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Author: Pritheesh Gnanaselvam
Publisher:
ISBN:
Category : Computational fluid dynamics
Languages : en
Pages : 140
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Book Description
The simulations and experiments outlined are designed to explore the effect of existing turbulent dispersion models in predicting particle deposition characteristics at higher temperatures. The continuous phase solution was obtained from using a Reynolds-Averaged Navier Stokes (RANS) turbulence model and the turbulent dispersion was modeled using a Continuous Random Walk (CRW) model. Euler-Maruyama scheme was implemented to solve the non-dimensional Langevin equation to model the stochastic nature of the equation appropriately. Previous studies have shown that the particle deposition characteristics depend greatly on the time step of integration. With the Euler-Maruyama scheme, the CFD results were shown to be less sensitive to the time step of integration and with decrease in time step more stable results were obtained. Direct comparison with the Discrete Random Walk (DRW) model shows that DRW fails to predict flow fluctuations seen by particles in the diffusion-impaction regime. Previous studies of this phenomenon were all performed at ambient conditions. The CRW model was shown to predict impact velocities reasonably well, when the chosen time step of integrations is such that the stochastic and damping term are comparable in magnitude. Presented here are pipe-flow experiments conducted in the High Temperature Deposition Facility (HTDF) with a mean jet velocity of 150 m/s – 200 m/s with exit centerline temperature of 1525K to assess the capability of CRW in predicting particle deposition characteristics at high temperatures. The flow temperature was chosen in such a way that the temperature inside the pipe at any point is higher than the melting point of dust used, so that an `all stick’ condition can be used to model particle-wall interactions. The derivation and the effect of the drift correction and the stochastic terms in the normalized Langevin equation were discussed in detail. Simulations were performed trying to reproduce experimental results with and without injection line. The CFD model without injection line was shown to follow the predicted pipe deposition based on the effective drift correction, whereas the CFD model with injection line did not show significant change in pipe deposition results with velocity. CFD results using the OSU-CRW model posited that the model is more appropriate for turbulent pipe flows in the fully developed region.
Author: Pritheesh Gnanaselvam
Publisher:
ISBN:
Category : Computational fluid dynamics
Languages : en
Pages : 140
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Book Description
The simulations and experiments outlined are designed to explore the effect of existing turbulent dispersion models in predicting particle deposition characteristics at higher temperatures. The continuous phase solution was obtained from using a Reynolds-Averaged Navier Stokes (RANS) turbulence model and the turbulent dispersion was modeled using a Continuous Random Walk (CRW) model. Euler-Maruyama scheme was implemented to solve the non-dimensional Langevin equation to model the stochastic nature of the equation appropriately. Previous studies have shown that the particle deposition characteristics depend greatly on the time step of integration. With the Euler-Maruyama scheme, the CFD results were shown to be less sensitive to the time step of integration and with decrease in time step more stable results were obtained. Direct comparison with the Discrete Random Walk (DRW) model shows that DRW fails to predict flow fluctuations seen by particles in the diffusion-impaction regime. Previous studies of this phenomenon were all performed at ambient conditions. The CRW model was shown to predict impact velocities reasonably well, when the chosen time step of integrations is such that the stochastic and damping term are comparable in magnitude. Presented here are pipe-flow experiments conducted in the High Temperature Deposition Facility (HTDF) with a mean jet velocity of 150 m/s – 200 m/s with exit centerline temperature of 1525K to assess the capability of CRW in predicting particle deposition characteristics at high temperatures. The flow temperature was chosen in such a way that the temperature inside the pipe at any point is higher than the melting point of dust used, so that an `all stick’ condition can be used to model particle-wall interactions. The derivation and the effect of the drift correction and the stochastic terms in the normalized Langevin equation were discussed in detail. Simulations were performed trying to reproduce experimental results with and without injection line. The CFD model without injection line was shown to follow the predicted pipe deposition based on the effective drift correction, whereas the CFD model with injection line did not show significant change in pipe deposition results with velocity. CFD results using the OSU-CRW model posited that the model is more appropriate for turbulent pipe flows in the fully developed region.
Author: Timothy Akingbola Ilori
Publisher:
ISBN:
Category :
Languages : en
Pages : 256
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Book Description
Author: Md Alamgir Hossain
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659174643
Category :
Languages : de
Pages : 0
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Book Description
Two separate studies: a comprehensive 3D CFD investigation for multiparticles in turbulence flow and an extended analytical model for liquid-solid phase are presented in this book. CFD investigation was carried out to predict the hydrodynamic behavior of turbid particle flowing through a horizontal pipe networks including loop consist of bends and straight pipes. Furthermore, the extended analytical model was also re-developed for the liquid-solid system to look at the similar behavior of the solid particles flowing in a turbulent field. These two parallel studies will provide better understandings about the turbidity spikes movements in the drinking water distribution networks. This book is design for the lay reader to advance researcher. Lay readers will get information about CFD modelling and particle modelling technique and the researcher will be benefited in turbulent diffusion modelling and multiphase-multiparticle modelling.
Author: Thomas Larry Montgomery
Publisher:
ISBN:
Category :
Languages : en
Pages : 380
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Author: F.C.G.A. Nicolleau
Publisher: Springer
ISBN: 9789400736948
Category : Technology & Engineering
Languages : en
Pages : 154
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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: Yingjie Tang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
In this work, various aerosol particle transport and deposition mechanisms were studied through the computational fluid dynamics (CFD) modeling, including inertial impaction, gravitational effect, lift force, interception, and turbophoresis, within different practical applications including aerosol sampling inlet, filtration system and turbulent pipe flows. The objective of the research is to obtain a better understanding of the mechanisms that affect aerosol particle transport and deposition, and to determine the feasibility and accuracy of using commercial CFD tools in predicting performance of aerosol sampling devices. Flow field simulation was carried out first, and then followed by Lagrangian particle tracking to obtain the aerosol transport and deposition information. The CFD-based results were validated with experimental data and empirical correlations. In the simulation of the aerosol inlet, CFD-based penetration was in excellent agreement with experimental results, and the most significant regional particle deposition occurred due to inertial separation. At higher free wind speeds gravity had less effect on particle deposition. An empirical equation for efficiency prediction was developed considering inertial and gravitational effects, which will be useful for directing design of similar aerosol inlets. In the simulation of aerosol deposition on a screen, a "virtual surface" approach, which eliminates the need for the often-ambiguous user defined functions, was developed to account for particle deposition due to interception. The CFD-based results had a good agreement compared with experimental results, and also with published empirical correlations for interception. In the simulation of turbulent deposition in pipe flows, the relation between particle deposition velocity and wall-normal turbulent velocity fluctuation was quantitative determined for the first time, which could be used to quantify turbulent deposition, without having to carry out Lagrangian particle tracking. It suggested that the Reynolds stress model and large eddy simulation would lead to the most accurate simulated aerosol deposition velocity. The prerequisites were that the wall-adjacent y+ value was sufficiently low, and that sufficient number of prism layers was applied in the near-wall region. The "velocity fluctuation convergence" would be useful criterion for judging the adequacy of a CFD simulation for turbulent deposition.
Author:
Publisher:
ISBN:
Category : Air
Languages : en
Pages : 662
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Author: William Dwight Gerstler
Publisher:
ISBN:
Category :
Languages : en
Pages : 690
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Author: Efstathios Michaelides
Publisher: CRC Press
ISBN: 1315354624
Category : Science
Languages : en
Pages : 1559
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Book Description
The Multiphase Flow Handbook, Second Edition is a thoroughly updated and reorganized revision of the late Clayton Crowe’s work, and provides a detailed look at the basic concepts and the wide range of applications in this important area of thermal/fluids engineering. Revised by the new editors, Efstathios E. (Stathis) Michaelides and John D. Schwarzkopf, the new Second Edition begins with two chapters covering fundamental concepts and methods that pertain to all the types and applications of multiphase flow. The remaining chapters cover the applications and engineering systems that are relevant to all the types of multiphase flow and heat transfer. The twenty-one chapters and several sections of the book include the basic science as well as the contemporary engineering and technological applications of multiphase flow in a comprehensive way that is easy to follow and be understood. The editors created a common set of nomenclature that is used throughout the book, allowing readers to easily compare fundamental theory with currently developing concepts and applications. With contributed chapters from sixty-two leading experts around the world, the Multiphase Flow Handbook, Second Edition is an essential reference for all researchers, academics and engineers working with complex thermal and fluid systems.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 702
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