This research paper deals with the fusion of non-Newtonian fluid dynamics and turbulence theories in paper making flows and applies them to highly non-Newtonian materials, viz., wood fiber and paper pulp suspensions, in turbulent flows. The materials were characterized by using the continuum approach, and their flow was expected to obey the conservation laws of continuum mechanics. The study aimed to examine the possibiliite of using non-Newtonian fluid models for simulation of turbulent flow. Rheological measurements were made to determine the shear viscosity of suspensions, and the results of other studies were analyzed. The studied materials were shear thinning at moderate shear rates, and at small deformations pulp suspensions exhibited some viscoelastic and yield stress behavior. At high shear rates and in a tuirbulent flow field, fiber suspensions had a marked effect on the turbulent qualities examined. Furthermore, measurements were run to determine the thermodynamical state inside the refiner and its effect on the quality of the pulp produced. (...).

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.

Modelling Approaches and Computational Methods for Particle-laden Turbulent Flows introduces the principal phenomena observed in applications where turbulence in particle-laden flow is encountered while also analyzing the main methods for analyzing numerically. The book takes a practical approach, providing advice on how to select and apply the correct model or tool by drawing on the latest research. Sections provide scales of particle-laden turbulence and the principal analytical frameworks and computational approaches used to simulate particles in turbulent flow. Each chapter opens with a section on fundamental concepts and theory before describing the applications of the modelling approach or numerical method. Featuring explanations of key concepts, definitions, and fundamental physics and equations, as well as recent research advances and detailed simulation methods, this book is the ideal starting point for students new to this subject, as well as an essential reference for experienced researchers. - Provides a comprehensive introduction to the phenomena of particle laden turbulent flow - Explains a wide range of numerical methods, including Eulerian-Eulerian, Eulerian-Lagrange, and volume-filtered computation - Describes a wide range of innovative applications of these models

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.

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.

This book presents recent progress in the application of RANS turbulence models based on the Reynolds stress transport equations. A variety of models has been implemented by different groups into different flow solvers and applied to external as well as to turbo machinery flows. Comparisons between the models allow an assessment of their performance in different flow conditions. The results demonstrate the general applicability of differential Reynolds stress models to separating flows in industrial aerodynamics.