is a member of the Board of Directors of the Combustion Institute. Her areas of research interests are in the development and application of massively parallel petascale direct numerical simulations (DNS) of turbulent combustion with complex chemistry. These DNS are used to understand fundamental chemistry-turbulence interactions in combustion, and to develop and validate predictive combustion models ultimately used to design efficient and clean engines reliably burning a diverse range of fuels, from bio-derived and synthesized fuels to fossil fuels from evolving feeds. Note: Please join this Zoom seminar online with the "Audio Only" function (no video)