Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session D26: Reactive Flows II: Turbulent Combustion Modelling |
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Chair: Tarek Echekki, North Carolina State University Room: 31B |
Sunday, November 18, 2012 2:15PM - 2:28PM |
D26.00001: Numerical Investigation of a Piloted Premixed Jet Burner Yuntao Chen, Matthias Ihme Premixed and partially premixed combustion technologies have the potential of reducing pollutant emissions and enhancing the overall combustion efficiency. However, the successful implementation of these technologies in practical systems requires a thorough understanding of the underlying combustion-physical phenomena. To predict partially premixed combustion, a three-stream progress-variable model has been developed. This model is applied to large-eddy simulations of the piloted premixed jet burner experiment of Dunn et al., and configurations PM1-\{50,100,150\} are considered. Comparisons with measurements for all three configurations are presented, and it is shown that this model is capable of capturing the characteristics of the flow-field, temperature, and compositional field. [Preview Abstract] |
Sunday, November 18, 2012 2:28PM - 2:41PM |
D26.00002: Verification and Validation of a Chemical Reaction Solver Coupled to the Piecewise Parabolic Method Nitesh Attal, Praveen Ramaprabhu, Jahed Hossain, Varad Karkhanis, Sukesh Roy, James Gord, Mesbah Uddin We present a detailed chemical kinetics reaction solver coupled to the Piecewise Parabolic Method (PPM [1]) embedded in the widely used astrophysical FLASH [2] code. The FLASH code solves the compressible Euler equations with a directionally split, PPM with Adaptive Mesh Refinement (AMR). The reaction network is solved using a library of coupled ODE solvers, specialized for handling stiff systems of equations. Finally, the diffusion of heat, mass, and momentum is handled either through an update of the fluxes of each quantity, or by directly solving a diffusion equation for each. The resulting product is capable of handling a variety of physics such as gas-phase chemical kinetics, diffusive transport of mass, momentum, and heat, shocks, sharp interfaces, multi-species mixtures, and thermal radiation. We will present results from verification and validation of the above capabilities through comparison with analytical solutions, and published numerical and experimental data. Our validation cases include advection of reacting fronts in 1-D and 2D, laminar premixed flames in a Bunsen burner configuration, and shock-driven combustion.\\[0pt] [1] P. Colella and P. R. Woodward, J. Comput. Phys. 54, 174-201 (1984). [2] B. Fryxell et al., Astrophys. J., Suppl. Ser. 131, 273 (2000). [Preview Abstract] |
Sunday, November 18, 2012 2:41PM - 2:54PM |
D26.00003: Nonlinear Principal Component Analysis for Combustion Large-Eddy Simulation Hessam Mirgolbabaei, Tarek Echekki Moment-based methods have been widely used in turbulent combustion modeling, by transporting a set of moments and reconstructing thermo-chemical scalars' statistics. Instead of ad hoc strategies to select these moments, more optimal moments have been proposed recently using principal component analysis (PCA). However, it is not evident that the linear PCA alone can represent the non-linear nature of the space representing thermo-chemical scalars' statistics effectively. As a nonlinear alternative to the classical PCA in which the linear transformation of the original space is constructed, kernel PCA(KPCA) is adapted in the present work, in that the original space is mapped into a Feature space where the intrinsic dimensionality can be linearly extracted. Re parameterization is performed based on one-dimensional turbulence (ODT) for the implementation of KPCA, for implementation in a novel large-eddy simulation (LES) approach, as well. This involves the solution of LES on a coarse-grid and fine-grained ODT solutions embedded in the LES domain. Parameters from the KPCA analysis can be used to evaluate key terms in the transport equation for the moments. These terms are tabulated using artificial neural networks (ANN). [Preview Abstract] |
Sunday, November 18, 2012 2:54PM - 3:07PM |
D26.00004: A Novel Principal Component Analysis-Based Acceleration Scheme for LES-ODT: An A Priori Study Tarek Echekki, Hessan Mirgolbabaei A parameterization of the composition space based on principal component analysis (PCA) is proposed to represent the transport equations with the one-dimensional turbulence (ODT) solutions of a hybrid large-eddy simulation (LES) and ODT scheme. An a priori validation of the proposed approach is implemented based on stand-alone ODT solutions of the Sandia Flame F flame, which is characterized by different regimes of combustion starting with pilot stabilization, to extinction and reignition and self-stabilized combustion. The PCA analysis is carried out with a full set of the thermo-chemical scalars' vector as well as a subset of this vector. The subset is made up primarily of major species and temperature. The results show that the different regimes are reproduced using only three principal components for the thermo-chemical scalars based on the full and a subset of the thermo-chemical scalars' vector. Reproduction of the source term of the principal component represents a greater challenge. It is found that using the subset of the thermo-chemical scalars' vector both minor species and the first three principal components source terms are reasonably well predicted. [Preview Abstract] |
Sunday, November 18, 2012 3:07PM - 3:20PM |
D26.00005: LES-ODT Simulations of Turbulent Reacting Shear Layers Andreas Hoffie, Tarek Echekki Large-eddy simulations (LES) combined with the one-dimensional turbulence (ODT) simulations of a spatially developing turbulent reacting shear layer with heat release and high Reynolds numbers were conducted and compared to results from direct numerical simulations (DNS) of the same configuration. The LES-ODT approach is based on LES solutions for momentum on a coarse grid and solutions for momentum and reactive scalars on a fine ODT grid, which is embedded in the LES computational domain. The shear layer is simulated with a single-step, second-order reaction with an Arrhenius reaction rate. The transport equations are solved using a low Mach number approximation. The LES-ODT simulations yield reasonably accurate predictions of turbulence and passive/reactive scalars' statistics compared to DNS results. [Preview Abstract] |
Sunday, November 18, 2012 3:20PM - 3:33PM |
D26.00006: Novel Strategies for Coupling 3D LES with ODT Solutions Based on Wavelet and Assimilation Methods Yuqiang Fu, Tarek Echekki The LES-ODT approach is a multi-scale framework for the simulation of turbulent reacting flows. It is based on the implementation of two solutions: 1) LES for continuity and momentum and 2) ODT for momentum and reactive scalars. The coupling is based on upscaling, which filters the ODT solution for the filtered density onto LES and upscaling, which corrects the ODT momentum solution to make it consistent with the LES solution. Wavelet-based downscaling uses the compound wavelet matrix method to substitute large-scale physics from LES onto the ODT solution, while maintaining the ODT residual sub-grid scale contribution intact. A Kalman filter based upscaling is used obtain a smooth filtered density field from ODT. The present study demonstrates the use of the upscaling and downscaling methods for a LES-ODT simulation of a reacting flow. [Preview Abstract] |
Sunday, November 18, 2012 3:33PM - 3:46PM |
D26.00007: FDF Simulation of a Realistic Gas Turbine Combustor Naseem Ansari, Patrick Pisciuneri, Peter Strakey, Peyman Givi The unstructured scalar filtered mass density function (SFMDF) is employed for the large eddy simulation (LES) of a realistic swirl flame combustor. This is the PRECCINSTA experimental burner from the German Aerospace Center (DLR) [1]. This burner is a reasonable representation of an industrial gas turbine combustor and has been the subject of broad experimental and computational investigations. To keep the geometrical complexity of the burner intact, the fuel injection holes are meshed along with radial swirler vanes and the mixing zone prior to the nozzle exit. Combustion chemistry is modeled with a reduced mechanism featuring $16$ species and $12$ reaction steps. The simulated data are analyzed by comparison of the Reynolds-averaged statistics with experimental data and show excellent agreement. This demonstrates the capability of FDF for LES of complex flows, and warrants future applications of the methodology for LES of practical combustor configurations. \\[4pt] [1] W. Meier, P. Weigand, X.R. Duan, and R. Giezendanner-Thoben. Detailed characterization of the dynamics of thermoacoustic pulsations in a lean premixed swirl burner. \textit{Combust. Flame}, \textbf{150}:2-26, (2007). [Preview Abstract] |
Sunday, November 18, 2012 3:46PM - 3:59PM |
D26.00008: Petascale FDF Large Eddy Simulation of Reacting Flows Patrick Pisciuneri, S. Levent Yilmaz, Peyman Givi A novel computational methodology, termed ``Irregularly Portioned Lagrangian Monte Carlo-Finite Difference'' (IPLMCFD) is developed for large eddy simulation (LES) of turbulent flows. This methodology is intended for use in the filtered density function (FDF) formulation and is particularly suitable for simulation of chemically reacting flows on massively parallel platforms. The IPLMCFD allows for tremendous improvements in scalability, and is the key enabler of petascale computations. The methodology is employed for LES of several flame configurations. [Preview Abstract] |
Sunday, November 18, 2012 3:59PM - 4:12PM |
D26.00009: Filtered Density Function for Large Eddy Simulation of Local Entropy Generation in Turbulent Reacting Flows Mehdi Safari, M. Reza H. Sheikhi Analysis of local entropy generation is an effective means to investigate sources of efficiency loss in turbulent combustion from the standpoint of the second law of thermodynamics. A methodology, termed the ``entropy filtered density function'' (En-FDF), is developed for large eddy simulation (LES) of turbulent reacting flows to include the transport of entropy. The filtered form of entropy transport equation contains several unclosed entropy generation terms that contribute to efficiency losses in turbulent combustion. The closure is provided by the En-FDF, which embodies the complete statistical information about entropy variations within the subgrid scale. An exact transport equation is developed for the En-FDF. The unclosed terms in this equation are modeled by considering a system of stochastic differential equations. The modeled En-FDF transport equation is solved by a Lagrangian Monte Carlo method. The En-FDF is applied to a turbulent shear layer and validated by comparing with results obtained from direct numerical simulation of the same layer. The methodology is also employed to study local entropy generation in turbulent flames. The results are compared with the experimental data. [Preview Abstract] |
Sunday, November 18, 2012 4:12PM - 4:25PM |
D26.00010: LES-CMC Approach for Dilute Reacting Sprays Santanu De, Boxiong Chen, Seung Hyun Kim Large eddy simulation (LES) of dilute reacting spray jets is carried out using the conditional moment closure (CMC) method. Over the past few decades, LES-CMC has shown its capabilities in describing turbulence-chemistry interactions in gas-phase non-premixed reactive flows. In this study, we address some modeling complexities arising due to the presence of multiple phases. Most of the previous CMC studies have either neglected the effects of evaporation on conditional moments or used simplified models. Only recently, fundamental equations for the CMC modeling of spray combustion have been derived. The resulting CMC equations contain several correlation terms associated with phase changes. Here, an attempt is made to model those unclosed terms. A stochastic method is used to generate the SGS fluctuations in gas-phase reactive scalars consistent with the framework of a mixture-fraction-based combustion model. The SGS fluctuations of the gas-phase temperature and composition, seen by droplets, are used to refine the estimates of the interphase heat/mass transfer rates. Results from the LES-CMC approach for both the gas- and liquid phases are extensively validated against available experimental measurements. [Preview Abstract] |
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