Download or read book A Reacting Jet Direct Numerical Simulation for Assessing Combustion Model Error written by Bryan William Reuter and published by . This book was released on 2021 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: The simulation of turbulent combustion systems is a vital tool in the design and development of new technologies for power generation, transportation, defense applications, and industrial heating. In an engineering design cycle, modeling realistic device configurations in a cost- and time-effective manner is required. Due to their flexibility and computational tractability, Reynolds-Averaged Navier-Stokes (RANS)-based models are most commonly used for these purposes. However, these models are known to be inadequate. Turbulent combustion is the coupling of two multiscale, nonlinear phenomena which individually have many modeling challenges. Hence, it is unsurprising that the modeling ansatzes and simplifying assumptions which lead to these practical RANS-based models are suspect. Since RANS-based models will continue to be the dominant tool for turbulent combustion simulation, it is necessary to improve their predictivity through a better understanding of their deficiencies. The are three main modeling issues for turbulent combustion: modeling the turbulent flow, representing the chemical reactions, and capturing the interaction between the turbulence and the chemistry. Model errors can easily be conflated when attempting to quantify deficiencies in this multiphysics context where many individual models are coupled. This work introduces a new technique for isolating these errors through the creation of a flamelet-based direct numerical simulation (DNS) of a nonpremixed, temporally-evolving, planar, reacting jet. DNS is a technique which resolves all lengthscales and timescales of the turbulent flow, providing high-quality data for model development but at a significant computational cost. In the turbulent combustion context, the turbulence-chemistry interaction is also fully resolved. By closing the DNS with a steady laminar flamelet representation, a typical chemical reactions model for RANS-based simulations, RANS turbulence closures and turbulence-chemistry interaction models can be evaluated in isolation through a priori testing. Conversely, by comparing the flamelet DNS to a second DNS employing a higher-fidelity chemistry model, the flamelet closure and its impact on the flame's evolution can be interrogated directly. To obtain the DNS data, a novel algorithm for solving the variable-density, low-Mach Navier-Stokes equations extending the method of Kim, Moin, and Moser for incompressible flow is detailed here. It is a pseudospectral Fourier/B-spline collocation approach which obtains second order accuracy in time and numerical stability for large density ratios with an efficient, matrix-free, iterative treatment of the scalar equations. The a posteriori comparisons of the flamelet DNS and the complex chemistry DNS suggest the flamelet model can significantly alter the evolution of the mean state of the reacting jet; however, violations of global conservation were identified in the complex chemistry DNS. Therefore, no strong conclusions can be made about the chemical reactions model from the comparisons. Significant shortcomings have been identified in the a priori evaluations of the aforementioned RANS closures for turbulent transport, scalar mixing, and turbulence-chemistry interaction, where the flamelet model is taken to be exact. Finally, a flawed assumption in the steady laminar flamelet approach has been directly linked to nonphysical behavior of the density for small values of the scalar dissipation rate

Download or read book Direct Numerical Simulation for Turbulent Reacting Flows written by Thierry Baritaud and published by Editions TECHNIP. This book was released on 1996 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contents: Description of accurate boundary conditions for the simulation of reactive flows. Parallel direct numerical simulation of turbulent reactive flow. Flame-wall interaction and heat flux modelling in turbulent channel flow. A numerical study of laminar flame wall interaction with detailed chemistry: wall temperature effects. Modeling and simulation of turbulent flame kernel evolution. Experimental and theoretical analysis of flame surface density modelling for premixed turbulent combustion. Gradient and counter-gradient transport in turbulent premixed flames. Direct numerical simulation of turbulent flames with complex chemical kinetics. Effects of curvature and unsteadiness in diffusion flames. Implications for turbulent diffusion combustion. Numerical simulations of autoignition in turbulent mixing flows. Stabilization processes of diffusion flames. References.

Download or read book Numerical Approaches to Combustion Modeling written by Elaine S. Oran and published by AIAA (American Institute of Aeronautics & Astronautics). This book was released on 1991 with total page 886 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Analysis of Turbulent Reacting Flows in Complex Combustion Systems written by Murat Yaldizli and published by . This book was released on 2009 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluation of Mixing and Reaction Models for Large eddy Simulation of Nonpremixed Combustion Using Direct Numerical Simulation written by James Clayton Sutherland and published by . This book was released on 2004 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book MILD Combustion Modelling Challenges Experimental Configurations and Diagnostic Tools written by Alessandro Parente and published by Frontiers Media SA. This book was released on 2021-11-26 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Non premixed Combustion Full Numerical Simulation of a Coflowing Axisymmetric Jet Inviscid and Viscous Stability Analysis written by Stanford University. Thermosciences Division. Thermosciences Division and published by . This book was released on 1989 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Manipulation and Control of Jets in Crossflow written by Ann R. Karagozian and published by Springer. This book was released on 2014-05-04 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamental Non-Reactive Jets in Crossflow and Other Jet Systems; Background on Modeling, Dynamical Systems, and Control; Reactive Jets in Crossflow and Multiphase Jets; Controlled Jets in Crossflow and Control via Jet Systems;

Download or read book Mathematical Modelling and Numerical Simulations of Chemically Reacting Turbulent Jets written by Kian Mehravaran and published by . This book was released on 2005 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct Numerical Simulation of Turbulent H2 02 Combustion Using Reduced Chemistry written by C. J. Montgomery and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulent Premixed Flames written by Nedunchezhian Swaminathan and published by Cambridge University Press. This book was released on 2011-04-25 with total page 447 pages. Available in PDF, EPUB and Kindle. Book excerpt: A work on turbulent premixed combustion is important because of increased concern about the environmental impact of combustion and the search for new combustion concepts and technologies. An improved understanding of lean fuel turbulent premixed flames must play a central role in the fundamental science of these new concepts. Lean premixed flames have the potential to offer ultra-low emission levels, but they are notoriously susceptible to combustion oscillations. Thus, sophisticated control measures are inevitably required. The editors' intent is to set out the modeling aspects in the field of turbulent premixed combustion. Good progress has been made on this topic, and this cohesive volume contains contributions from international experts on various subtopics of the lean premixed flame problem.

Download or read book Data Analysis for Direct Numerical Simulations of Turbulent Combustion written by Heinz Pitsch and published by Springer Nature. This book was released on 2020-05-28 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents methodologies for analysing large data sets produced by the direct numerical simulation (DNS) of turbulence and combustion. It describes the development of models that can be used to analyse large eddy simulations, and highlights both the most common techniques and newly emerging ones. The chapters, written by internationally respected experts, invite readers to consider DNS of turbulence and combustion from a formal, data-driven standpoint, rather than one led by experience and intuition. This perspective allows readers to recognise the shortcomings of existing models, with the ultimate goal of quantifying and reducing model-based uncertainty. In addition, recent advances in machine learning and statistical inferences offer new insights on the interpretation of DNS data. The book will especially benefit graduate-level students and researchers in mechanical and aerospace engineering, e.g. those with an interest in general fluid mechanics, applied mathematics, and the environmental and atmospheric sciences.

Download or read book Quality and Reliability of Large Eddy Simulations II written by Maria Vittoria Salvetti and published by Springer Science & Business Media. This book was released on 2010-11-03 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second Workshop on "Quality and Reliability of Large-Eddy Simulations", QLES2009, was held at the University of Pisa from September 9 to September 11, 2009. Its predecessor, QLES2007, was organized in 2007 in Leuven (Belgium). The focus of QLES2009 was on issues related to predicting, assessing and assuring the quality of LES. The main goal of QLES2009 was to enhance the knowledge on error sources and on their interaction in LES and to devise criteria for the prediction and optimization of simulation quality, by bringing together mathematicians, physicists and engineers and providing a platform specifically addressing these aspects for LES. Contributions were made by leading experts in the field. The present book contains the written contributions to QLES2009 and is divided into three parts, which reflect the main topics addressed at the workshop: (i) SGS modeling and discretization errors; (ii) Assessment and reduction of computational errors; (iii) Mathematical analysis and foundation for SGS modeling.

Download or read book A Multi regime Combustion Model for Reactive Flow in Internal Combustion Engines written by Varun Mittal and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: With the ever-rising need for better fuel efficiency and lower emissions, the development of better engine technologies is essential. Developing these technologies requires a good understanding of the interaction between the various coupled multi-physics phenomena present in the engine. Detailed simulations of the engine can potentially provide this. Such simulations are becoming tractable now with the increase in available computational power. Since the combustion process is the primary controlling feature in these engines, an accurate combustion model is essential for enabling these simulations. This model must be efficient and valid across different combustion regimes, since modern engines might operate in hybrid modes. In this work, a framework for studying combustion in engines is developed. In the first part of this work, the focus is on the premixed regime which is dominant in Spark Ignited (SI) engines. The canonical flamelet model used extensively to study constant pressure premixed combustion is extended to variable pressure conditions that are observed in an engine cylinder. An extrapolation procedure is also developed for ensuring a consistent enthalpy and temperature under strong compression. This model is validated against direct numerical simulations with detailed chemistry under different turbulence conditions. The performance of the isobaric model is also evaluated in high turbulence conditions by comparing against detailed experiments of a piloted premixed jet burner with finite rate chemistry and different turbulence levels. In the second part of this work, the autoignition regime is studied, which is the dominant regime in Homogeneous Charge Compression Ignition (HCCI) engines. The Representative Interactive Flamelet (RIF) combustion model has previously been used to describe ignition, combustion, and pollutant formation in direct-injected Diesel engines. It has also been applied successfully for HCCI type combustion. In this work, the RIF model is validated against direct numerical simulation data to evaluate model performance under mixture stratification in Diesel, HCCI, and hybrid regimes. A wide range of thermal stratification and concurrent stratification cases is considered using the model. Since mixed modes are present in a modern engine, a multi-regime combustion model is required. A model is developed in this work by integrating the models for autoignition and premixed regimes. This model is validated against direct numerical simulations with for cases both regimes are important. Finally, simulations of an actual engine are performed. First, the validity of the flow solution is tested by simulating flow bench configurations with no valve motion or reaction. Next, gas exchange simulations of a motored engine are performed. Last, simulation of mixture formation in an engine is performed.

Download or read book Direct Numerical Simulation of Premixed Turbulent Combustion written by Theodoor Cornelis Treurniet and published by . This book was released on 2002 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book NASA Technical Memorandum written by and published by . This book was released on 1994 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct Numerical Simulation of an Unpremixed Jet Flame written by P. Givi and published by . This book was released on 1986 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct numerical simulations have been used to study the effects of large coherent structures in two-dimensional, unpremixed, chemically reacting mixing layers under both temporally evolving and spatially developing assumptions. In the temporally evolving mixing layer calculations, a temperature dependent chemical reaction was incorporated into a computer code that uses pseudospectral numerical methods. The nonequilibrium effects leading to the local quenching of a diffusion flame were investigated. Results indicate that the primary important parameter to be considered for flame extinction is the local instantaneous scalar dissipation rate conditioned at the scalar stoichiometric value. At locations where this value is increased beyond a critical value, the local temperature decreases and the instantaneous reaction rate drops to zero, leading to local quenching of the flame. Purposes of simulating spatially developing flows, a two-dimensional, hybrid pseudospectral-finite difference code was constructed. The resulting code was tested with simulations of the pretransitional region of laboratory mixing layers. Examination of some of the statistical quantities obtained from the results of these simulations are in qualitative agreement with recent experimental data obtained at the California Institute of Technology and Stanford University. The asymmetric nature of the mixing processes has been numerically simulated.