Download or read book Eddy Dissipation Model for Modeling of Turbulent Non premixed Combustion with Radiation Effect Using Openfoam written by Hassan Ibrahim Hassan Mohamed Kassem and published by . This book was released on 2011 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Eddy Dissipation Modeling of Turbulent Non premixed Combustion with Radiation Effect Using Openfoam written by Hassan Ibrahim Hassan Mohamed Kassem and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Framework for Turbulent Non premixed Combustion Modeling in OpenFoam written by Vasu Jaganath and published by . This book was released on 2020 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustion remains a critical technology for electricity generation, heating, transportation and other industrial processes. Turbulent combustion lies at the heart of many of these processes. The accurate, robust and efficient computational modeling of turbulent combustion is necessary to design clean, efficient and safe combustion devices and processes. For practical combustion problems the direct numerical simulation (DNS) of the governing equations is computationally intractable. The Reynolds averaged Navier-Stokes simulation (RANS) and large eddy simulation (LES) techniques have emerged as powerful tools to simulate turbulent reacting flows. RANS and LES methodologies require closure of the unclosed terms arising from the averaging or filtering the governing equations. Even with adequate closure, RANS and LES remain computationally infeasible for simulating many combustion processes in engineering applications, further simplifications regarding flame thickness, flow and chemical reaction time scales are required. The high Damk\"{o}hler (Da) number flames can be modeled using a reduced chemistry model. A flamelet derived reduced chemistry model like Flamelet Generated Manifolds (FGM) accounts for finite rate chemistry while it greatly simplifies the simulation of turbulent combustion as it decouples the turbulent transport and flame structure. The interaction between the turbulence and the flame front in non-premixed combustion is described by the probability density function (PDF) of the composition variables. In this work, a framework for turbulent combustion modeling is presented for both RANS and, LES with FGM reduced chemistry model. This framework consists of implementation of presumed and transported PDF models and is developed within the open source CFD software OpenFOAM. The simulation of the well-known piloted methane-air jet flames (Sandia flames) is conducted in RANS context with both presumed and transported PDF models. An "A priori" analysis is conducted based on the RANS/TPDF simulation data. The analysis quantifies the extent of errors in PPDF models, specifically errors in choice of presumed PDF, statistical independence and the number moments and cross moments considered. A new PPDF model based on the Gaussian copula approach for correlation of the composition variables is developed and analyzed. The implementation of RANS/TPDF solver incorporates robust algorithms for particle tracking, position and number control. The LES/TFDF simulation of Sandia flame D is conducted to showcase the capability of the developed framework.
Download or read book Turbulent Combustion written by Norbert Peters and published by Cambridge University Press. This book was released on 2000-08-15 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: The combustion of fossil fuels remains a key technology for the foreseeable future. It is therefore important that we understand the mechanisms of combustion and, in particular, the role of turbulence within this process. Combustion always takes place within a turbulent flow field for two reasons: turbulence increases the mixing process and enhances combustion, but at the same time combustion releases heat which generates flow instability through buoyancy, thus enhancing the transition to turbulence. The four chapters of this book present a thorough introduction to the field of turbulent combustion. After an overview of modeling approaches, the three remaining chapters consider the three distinct cases of premixed, non-premixed, and partially premixed combustion, respectively. This book will be of value to researchers and students of engineering and applied mathematics by demonstrating the current theories of turbulent combustion within a unified presentation of the field.
Download or read book Conjugate Problems in Convective Heat Transfer written by Abram S. Dorfman and published by CRC Press. This book was released on 2009-08-26 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Illustrates Calculations Using Machine and Technological Processes The conjugate heat transfer (CHT) problem addresses the thermal interaction between a body and fluid flowing over or through it. This is an essential consideration in nature and different areas of engineering, including mechanics, aerospace, nuclear engineering, biology, and meteorology. Advanced conjugate modeling of the heat transfer process is now used extensively in a wide range of applications. Conjugate Problems in Convective Heat Transfer addresses the latest theory, methods, and applications associated with both analytical and numerical methods of solution CHT problems and their exact and approximate solutions. It demonstrates how the true value of a CHT solution is derived by applying these solutions to contemporary engineering design analysis. Assembling cutting-edge information on modern modeling from more than 200 publications, this book presents more than 100 example applications in thermal treatment materials, machinery operation, and technological processes. Creating a practical review of current CHT development, the author includes methods associated with estimating heat transfer, particularly that from arbitrary non-isothermal surfaces in both laminar and turbulent flows. Harnesses the Modeling Power of CHT Unique in its consistent compilation and application of current knowledge, this book presents advanced CHT analysis as a powerful tool for modeling various device operations and technological processes, from relatively simple procedures to complex multistage, nonlinear processes.
Download or read book Large Eddy Simulation of a Fuel rich Turbulent Non premixed Reacting Flow with Radiative Heat Transfer written by Sreebash Chandra Paul and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The aims of this thesis are to apply the Large Eddy Simulation (LES) and beta Probability Density Function ([beta]-PDF) for the simulation of turbulent non-premixed reacting flow, in particularly for the predictions of soot and NO production, and to investigate the radiative heat transfer during combustion process applying Discrete Ordinates Method (DOM). LES seeks the solution by separating the flow field into large-scale eddies, which carry the majority of the energy and are resolved directly, and small-scale eddies, which have been modelled via Smagorinsky model with constant Cs (Smagorinsky model constant) as well as its dynamic calibration. This separation has been made by applying a filtering approach to the governing equations describing the turbulent reacting flow. Firstly, LES technique is applied to investigate the turbulent flow, temperature and species concentrations during the combustion process within an axi-symmetric model cylindrical combustion chamber.
Download or read book Theoretical and Numerical Combustion written by Thierry Poinsot and published by R.T. Edwards, Inc.. This book was released on 2005 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introducing numerical techniques for combustion, this textbook describes both laminar and turbulent flames, addresses the problem of flame-wall interaction, and presents a series of theoretical tools used to study the coupling phenomena between combustion and acoustics. The second edition incorporates recent advances in unsteady simulation methods,
Download or read book Turbulent Combustion Modeling written by Tarek Echekki and published by Springer Science & Business Media. This book was released on 2010-12-25 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent combustion sits at the interface of two important nonlinear, multiscale phenomena: chemistry and turbulence. Its study is extremely timely in view of the need to develop new combustion technologies in order to address challenges associated with climate change, energy source uncertainty, and air pollution. Despite the fact that modeling of turbulent combustion is a subject that has been researched for a number of years, its complexity implies that key issues are still eluding, and a theoretical description that is accurate enough to make turbulent combustion models rigorous and quantitative for industrial use is still lacking. In this book, prominent experts review most of the available approaches in modeling turbulent combustion, with particular focus on the exploding increase in computational resources that has allowed the simulation of increasingly detailed phenomena. The relevant algorithms are presented, the theoretical methods are explained, and various application examples are given. The book is intended for a relatively broad audience, including seasoned researchers and graduate students in engineering, applied mathematics and computational science, engine designers and computational fluid dynamics (CFD) practitioners, scientists at funding agencies, and anyone wishing to understand the state-of-the-art and the future directions of this scientifically challenging and practically important field.
Download or read book Direct and Large Eddy Simulation XI written by Maria Vittoria Salvetti and published by Springer. This book was released on 2019-02-02 with total page 562 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the proceedings of the 11th workshop on Direct and Large Eddy Simulation (DLES), which was held in Pisa, Italy in May 2017. The event focused on modern techniques for simulating turbulent flows based on the partial or full resolution of the instantaneous turbulent flow structures, as Direct Numerical Simulation (DNS), Large-Eddy Simulation (LES) or hybrid models based on a combination of LES and RANS approaches. In light of the growing capacities of modern computers, these approaches have been gaining more and more interest over the years and will undoubtedly be developed and applied further. The workshop offered a unique opportunity to establish a state-of-the-art of DNS, LES and related techniques for the computation and modeling of turbulent and transitional flows and to discuss about recent advances and applications. This volume contains most of the contributed papers, which were submitted and further reviewed for publication. They cover advances in computational techniques, SGS modeling, boundary conditions, post-processing and data analysis, and applications in several fields, namely multiphase and reactive flows, convection and heat transfer, compressible flows, aerodynamics of airfoils and wings, bluff-body and separated flows, internal flows and wall turbulence and other complex flows.
Download or read book Large Eddy Simulations of Turbulent Combustion Including Radiative Heat Transfer written by Rogério Goncalves Dos santos and published by . This book was released on 2008 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: The combustion is one of the principal ways to produced energy used nowadays, it is also a complex phenomenon, where the turbulent flow, chemical reactions, different phases and different heat transfer phenomena can interact. Better understanding of these interactions is essential to improve the actual combustion system and to developed the new ones. The goal of this thesis is to study the interaction of the turbulent combustion with the thermal radiation by the use of three-dimensional numerical simulation. For that, using a computational tool named CORBA, a code for the combustion Large Eddy Simulation (LES) was coupled with a radiative heat transfer code. This technique allows the exchange of information between the two codes without big changes in their structure, then it is possible to take advantages of the different characteristic time from each phenomenon in a high performance parallel computational environment. In a first time, two-dimensional simulation of a turbulent propane/air premixed flame stabilized downstream a triangular flame holder has been realised. After the changing of the twodimensional radiation code for another three-dimensional one, the same configuration was simulated in 3D. A mesh with more than 4.7 millions cells for the combustion code (AVBP) and more than 3.3 millions cells for the radiation code (DOMASIUM) are used. Results show a changing in the temperature and species fields, as well as in the flame dynamics when the thermal radiation was taken into account, with a minor intensity in the three-dimensional simulations. This method, also, shows that it is possible to perform 3D complex simulations in a industrial acceptable time.
Download or read book Chemical Modeling for Large Eddy Simulation of Turbulent Combustion written by and published by . This book was released on 2009 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the present project the focus was on developing advanced combustion models for large-eddy simulations (LES) and to develop automatic chemistry reduction techniques and reduced chemical mechanisms for JP-8 surrogate fuels. The aim of the combustion LES modeling part was to advance the models for non-premixed and premixed combustion towards a generalized combustion model that covers all combustion regimes. Towards this end, for the premixed regime, a dynamic model for the turbulent burning velocity was developed, which eliminates adjustable coefficients from the premixed combustion model, and a flame structure model was presented, which considers local broadening of the flame preheat zone. Further, based on asymptotic arguments, a formalism to identify the correct combustion regime was developed, which will be an important element in a future generalized combustion-regime independent combustion model. In the second part of the project, several advancements led to a fully automatic chemistry reduction method. New developments include a refined DRGEP method for species and reaction elimination, a chemical lumping procedure, and an automatic procedure for selecting steady state species. Further, several potential surrogate fuel components have been included in the component library, and a reduced JP-8 surrogate mechanism was constructed and tested with experimental data.
Download or read book Radiative Heat Transfer in Turbulent Combustion Systems written by Michael F. Modest and published by Springer. This book was released on 2016-01-06 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: This introduction reviews why combustion and radiation are important, as well as the technical challenges posed by radiation. Emphasis is on interactions among turbulence, chemistry and radiation (turbulence-chemistry-radiation interactions – TCRI) in Reynolds-averaged and large-eddy simulations. Subsequent chapters cover: chemically reacting turbulent flows; radiation properties, Reynolds transport equation (RTE) solution methods, and TCRI; radiation effects in laminar flames; TCRI in turbulent flames; and high-pressure combustion systems. This Brief presents integrated approach that includes radiation at the outset, rather than as an afterthought. It stands as the most recent developments in physical modeling, numerical algorithms, and applications collected in one monograph.
Download or read book Modeling of Turbulent Mixing in Combustion LES written by Abhishek Jain and published by . This book was released on 2017 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current work focusses on investigating previously formulated subfilter mixing models for scalar variance and dissipation prediction in large eddy simulation (LES) of turbulent reacting flows. Three different models based on the local equilibrium assumption (Pierce, C. D., & Moin, P. Physics of Fluids (10), 3041, 1998), the second-moment transport equation (STE), and the variance transport equation (VTE) (Kaul, C. M. et al. Proceedings of the Combustion Institute (34), 1289-1297, 2013) are assessed. The emphasis of the investigation is placed on the effects of the discretization errors on the prediction of sub-filter variance and scalar dissipation rates. Estimation of subfilter quantities is a crucial procedure for LES. Among other subfilter quantities, the subfilter variance of the mixture fraction is particularly important for LES of non-premixed combustion because of the role it plays in the prediction of mixing of the fuel and co-flow at the molecular level. Previous works have assumed an equilibrium between the production and dissipation of the variance at these subfilter scales, and models based on this assumption have been developed with dynamic estimation of a model constant. Recent works have focused on eliminating this assumption of local equilibrium of production and dissipation of variance. Two of these approaches were studied and implemented for a non-premixed flame and their results are compared. In the first approach, the subfilter variance was calculated by solving the transport equation for the second moment of the mixture fraction (STE). The second approach solved the transport equation for the subfilter scalar variance itself (VTE). Both models incorporate the same modeled quantity for the scalar dissipation rate. It is seen from the results that the STE approach substantially overpredicts the subfilter variance. This discrepancy is attributed to the error generated due to the discrete version of the product rule for differentiation that is used when deriving the equation for the subfilter variance from the second and first moment transport equation for the mixture fraction. This error acts as an artificial source term and results in the overprediction of the subfilter variance in the STE approach. The contribution of this artificial source term is found to be much larger than that of the actual production term. Due to this susceptible nature of the STE approach to numerical errors, it is suggested to calculate the subfilter variance by solving a transport equation for it, i.e., the VTE approach. A dynamic approach for the model coefficient of the subfilter scalar dissipation in the VTE approach is also implemented. This model is used to simulate the Sandia Flame D with a 1-D Conditional Moment Closure (CMC) combustion model. The results show satisfactory agreement with experimental data.
Download or read book Numerical Simulation of Non premixed Turbulent Combustion written by Stephen M. De Bruyn Kops and published by . This book was released on 1999 with total page 187 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 Large Eddy Simulation of Non Premixed Turbulent Combustion written by Parviz Moin and published by . This book was released on 1999 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Adaptive and Convergent Methods for Large Eddy Simulation of Turbulent Combustion written by Colin Russell Heye and published by . This book was released on 2014 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the recent past, LES methodology has emerged as a viable tool for modeling turbulent combustion. LES computes the large scale mixing process accurately, thereby providing a better starting point for small-scale models that describe the combustion process. Significant effort has been made over past decades to improve accuracy and applicability of the LES approach to a wide range of flows, though the current conventions often lack consistency to the problems at hand. To this end, the two main objectives of this dissertation are to develop a dynamic transport equation-based combustion model for large- eddy simulation (LES) of turbulent spray combustion and to investigate grid- independent LES modeling for scalar mixing. Long-standing combustion modeling approaches have shown to be suc- cessful for a wide range of gas-phase flames, however, the assumptions required to derive these formulations are invalidated in the presence of liquid fuels and non-negligible evaporation rates. In the first part of this work, a novel ap- proach is developed to account for these evaporation effects and the resulting multi-regime combustion process. First, the mathematical formulation is de- rived and the numerical implementation in a low-Mach number computational solver is verified against one-dimensional and lab scale, both non-reacting and reacting spray-laden flows. In order to clarify the modeling requirements in LES for spray combustion applications, results from a suite of fully-resolved direct numerical simulations (DNS) of a spray laden planar jet flame are fil- tered at a range of length scales. LES results are then validated against two sets of experimental jet flames, one having a pilot and allowing for reduced chemistry modeling and the second requiring the use of detail chemistry with in situ tabulation to reduce the computational cost of the direct integration of a chemical mechanism. The conventional LES governing equations are derived from a low-pass filtering of the Navier-Stokes equations. In practice, the filter used to derive the LES governing equations is not formally defined and instead, it is assumed that the discretization of LES equations will implicitly act as a low-pass filter. The second part of this study investigates an alternative derivation of the LES governing equations that requires the formal definition of the filtering operator, known as explicitly filtered LES. It has been shown that decoupling the filter- ing operation from the underlying grid allows for the isolation of subfilter-scale modeling errors from numerical discretization errors. Specific to combustion modeling are the aggregate errors associated with modeling sub-filter distribu- tions of scalars that are transported by numerical impacted turbulent fields. Quantities of interest to commonly-used combustion models, including sub- filter scalar variance and filtered scalar dissipation rate, are investigated for both homogeneous and shear-driven turbulent mixing.
