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Author: Ying Xu Publisher: ISBN: Category : Languages : en Pages : 134
Book Description
Many particle-laden flows in engineering applications involve turbulent gas flows. Modeling multiphase turbulent flows is an important research topic with applications in fluidized beds and particle conveying. A predictive multiphase turbulence model can help CFD codes to be more useful for engineering applications, such as the scale-up in the design of circulating fluidized combustor and coal gasifications. It is reasonable to expect that multiphase turbulence models should at least satisfy some basic modeling and performance criteria and give reasonable predictions for the canonical problems in dilute particle-laden turbulent flows. In this research, a comparative assessment of predictions from Simonin and Ahmadi's turbulence models is performed with direct numerical simulation (DNS) for two canonical problems in particle-laden turbulent flows. Based on the comparative assessment, some criteria and the areas for model improvement are identified: (i) model for interphase TKE transfer, especially the time scale of interphase TKE transfer, and (ii) correct prediction of TKE evolution with variation of particle Stokes number. Some deficiencies that are identified in the Simonin and Ahmadi models limit the applicability. A new multiphase turbulence model, the Equilibration of Energy Model (EEM), is proposed in this work. In EEM, a multiscale interaction time scale is proposed to account for the interaction of a particle with a range of eddy sizes. EEM shows good agreement with the DNS results for particle-laden istropic turbulence. For particle-laden homogeneous shear flows, model predictions from EEM can be further improved if the dissipation rate in fluid phase is modeled with more accuracy. This new time scale is incorporated in the interphase TKE transfer terms of the Simonin and Ahmadi models. For canonical problems in particle-laden turbulent flows, this time scale improves the predictions from these two models. Although EEM is a simple model, it has a clear physical interpretation and gives reasonable predictions for two canonical problems in particle-laden turbulent flows. It can be a useful engineering tool for CFD calculations of gas-solid two phase flows.
Author: Ying Xu Publisher: ISBN: Category : Languages : en Pages : 134
Book Description
Many particle-laden flows in engineering applications involve turbulent gas flows. Modeling multiphase turbulent flows is an important research topic with applications in fluidized beds and particle conveying. A predictive multiphase turbulence model can help CFD codes to be more useful for engineering applications, such as the scale-up in the design of circulating fluidized combustor and coal gasifications. It is reasonable to expect that multiphase turbulence models should at least satisfy some basic modeling and performance criteria and give reasonable predictions for the canonical problems in dilute particle-laden turbulent flows. In this research, a comparative assessment of predictions from Simonin and Ahmadi's turbulence models is performed with direct numerical simulation (DNS) for two canonical problems in particle-laden turbulent flows. Based on the comparative assessment, some criteria and the areas for model improvement are identified: (i) model for interphase TKE transfer, especially the time scale of interphase TKE transfer, and (ii) correct prediction of TKE evolution with variation of particle Stokes number. Some deficiencies that are identified in the Simonin and Ahmadi models limit the applicability. A new multiphase turbulence model, the Equilibration of Energy Model (EEM), is proposed in this work. In EEM, a multiscale interaction time scale is proposed to account for the interaction of a particle with a range of eddy sizes. EEM shows good agreement with the DNS results for particle-laden istropic turbulence. For particle-laden homogeneous shear flows, model predictions from EEM can be further improved if the dissipation rate in fluid phase is modeled with more accuracy. This new time scale is incorporated in the interphase TKE transfer terms of the Simonin and Ahmadi models. For canonical problems in particle-laden turbulent flows, this time scale improves the predictions from these two models. Although EEM is a simple model, it has a clear physical interpretation and gives reasonable predictions for two canonical problems in particle-laden turbulent flows. It can be a useful engineering tool for CFD calculations of gas-solid two phase flows.
Author: Publisher: ISBN: Category : Languages : en Pages : 93
Book Description
Many particle-laden flows in engineering applications involve turbulent gas flows. Modeling multiphase turbulent flows is an important research topic with applications in fluidized beds and particle conveying. A predictive multiphase turbulence model can help CFD codes to be more useful for engineering applications, such as the scale-up in the design of circulating fluidized combustor and coal gasifications. In engineering applications, the particle volume fraction can vary from dilute (10sup-4
Author: American Society of Mechanical Engineers. Fluids Engineering Division. Summer Meeting Publisher: ISBN: Category : Fluid dynamics Languages : en Pages : 828
Author: Pierre Sagaut Publisher: World Scientific ISBN: 186094650X Category : Science Languages : en Pages : 356
Book Description
This unique book gives a general unified presentation of the use of the multiscale/multiresolution approaches in the field of turbulence. The coverage ranges from statistical models developed for engineering purposes to multiresolution algorithms for the direct computation of turbulence. It provides the only available up-to-date reviews dealing with the latest and most advanced turbulence models (including LES, VLES, hybrid RANS/LES, DES) and numerical strategies.The book aims at providing the reader with a comprehensive description of modern strategies for turbulent flow simulation, ranging from turbulence modeling to the most advanced multilevel numerical methods.
Author: Lixing Zhou Publisher: Butterworth-Heinemann ISBN: 0128134666 Category : Technology & Engineering Languages : en Pages : 343
Book Description
Theory and Modeling of Dispersed Multiphase Turbulent Reacting Flows gives a systematic account of the fundamentals of multiphase flows, turbulent flows and combustion theory. It presents the latest advances of models and theories in the field of dispersed multiphase turbulent reacting flow, covering basic equations of multiphase turbulent reacting flows, modeling of turbulent flows, modeling of multiphase turbulent flows, modeling of turbulent combusting flows, and numerical methods for simulation of multiphase turbulent reacting flows, etc. The book is ideal for graduated students, researchers and engineers in many disciplines in power and mechanical engineering. Provides a combination of multiphase fluid dynamics, turbulence theory and combustion theory Covers physical phenomena, numerical modeling theory and methods, and their applications Presents applications in a wide range of engineering facilities, such as utility and industrial furnaces, gas-turbine and rocket engines, internal combustion engines, chemical reactors, and cyclone separators, etc.
Author: F.C.G.A. Nicolleau Publisher: Springer Science & Business Media ISBN: 940072506X Category : Technology & Engineering Languages : en Pages : 159
Book Description
This book contains a collection of the main contributions from the first five workshops held by Ercoftac Special Interest Group on Synthetic Turbulence Models (SIG42. It is intended as an illustration of the sig’s activities and of the latest developments in the field. This volume investigates the use of Kinematic Simulation (KS) and other synthetic turbulence models for the particular application to environmental flows. This volume offers the best syntheses on the research status in KS, which is widely used in various domains, including Lagrangian aspects in turbulence mixing/stirring, particle dispersion/clustering, and last but not least, aeroacoustics. Flow realizations with complete spatial, and sometime spatio-temporal, dependency, are generated via superposition of random modes (mostly spatial, and sometime spatial and temporal, Fourier modes), with prescribed constraints such as: strict incompressibility (divergence-free velocity field at each point), high Reynolds energy spectrum. Recent improvements consisted in incorporating linear dynamics, for instance in rotating and/or stably-stratified flows, with possible easy generalization to MHD flows, and perhaps to plasmas. KS for channel flows have also been validated. However, the absence of "sweeping effects" in present conventional KS versions is identified as a major drawback in very different applications: inertial particle clustering as well as in aeroacoustics. Nevertheless, this issue was addressed in some reference papers, and merits to be revisited in the light of new studies in progress.
Author: Cheng Chen Publisher: Springer ISBN: 3662483734 Category : Science Languages : en Pages : 131
Book Description
This book explores the Energy Minimization Multi-scale (EMMS) theory and the drag model for heterogeneous gas-solid fluidized flows. The results show that the cluster density plays a critical role with regard to drag. A novel cluster model is proposed and indicates that the profile of cluster density is single-peaked with the maximum value located at solid concentrations of 0.1~0.15. The EMMS theory is improved with the cluster model and an accurate drag model is developed. The model’s universality is achieved by investigating the relationship between the heterogeneity and flow patterns. The drag model is subsequently verified numerically and experimentally.
Author: David Schellander Publisher: GRIN Verlag ISBN: 3656501920 Category : Technology & Engineering Languages : en Pages : 155
Book Description
Doctoral Thesis / Dissertation from the year 2013 in the subject Engineering - Mechanical Engineering, grade: 1, University of Linz (Department on Particulate Flow Modelling), language: English, abstract: The numerical hybrid model EUgran+, which is an Eulerian-Eulerian granular phase model extended with models from the Eulerian-Lagrangian model for dense rapid particulate flows, is modified to account for poly-dispersed particle diameter distributions. These modifications include the implementation of I) a new poly-dispersed drag law and of II) new particle boundary conditions distinguishing between sliding and non-sliding particle-wall collisions and III) a new implementation of the population balance equation in the agglomeration model using the Eulerian-Lagrangian approach, referred to as Bus-stop model. Further, the applicability of the EUgran+ model is extended to cover dilute to dense poly-disperse particulate flows. Furthermore, this provides an improvement in the numerical simulation of dust separation and the formation of particle strands in industrial scale cyclones. In this PHD thesis, the EUgran+Poly model is validated at 3 specific cases with different mass loadings: I) poly-dispersed particle conveying in a square pipe with a 90 degree bend at low mass loading (L = 0:00206); II) a particle conveying case in a rectangular pipe with a double-loop at high mass loading (L = 1:5); III) in a vertical pipe the implementation of the agglomeration model is validated. To show the applicability of the presented models a simulation of an industrial cyclone in experimental scale is presented. The validation and application shows that considering a poly-disperse Eulerian-Eulerian granular phase improves the accordance of the simulation results with measurements significantly. Finally, the hybrid model is a good compromise for a computational efficient simulation of particulate transport and separation with different mass loading regimes.
Author: Ying Xu
Author: Ying Xu
Author: 
Author: American Society of Mechanical Engineers. Fluids Engineering Division. Summer Meeting
Author: 
Author: Iowa State University
Author: Pierre Sagaut
Author: Lixing Zhou
Author: F.C.G.A. Nicolleau
Author: Cheng Chen
Author: David Schellander