Numerical Modeling of Fibre Suspensions in Grid-generated Turbulent Flow PDF Download
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Languages : en
Pages :
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Languages : en
Pages :
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Author: Atanasis Plikas
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ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Cellulose fibre floc formation and destruction by hydrodynamic forces in a grid-generated turbulent flow, such as that occurring downstream of turbulence generators in headboxes, is investigated using computational fluid dynamics (CFD) modeling. A Large Eddy Simulation was performed to elucidate the physics behind the break up of fibre flocs. Upon comparison with experimental data on fibre suspension flows, it was found that the minimum fibre flocculation coincided with the maximum time dependence and strain in the mean motion. The turbulent kinetic energy at these locations was negligible. A numerical model of the fibre flow was developed using an Eulerian multiphase flow model in where a transport equation for flocculation intensity was solved together with the momentum equations and turbulence models. Agreement with experimental data is good far downstream of the grids, but inadequate in the anisotropic flow immediately downstream of the grids.
Author: Oleg Mikhailovich Belotserkovskii
Publisher: World Scientific
ISBN: 9812833021
Category : Science
Languages : en
Pages : 489
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The book provides an original approach in the research of structural analysis of free developed shear compressible turbulence at high Reynolds number on the base of direct numerical simulation (DNS) and instability evolution for ideal medium (integral conservation laws) with approximate mechanism of dissipation (FLUX dissipative monotone OC upwindOCO difference schemes) and does not use any explicit sub-grid approximation and semi-empirical models of turbulence. Convective mixing is considered as a principal part of conservation law.
Author: Tapan K. Sengupta
Publisher: Springer
ISBN: 9811300380
Category : Technology & Engineering
Languages : en
Pages : 393
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Book Description
This book highlights by careful documentation of developments what led to tracking the growth of deterministic disturbances inside the shear layer from receptivity to fully developed turbulent flow stages. Associated theoretical and numerical developments are addressed from basic level so that an uninitiated reader can also follow the materials which lead to the solution of a long-standing problem. Solving Navier-Stokes equation by direct numerical simulation (DNS) from the first principle has been considered as one of the most challenging problems of understanding what causes transition to turbulence. Therefore, this book is a very useful addition to advanced CFD and advanced fluid mechanics courses.
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Category : Aeronautics
Languages : en
Pages : 704
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Author: Fernando F. Grinstein
Publisher: Cambridge University Press
ISBN: 1316571742
Category : Technology & Engineering
Languages : en
Pages : 481
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Small-scale turbulent flow dynamics is traditionally viewed as universal and as enslaved to that of larger scales. In coarse grained simulation (CGS), large energy-containing structures are resolved, smaller structures are spatially filtered out, and unresolved subgrid scale (SGS) effects are modeled. Coarse Grained Simulation and Turbulent Mixing reviews our understanding of CGS. Beginning with an introduction to the fundamental theory the discussion then moves to the crucial challenges of predictability. Next, it addresses verification and validation, the primary means of assessing accuracy and reliability of numerical simulation. The final part reports on the progress made in addressing difficult non-equilibrium applications of timely current interest involving variable density turbulent mixing. The book will be of fundamental interest to graduate students, research scientists, and professionals involved in the design and analysis of complex turbulent flows.
Author: F.C.G.A. Nicolleau
Publisher: Springer Science & Business Media
ISBN: 940072506X
Category : Technology & Engineering
Languages : en
Pages : 159
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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: James W. Daily
Publisher:
ISBN:
Category : Turbulence
Languages : en
Pages : 84
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Book Description
In a previous report techniques were described for measuring turbulence and velocity profiles in turbulent shear flows of water and dilute fiber suspensions, and some preliminary results presented. The present report describes subsequent experience with the techniques, and the results of their application to an extended range of flow velocities and an additional wood pulp suspension. The report has two areas of emphasis. The first has to do with some basic facts about turbulence, together with relevant theoretical relations among variables and their implications as regards problems of measurement and analysis. The second relates to the specific -measurements and their significance as regards flowing fiber suspensions. The results confirm and extend the previous conclusions regarding the .mechanism of turbulence and the momentum transfer process in dilute fiber suspensions. In particular, the significance of the combined roles of turbulence and fiber entanglement in diffusion and mixing is examined in detail. The necessity of isolating these roles is discussed and recommendations presented. The procedures employed for data measurement and analysis of the statistically turbulent flow are: analyzed and recommendations made.
Author:
Publisher:
ISBN:
Category : Mechanics, Applied
Languages : en
Pages : 400
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Author:
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ISBN:
Category : Aeronautics
Languages : en
Pages : 1048
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