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Physical Sub-Model Development for Turbulence Combustion Closure


OBJECTIVE: Development of physics-based models and associated modules and libraries for turbulence combustion closure for combustion regimes of relevance to the Air Force. DESCRIPTION: Turbulent combustion phenomena are crucial for the prediction of the stability and performance of many practical combustion systems. This topic is focused on the development of physics-based turbulent combustion closure schemes for pre-mixed, non-premixed and partially premixed flames for all flow and chemistry regimes. A number of turbulent combustion models have been proposed in the literature ranging from the early eddy break-up models to work involving flamelets, PDF-based approaches, the Linear-Eddy Model, and so on [e.g., Refs. 1-5]. Despite this progress, the general state-of-the-art of turbulent combustion models in widely available reacting flow codes remains inadequate. Of particular interest is the formulation of turbulent combustion models in the context of high-resolution Detached Eddy Simulations (DES) or Large Eddy Simulations (LES) with a focus on gas-phase mixing and combustion. Also of interest are methods for handling detailed finite-step chemical kinetics in the context of large-scale computations such as flamelet libraries and/or in-situ adaptive tabulation (ISAT) of finite-rate kinetics. Development of new promising approaches, as well as the enhancement of existing methods, are appropriate with an emphasis being given to fundamental physics-based models. Underlying model assumptions such as incompressibility should be evaluated for consistency for the intended combustion regimes. Model predictions must be validated against relevant data, including those being obtained within related AFOSR programs. A further requirement is that the model development be made modular by the specification of standardized Application Programming Interfaces (or API"s), which would enable the models to be available as plug-in libraries to appropriate turbulent reacting flow codes of relevance for Air Force applications. These interfaces should be fashioned to be independent of code-specific data structures in order to maintain generality. The availability of standard LES or DES sub-grid models and finite-rate chemical kinetics can be assumed to exist in the parent code, but all other aspects of the turbulent combustion models would be enabled through the new module or modules. PHASE I: Demonstrate turbulent combustion model capability that shows promise in the context of DES and LES calculations. Evaluate model assumptions for consistency for the intended combustion regimes. Develop prototype modules with well-characterized and generalized interfaces. PHASE II: Further develop/enhance the target turbulent combustion model capability. Perform detailed validation for test cases of relevance to the Air Force. Demonstrate the modular approach for the turbulent combustion sub-models in candidate turbulent reacting flow code or codes of relevance to the DoD. PHASE III: Turbulent combustion phenomena are of key relevance to the performance of military propulsion systems, including liquid rockets, solid rockets, gas turbines, and augmentors, and to non-military systems such as space launch systems, aircraft engines, land-based power systems, and automotive engines. REFERENCES: 1. N. Peters, Turbulent Combustion, Cambridge University Press, (2000). 2. T. Poinsot and D. Veynante, Theoretical and Numerical Combustion, 2nd ed., R.T. Edwards (2005). 3. Kerstein, A., A Linear Eddy Model of Turbulent Scalar Transport and Mixing, Combustion Science and Technology, Vol. 60, pp. 391. 4. L. Lu, S. R, Lantz, Z. Ren, S. B. Pope, Computational Efficient Implementation of Combustion Chemistry in Parallel PDF Calculations, Journal of Computational Physics, Vol. 228, Issue 15, pp. 5490-5525 (2009). 5. B. Franzelli, E. Riber, L.Y.M. Gicquel, and T. Poinsot, Large Eddy Simulation of combustion instabilities in a lean partially premixed swirled flame. Combustion and Flame, 159(2):621 - 637, 2012.
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