Next generation of guiding questions for basic turbulent combustion research

Overview: A two-day workshop was held at the University of Michigan, Ann Arbor, MI, on June 9&10, 2014 to identify and compile research questions and needs to advance basic turbulent combustion research towards capabilities that allow predictive simulations at the design level for practical devices. Recognizing the state-of-the-art simulation capabilities and inherent limitations with computational resources the focus is on Large Eddy Simulations as a pathway to this goal. Five invited speakers presented aspects and questions on the state-of-the-art of turbulent combustion research in a public forum before the invited participants retreated for further analysis and discussion.

Intellectual Merit: The goal of fundamental research efforts in turbulent combustion is to identify and understand controlling basic principles – the physics and chemistry of turbulent combustion and use that knowledge to develop, test, and validate physics-based simulation tools that eventually will have predictive capability for design purposes. For practical reasons, largely given by limited computational capabilities, the description of some aspects of physics and chemistry and their interaction must often be simplified with models. Ideally, these models have input parameters that are (more or less) directly measurable in experiments to support rigorous and highly accurate validation work.

Large-Eddy-Simulation approaches have been advanced and are beginning to enter design-stage use in the community. It is true, though, that the need for and efforts in reducing the complexity and magnitude of the computational problem leads to the use of models. These models are typically systematically developed and validated for a limited set of conditions where the results of the simulations can show a high level of fidelity and agreement with experimental observations. The use of a simulation package for any other combustion problem might result in successful, unstable, unphysical, or predictions outside of the results from experimental observations. 

This workshop identified not only scientific and technical questions related to shortcomings in our current understanding of turbulent combustion, but also addressed procedural challenges. Key bottlenecks and research needs were addressed and described and it was emphasized that the conduct of research has to adapt to the complex nature of turbulent combustion by fostering collaborations and long-term funding horizons.

Broader Impact: The discussions and analysis conducted during the workshop were documented in a report, written by the collective of the participants. This publicly available report is expected to inform the community about research needs and future trends in combustion research. It may also help sponsoring bodies to identify and set funding priorities.