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Hyensjö, Marko. "On fibre suspension flow modelling : mechanical fibre flocculation and fibre orientation /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-344.
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Kvick, Mathias. "Transitional and turbulent fibre suspension flows." Doctoral thesis, KTH, Strömningsfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-153018.
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In this thesis the orientation of macro-sized fibres in turbulent flows is studied, as well as the effect of nano-sized fibrils on hydrodynamic stability. The focus lies on enabling processes for new materials where cellulose is the main constituent. When fibres (or any elongated particles) are added to a fluid, the complexity of the flow-problem increases. The fluid flow will influence the rotation of the fibres, and therefore also effect the overall fibre orientation. Exactly how the fibres rotate depends to a large extent on the mean velocity gradient in the flow. In addition, when fibres are added to a suspending fluid, the total stress in the suspension will increase, resulting in an increased apparent viscosity. The increase in stress is related to the direction of deformation in relation to the orientation of the particle, i.e. whether the deformation happens along the long or short axis of the fibre. The increase in stress, which in most cases is not constant neither in time nor space, will in turn influence the flow. This thesis starts off with the orientation and spatial distribution of fibres in the turbulent flow down an inclined plate. By varying fibre and flow parameters it is discovered that the main parameter controlling the orientation distribution is the aspect ratio of the fibres, with only minor influences from the other parameters. Moreover, the fibres are found to agglomerate into streamwise streaks. A new method to quantify this agglomeration is developed, taking care of the problems that arise due to the low concentration in the experiments. It is found that streakiness, i.e. the tendency to agglomerate in streaks, varies with Reynolds number. Going from fibre orientation to flow dynamics of fibre suspensions, the influence of cellulose nanofibrils (CNF) on laminar/turbulent transition is investigated in three different setups, namely plane channel flow, curved-rotating channel flow, and the flow in a flow focusing device. This last flow case is selected since it is can be used for assembly of CNF based materials. In the plane channel flow, the addition of CNF delays the transition more than predicted from measured viscosities while in the curved-rotating channel the opposite effect is discovered. This is qualitatively confirmed by linear stability analyses. Moreover, a transient growth analysis in the plane channel reveals an increase in streamwise wavenumber with increasing concentration of CNF. In the flow focusing device, i.e. at the intersection of three inlets and one outlet, the transition is found to mainly depend on the Reynolds number of the side flow. Recirculation zones forming downstream of two sharp corners are hypothesised to be the cause of the transition. With that in mind, the two corners are given a larger radius in an attempt to stabilise the flow. However, if anything, the flow seems to become unstable at a smaller Reynolds number, indicating that the separation bubble is not the sole cause of the transition. The choice of fluid in the core flow is found to have no effect on the stability, neither when using fluids with different viscosities nor when a non-Newtonian CNF dispersion was used. Thus, Newtonian model fluids can be used when studying the flow dynamics in this type of device. As a proof of concept, a flow focusing device is used to produce a continuous film from CNF. The fibrils are believed to be aligned due to the extensional flow created in the setup, resulting in a transparent film, with an estimated thickness of 1 um.<br><p>QC 20141003</p>
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Yan, Huawei. "Fibre suspension flocculation under simulated forming conditions." Doctoral thesis, KTH, Fibre and Polymer Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3794.
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<p>A flow loop system for study of fibre flocculation insuspensions has been developed. The system is designed tosimulate the flow conditions in a paper machine headbox. It isequipped with a radial distributor feeding a step diffuser pipepackage, after which the flow is contracted in a 2-D nozzle.The flow system is also equipped with a secondary flowcontraction with an area reduction ratio of 2:1 after theheadbox nozzle, mimicking accelerations that may take placeduring forming. The flow system is equipped with heating andcooling devices for the study of temperature effects on fibresuspension flocculation. An online dosage device for the studyof chemical effects on fibre suspension flocculation is alsoincluded. The maximum flow velocity in the system is 16m/s.</p><p>Flowing fibre suspensions were studied using a high speedCCD video camera and transmitted infra-red laser light pulseillumination. Images were taken either separately before andafter or along the secondary contraction. Images of fibreflocculation were evaluated by power spectrum analysis, and themean floc size and the flocculation index were calculated. Aconcept of mean floc area reduction, based on power spectrum,has been introduced to characterise the fibre network insuspensions. By comparingthe fibre flocculation before andafter the secondary contraction, or by following the fibreflocs along the secondary contraction, floc rheologyinformation can be obtained. The effects of chemical additivesand fibre surface modification can also be studied by comparingthe corresponding fibre flocculation.</p><p>For a bleached softwood kraft pulp suspension at a fibreconcentration of 5 g/l, the fibre flocs along the secondarycontraction have been manually evaluated, and the resultsconfirm that the power spectrum analysis is applicable. Ca 1/5of the flocs were broken into two by the contraction. The meanfloc size increases in MD while in CD it decreases during theflow contraction. Both the floc aspect ratio and the flocorientation in MD increase during the flow contraction. The netfibre floc area is decreased and the fibre flocs areconcentrated by the flow contraction, which is confirmed by anincrease of gray value of the flocs in the light transmissionimages. The dewatering of fibre flocs may thus have alreadybeen started in the suspension before reaching the wires in theforming zone.</p><p>Some physical influences on fibre suspension flocculationhave been investigated. The results confirm that fibreconcentration and fibre length are the dominating factorsaffecting fibre suspension flocculation. Increasing absoluteflow velocity has an insignificant effect on fibre flocs in theflow contraction. Suppressing turbulence, by increasingsuspension viscosity via a decrease of medium temperature,shows a clear effect on reducing fibre suspensionflocculation.</p><p>Some chemical influences on fibre suspension flocculationhave also been investigated. A retention aid, flocculant,cationic polyacrylamide, C-PAM, increases fibre suspensionflocculation by a bridging mechanism, and a formation aid,class II, anionic polyacrylamide, A-PAM, decreases fibresuspension flocculation by suppressing turbulence. Fibresuspension flocculation can also be reduced by surfacemodification with carboxymethyl cellulose, due to a reductionof the friction between fibres. The amount of fibre dispersiondepends on the ionic form of the grafted CMC, due to theelectrostatic repulsion between negatively charged groups onthe grafted CMC moieties. Xyloglucan, a non-ionic polymer,which is strongly adsorbed on cellulosic fibre surfaces, showsa similar influence on reduction of fibre suspensionflocculation by decreasing the friction between fibres.</p><p>The fibre flocculation data in the flow loop system werealso compared with the corresponding paper formation data inthe sheets produced on a pilot paper machine, both with andwithout chemical additives. The results show that the fibresuspension flocculation is well correlated with the paper sheetformation: when the fibre suspension flocculation is increased,the corresponding paper sheet formation deteriorates,especially in the large scale range.</p>
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Diatezua, Jacquie Kiangebeni. "Some theoretical aspects of fibre suspension flows." Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/9707.
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Bibliography: leaves 77-82.<br>This thesis is concerned with properties of equations governing fibre suspensions. Of particular interest is the extent to which solutions, and their properties, depend on the type of closure used. For this purpose two closure rules are investigated: the linear and the quadratic closures. We show that the equations are consistent with the second law of thermodynamics, or dissipation inequality, when the quadratic closure is used. When the linear closure is used, a sufficient condition for consistency is that the particle number Np satisfies Np ≤ 35/2. Likewise, flows are found to be monotonically stable for the quadratic closure, and for the linear closure with Np ≤ 35/2. The second part of the thesis is concerned with one-dimensional problems, and their solution by finite element. The hyperbolic nature of the evolution equation for the orientation tensor necessitates a modification of the standard Galerkin-based approach. We investigate the conditions under which convergence is obtained, for unidirectional flows, with the use of the Streamline Upwind (SU) method, and the Streamline upwind Petrov/Galerkin (SUPG) method.
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Joung, Clint Gwarngsoo. "Direct simulation studies of suspended particles and fibre-filled suspensions." Thesis, The University of Sydney, 2003. http://hdl.handle.net/2123/554.
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A new Direct Simulation fibre model was developed which allowed flexibility in the fibre during the simulation of fibre suspension flow.This new model was called the 'Chain-of-Spheres' model.It was hypothesised that particle shape and deformation could significantly affect particle dynamics,and also suspension bulk properties such as viscosity.Data collected from the simulation showed that flexible fibres in shear flow resulted in an order of 7 −10% bulk relative viscosity increase over the 'rigid' fibre result.Results also established the existence of a relationship between bulk viscosity and particle stiffness. In comparison with experimental results,other more conventional rigid fibre based methods appeared to underpredict relative viscosity.The flexible fibre method thus markedly improved the ability to estimate relative viscosity.The curved rigid fibre suspension also exhibited increased viscosity of the order twice that of the equivalent straight rigid fibre suspension.With such sensitivity to fibre shape,this result has some important implications for the quality of fibre inclusions used.For consistent viscosity,the shape quality of the fibres was shown to be important. The 'Chain of Spheres' simulation was substantially extended to create a new simulation method with the ability to model the dynamics of arbitrarily shaped particles in the Newtonian flow field.This new '3D Particle' simulation method accounted for the inertial force on the particles,and also allowed particles to be embedded in complex flow fields.This method was used to reproduce known dynamics for common particle shapes,and then to predict the unknown dynamics of various other particle shapes in shear flow. In later sections, the simulation demonstrated inertia-induced particle migration in the non-linear shear gradient Couette cylinder flow,and was used to predict the fibre orientation within a diverging channel flow.The performance of the method was verified against known experimental measurements,observations and theoretical and numerical results where available.The comparisons revealed that the current method reproduced single particle dynamics with great fidelity. The broad aim of this research was to better understand the microstructural dynamics within the fibre-filled suspension and from it,derive useful engineering information on the bulk flow of these fluids.This thesis represents a move forward to meet this broad aim.It is hoped that future researchers may benefit from the new approaches and algorithms developed here.
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Joung, Clint Gwarngsoo. "Direct simulation studies of suspended particles and fibre-filled suspensions." University of Sydney. Chemical Engineering, 2003. http://hdl.handle.net/2123/554.
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A new Direct Simulation fibre model was developed which allowed flexibility in the fibre during the simulation of fibre suspension flow.This new model was called the �Chain-of-Spheres �model.It was hypothesised that particle shape and deformation could signi ficantly a ffect partic e dynamics,and also suspension bulk properties such as viscosity.Data collected from the simulation showed that flexible fibres in shear flow resulted in an order of 7 −10% bulk relative viscosity increase over the �rigid �fibre result.Results also es- tablished the existence of a relationship between bulk viscosity and particle sti ffness.In comparison with experimental results,other more conventional rigid fibre based methods appeared to underpredict relative viscosity.The flexible fibre method thus markedly improved the ability to estimate relative viscosity.The curved rigid fibre suspension also exhibited increased viscosity of the order twice that of the equivalent straight rigid fibre suspension.With such sensitivity to fibre shape,this result has some important implications for the quality of fibre inclusions used.For consistent viscosity,the shape quality of the fibres was shown to be important. The �Chain of Spheres �simulation was substantially extended to create a new simulation method with the ability to model the dynamics of arbitrarily shaped particles in the Newtonian flow field.This new �3D Particle �simulation method accounted for the inertial force on the particles,and also allowed particles to be embedded in complex flow fields.This method was used to reproduce known dynamics for common particle shapes,and then to predict the unknown dynamics of various other particle shapes in shear flow. In later sections, the simulation demonstrated inertia-induced particle migration inthe non-linear shear gradient Couette cylinder flow,and was used to predict the fibre orientation within a diverging channel flow.The performance of the method was verified against known experimental measurements,observations and theoretical and numerical results where available.The comparisons revealed that the current method reproduced single particle dynamics with great fidelity. The broad aim of this research was to better understand the microstruc- tural dynamics within the fibre-filled suspension and from it,derive useful engineering information on the bulk flow of these fluids.This thesis represents a move forward to meet this broad aim.It is hoped that future researchers may bene fit from the new approaches and algorithms developed here.
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Lindström, Stefan B. "Simulations of the Dynamics of Fibre Suspension Flows." Licentiate thesis, Mid Sweden University, Department of Natural Sciences, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-53.
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<p>A new model for simulating non-Brownian flexible fibres suspended in a Newtonian fluid has been developed. Special attention has been given to include realistic flow conditions found in the industrial papermaking process in the key features of the model; it is the intention of the author to employ the model in simulations of the forming section of the paper machine in future studies.</p><p>The model considers inert fibres of various shapes and finite stiffness, interacting with each other through normal, frictional and lubrication forces, and with the surrounding fluid medium through hydrodynamic forces. Fibre-fluid interactions in the non-creeping flow regime are taken into account, and the two-way coupling between the solids and the fluid phase is included by enforcing momentum conservation between phases. The incompressible three-dimensional Navier-Stokes equations are employed to model the motion of the fluid medium.</p><p>The validity of the model has been tested by comparing simulation results with experimental data from the literature. It was demonstrated that the model predicts the motion of isolated fibres in shear flow over a wide range of fibre flexibilities. It was also shown that the model predicts details of the orientation distribution of multiple straight, rigid fibres in a sheared suspension. Model predictions of the viscosity and first normal stress difference were in good agreement with experimental data found in the literature. Since the model is based solely on first-principles physics, quantitative predictions could be made without any parameter fitting.</p><br><p>En ny modell för simulering av rörelserna hos icke-Brownska böjliga fibrer dispergerade i en Newtonsk vätska har utvecklats. Eftersom det är författarens avsikt att modellen skall kunna tillämpas vid simulering av arkformning under de förhållanden som råder i en modern pappersmaskin, har särskilt omsorg givits till att inkludera motsvarande flödesvillkor i modellens giltighetsområde.</p><p>Modellen hanterar fibrer av varierande form, massa och styvhet, som växelverkar sinsemellan via normal-, friktions- och smörjkrafter. Deras växelverkan med den omgivande vätskan sker via hydrodynamiska krafter vid finita Reynolds-tal. Den så kallade tvåvägskopplingen mellan fibrerna och vätskefasen har tagits i beaktande genom att kräva att rörelsemängden bevaras vid interaktionen mellan faserna. Vidare har Navier-Stokes ekvationer för inkompressibla vätskor använts för att beskriva mediets rörelser.</p><p>Modellens giltighet har undersökts genom att jämföra resultat från simuleringar med experimentella data från litteraturen. Det har påvisats att modellen förutsäger rörelsen hos ensamma fibrer i ett skjuvflöde, för vitt skilda fiberflexibiliteter. Det visades också att modellen förutsäger detaljer hos fiberorienteringsdistributionen i suspensioner utsatta för skjuvflöde. Det kunde också konstateras att modellens förutsägelser av fibersuspensioners viskositet och första normalspänningsdifferens under skjuvning väl överensstämde med experimentella data i litteraturen. Kvantitativa förutsägelser har kunnat göras utan någon parameteranpassning, då modellen bygger uteslutande på väletablerade fysikaliska samband inom klassisk mekanik och strömningslära.</p>
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Kvick, Mathias. "Hydrodynamic stability and turbulence in fibre suspension flows." Licentiate thesis, KTH, Mekanik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95279.
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Raghem-Moayed, Amir. "Characterization of fibre suspension flows at papermaking consistencies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq41040.pdf.
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Holm, Richard. "Fluid mechanics of fibre suspension related to paper making." Doctoral thesis, KTH, Mechanics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-100.
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<p>This thesis deals with fluid dynamic mechanisms related to papermaking, specif- ically: the initial dewatering mechanisms during roll-forming and fibre motion in sedimentation and in shear flow. </p><p>Pressure and wire position measurements have been conducted in a model resembling the forming zone and the measured pressure distributions are shown to have more complex patterns than the simple model p / T/R (where T is the wire tension and R is the roll radius). It is shown that an increase in wire tension has a similar effect as a decrease in flow-rate on the shape of the pressure distribution. In addition, it is shown that the drainage has a stabilizing effect on the dewatering pressure. </p><p>The flow around the forming roll has also been modelled with the assump- tion that the wire is impermeable. A non-linear equation for the position of the wire is derived that clearly shows that the Weber number, We, is an im- portant parameter. The equation is linearized around the trivial solution and has a standing wave solution with a specific wavelength that scales with the We-number. </p><p>Motion of non-Brownian fibre settling in a Newtonian fluid at a small but finite Reynolds number has been studied experimentally. Two different regimes of sedimentation were identified. For dilute suspensions, fibres gener- ally fall without flipping and may travel at velocities larger than that of an isolated particle. In the semi-dilute regime we found the settling process to be dominated by large-scale fluctuations. The velocity fluctuations scale with the suspension volume concentrationφ according toφ1/3, which is similar to the findings for settling spheres. </p><p>The influence of shear on fibre orientation in the near wall region was studied in cellulose acetate fibre suspensions. At low concentration and low aspect ratio fibres were observed to orient perpendicular to the streamwise direction (named rollers) in the near wall region whereas the orientation further into the suspension was unchanged. As the concentration and aspect ratio increased the fraction of rollers decreased. </p><p>Finally, an evaluation of a commercial Ultra Velocity Profiler unit in fibre suspensions are presented. The idea was to determine the velocity and characterise the turbulence from ultra sound echoes from particles in the fluid. However, the spatial and/or temporal resolution of the measurements did not permit turbulence characterisation. These limitations might be possible to overcome and some procedures are proposed and evaluated.</p>
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Luo, Chitao. "The investigation of turbulent statistics of a fibre suspension undergoing mixing." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0001/MQ46079.pdf.
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Carlsson, Allan. "Near wall fibre orientation in flowing suspensions." Doctoral thesis, KTH, Linné Flow Center, FLOW, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9995.
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This thesis deals with fibre orientation in wall-bounded shear flows. The primary application in mind is papermaking. The study is mainly experimental,but is complemented with theoretical considerations.The main part of the thesis concerns the orientation of slowly settlingfibres in a wall-bounded viscous shear flow. This is a flow case not dealt withpreviously even at small Reynolds numbers. Experiments were conducted usingdilute suspensions with fibres having aspect ratios of rp ≈ 7 and 30. It is foundthat the wall effect on the orientation is small for distances from the wall wherethe fibre centre is located farther than half a fibre length from the wall. Farfrom the wall most fibres were oriented close to the flow direction. Closer tothe wall than half a fibre length the orientation distribution first shifted to bemore isotropic and in the very proximity of the wall the fibres were orientedclose to perpendicular to the flow direction, nearly aligned with the vorticityaxis. This was most evident for the shorter fibres with rp ≈ 7.Due to the density difference between the fibres and the fluid there is anincreased concentration near the wall. Still, a physical mechanism is requiredin order for a fibre initially oriented close to the flow direction at about half afibre length from the wall to change its orientation to aligned with the vorticityaxis once it has settled down to the wall. A slender body approach is usedin order to estimate the effect of wall reflection and repeated wall contacts onthe fibre rotation. It is found that the both a wall reflection, due to settlingtowards the wall, and contact between the fibre end and the wall are expectedto rotate the fibre closer to the vorticity axis. A qualitative agreement withthe experimental results is found in a numerical study based on the theoreticalestimation.In addition an experimental study on fibre orientation in the boundarylayers of a headbox is reported. The orientation distribution in planes parallelto the wall is studied. The distribution is found to be more anisotropic closerto the wall, i.e. the fibres tend to be oriented closer to the flow direction nearthe wall. This trend is observed sufficiently far upstream in the headbox.Farther downstream no significant change in the orientation distribution couldbe detected for different distances from the wall.<br>QC 20100706
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Zhang, Feng. "Eulerian Numerical Study of the Sedimentation of Fibre Suspensions." Licentiate thesis, KTH, Mekanik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96767.
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Sedimenting suspensions exist in a varity of natural phenomena and industrial applications. It is already observed in experiments that the dilute fibre suspensions experience a hydrodynamics instability under gravity at low Reynolds numbers. Initially well-mixed suspensions become inhomogeneous and anisotropic due to this instability.The main goal of this work is to understand the instability in a dilute fibre suspension by means of an Eulerian approach which is based on the Navier-Stokes equations coupled to Fokker-Planck equation for the PDF of fibres.Using a linear stability analysis, we show that inertia and hydrodynamic translational diffusion damp perturbations at long wavelengths and short wavelengths, respectively, leading to a wavenumber selection. For small, but finite Reynolds number of the fluid bulk motion, the most unstable wavenumber is a finite value which increases with Reynolds number, and where the diffusion narrows the range of unstable wavenumbers. With periodic boundary conditions, numerical simulations of the full non-linear evolution in time of a normal mode perturbation show that the induced flow may either die or saturate on a finite amplitude. The character of this long time behaviour is dictated by the wavenumber and the presence or absence of the translational and rotational diffusivities.In a simulation domain confined by vertical walls, a series of alternating structures of risers and streamers emerge continuously from the walls until they meet in the middle of the domain. For moderate times, this agrees qualitatively with experimental and theoretical results. Moreover, our simulation in a vessel of infinite height obtained an increasing wavelength evolution due to the congregation of the streamers or risers. In the end, there is constantly only one streamer left, and it drifts randomly to one side of the container until the evolution reaches a steady state. It is also found that the perturbations added to the initial conditions can induce more high density regions whose sizes and velocities are strongly linked to the initial perturbations of the number density or the flow field. In addition, the maximum number of streamers increases with Reynolds number, volume fraction and channel width.<br>QC 20120625
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Munganga, Justin Manango Wazute. "Existence and stability of solutions to the equations of fibre suspension flows." Doctoral thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/9728.
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Includes bibliographical references.<br>A popular approach to formulating the initial-boundary value problem for fibre suspension flows is that in which fibre orientation is accounted for in an averaged sense, through the introduction of a second-order orientation tensor A. This variable, together with the velocity and pressure, then constitutes the set of unknown variables for the problem. The governing equations are balance of linear momentum, the incompressibility condition, an evolution equation for A, and a constitutive equation for the stress. The evolution equation contains a fourth-order orientation tensor A, and it is necessary to approximate A as a function of A, through a closure relation. The purpose of this these is to examine the well-posedness of the equations governing fibre fibre suspension flows, for various closure relations. It has previously been shown by GP Galdi and BD Reddy that, for the linear closure, the problem is wellposed provided that the particle number, a material constant, is less than a critical value. The work by Galdi and Reddy made of a model in which rotary diffusivity is a function of the flow. This thesis re-examines these issues in two different ways. First, the second law of thermodynamics is used to establish the constraints that the constitutive equations have to satisfy in order to be compatible with this law. This investigation is carried out for a variety of closure rules. The second contribution of the thesis concerns the existence and uniqueness of solutions to the governing equations, for the linear and quadratic closures; for a model in which the rotary diffusivity is treated as a constant, local and global existence of solutions are established, for sufficiently small data, and in the case of the linear closure, for admissible values of the particle number. The existence theory uses a Schauder fixed point approach.
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Bland, Jonathan H. "The rheology and processing of glass mat thermoplastics." Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363537.
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Carlsson, Allan. "Orientation of fibres in suspensions flowing over a solid surface." Licentiate thesis, Stockholm : Royal Institute of Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4278.
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Fällman, Monika Carina. "Turbulence measurements in fiber suspension flows : experimental methods and results." Licentiate thesis, KTH, Mechanics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11460.
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<p>Turbulent mixing is present in many pulp and paper processes. It is a particularly important factor in the design and improvements of the paper machine headbox, influencing the final paper structure. During this project, experimental methods to quantify the effect of fibers on turbulent suspension flows have been developed, and then used for studying turbulent mixing in fiber suspensions. A technique that uses microprobes to measure passive scalar mixing of salt for the characterization of turbulent fluctuations in a fiber suspension flow has been developed: Conductivity micro-probes have been built and turbulence measurements have been performed in simple jet and wake flows, studying turbulent mixing between the two streams of pulp suspension, of which one has been doped with salt. A relatively new technique to measure fluid velocity non-intrusively in opaque fluids has also been tested. The technique makes use of ultrasonic pulses to obtain velocity information through the Doppler-shift of reflected pulses. The main efforts reported on in the thesis are focused on method design and development as well as method evaluation.</p>
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Hirota, Masato. "An Experimental Study of Fibre SuspensionFlows in Pipes using Nuclear MagneticResonance Imaging." Thesis, KTH, Mekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202628.
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This study deals with fibre suspension flows through cylindrical pipes. Thepresent work aims at measurements of opaque flows, which are common inindustries. Nuclear magnetic resonance imaging (NMRI) and ultrasound velocimetryprofiling (UVP) were employed as non-invasive and optic-independenttools to measure the velocity profiles. As a first experiment, a paper-pulp suspensionflow through a sudden contraction and expansion was investigated.The results show the NMRI technique can be used to measure the stronglyunsteady flow such as separated regions though the MR signal is attenuateddue to the turbulence in the flow. The flow loop had however an insufficientinlet length which caused asymmetric profiles at the test section. As a secondexperiment, a flow loop which provided fully developed flows at the test sectionwas designed. After that, the velocity profiles of rayon-fibre and micro-spheresuspension flows were measured by the NMRI and the UVP independently.In principle, these two techniques measure the different velocities of the fibresuspensionflows, i.e. the velocity of the water and the fibre. In dilute suspensionflows, where the velocities of the two phases were assumed to be thesame, the velocity profiles were in good agreement. This shows the validityof the two measurement techniques. However, it should be pointed out thatthere is a limitation of the current UVP method for highly concentrated flows.The velocity profiles obtained by the UVP at high concentrations seems notto represent physics while the NMRI is not affected by the concentrations. Itis argued that the advances of the NMRI for the measurement of the highlyconcentrated flows.
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Bergström, Jonas. "Flow Field and Fibre Fractionation Studies in Hydrocyclones." Doctoral thesis, KTH, Fiber- och polymerteknik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4175.
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Hydrocyclones can be used to fractionate fibres according to their papermaking potential. The obtained fractions typically differ in fibre wall thickness and/or degree of fibre treatment. Despite a multitude of potential application scenarios, the process has so far had little commercial success. This is largely explained by the low fractionation efficiency and unfavourable operating characteristics of the process. The fractionation efficiency of a hydrocyclone is closely related to its flow field. The influence of pulp concentration on the tangential velocity field was therefore studied, by using a self-cleaning pitometer. It was found that the pulp concentration had a strong influence on the tangential velocity. At a feed pulp concentration above 7.5 g/l, the suspension rotated almost as a solid body. As a consequence, the magnitude of radial acceleration and shear stresses decreased dramatically. It is suggested that this is detrimental to the fractionation efficiency. The radial velocity field was measured using an Ultrasonic Velocity Profiler. The measurements showed that the rotational centre of the flow field did not correspond with the geometrical centre of the hydrocyclone. This displacement caused the tangential velocity component of the vortex to contribute substantially to the measurement result of the radial velocity component. Based on the findings in respect to the flow field studies, a novel design for a fibre fractionation hydrocyclone was proposed. The flow field inside this hydrocyclone was compared to that in a conventional hydrocyclone. It was found, that high radial acceleration and shear stresses could be maintained in the novel design even at high fibre concentration. The fractionation efficiency of the novel hydrocyclone was characterised in terms of surface roughness difference between fine and coarse fraction. When operated with refined bleached softwood kraft pulp, the novel hydrocyclone could produce fractions with a substantial surface roughness difference without deteriorating the dewatering characteristics of the fine fraction. A low thickening of the reject is proposed to be the explanation for that. When fractionating TMP, the best efficiency occurred at a concentration of 10 g/l.<br>QC 20100804
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Bouhabila, El Hani. "Epuration d'eaux usées par bioréacteur aéré à membranes immergées : intéraction suspension floculée / membrane." Toulouse, INSA, 1999. http://www.theses.fr/1999ISAT0023.
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Cette étude est consacrée à la caractérisation du fonctionnement d’un bio réacteur à membranes à fibres creuses immergées pour l’épuration d’eau usée domestique ou d’un effluent synthétique. Les paramètres qui ont caractérisé le fonctionnement du bio réacteur à membrane sont l’âge de la boue( 10, 20 et 30 jours) et la charge volumique appliquée. Malgré la présence de composés difficilement biodégradables dans l’effluent à traiter, le rendement d’élimination de composés organiques était supérieur à 90% même pour une charge volumique de 5,7 Kg DCO/m3. J. La membrane a prouvé son rôle dans l’élimination des composés organique était associée une nitrification presque complète. Dans ces conditions, les mécanismes du métabolisme endogène sont amplifiés, ce qui a conduit à une réduction de la production des boues estimée à 0,15 KgMES/KgDCO éliminée pour un âge de boue de 30 jours. En revanche, un colmatage des membranes accompagne ces performances. Le surnageant obtenu après centrifugation des boues joue un rôle très important dans ce colmatage : il est responsable de 75% de la résistance au colmatage. L’augmentation de l’âge de la boue réduit le colmatage dû à cette fraction. L’utilisation combinée de l’aération à un débit de 1,8 m3/h et du rétro lavage à une fréquence de 15s chaque 15 min permet de multiplier la perméabilité des membranes par un facteur 7
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Hyensjö, Marko. "Fibre Orientation Modelling Applied to Contracting Flows Related to Papermaking." Doctoral thesis, KTH, Mekanik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4762.
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The main goal of this work was to develop numerical models for studying the behaviour of fibres in an accelerated flow. This is of special interest for e.g. papermaking. The early stage of the paper manufacturing process determines most of the final properties of a paper sheet. The complexity of studying the flow of fibre suspensions both experimentally and numerically emphasises a need for new ideas and developments. By means of solving the evolution of a convective-dispersion equation, i.e. the Fokker-Planck equation, a fully 3D approach with respect to the position and the two fibre angles, polar and azimuthal angles, following a streamline is presented. As an input to the fibre orientation model the turbulent flow field is solved by Computational Fluid Dynamics (CFD) with second-order closure in the turbulence model. In this work two new hypotheses have been presented for the variation of the non-dimensional rotational diffusivity with non-dimensional fibre length, Lf /η and the Reynolds number based on the Taylor micro-scale of the turbulence, Reλ Parameters for the two new hy- potheses and earlier models are determined with the aim of achieving a general relation and a value of the rotational dispersion coeffcient of stiff fibres in an anisotropic turbulent fluid flow. Earlier modelling work has been focused on solving the planar approach, i.e. assuming all fibres to be in one plane. This planar approach is discussed and compared with the fully 3D approach and its validity is evaluated. The optimization of parameters for the different hypotheses correlated on a central streamline, showed a good agreement with an independent experimental result in the undisturbed region. Moreover, it is particularly interesting that the boundary layer region and the wake region are predicted fairly well and the phenomena are well described, which has not been the case earlier. It seems that the new hypothesis based on the variation of the non-dimensional fibre length, Lf /η gives the best correlation in these shear-layer regions. Further- more it was established that the planar approach fails to predict shear layers, i.e. the boundary layer and the wake regions. As emphasized in the theory section, the planar formulation is strictly valid only if all fibres are oriented in one plane, which is not the case in the shear layers. In the undisturbed region, the 3D and the planar approaches, agree in their results. This leads to the conclusion that both approaches are suitable when shear layers are not studied.<br>QC 20100812
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Lindström, Stefan. "Modelling and simulation of paper structure development." Doctoral thesis, Mittuniversitetet, Institutionen för naturvetenskap, teknik och matematik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-7003.
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A numerical tool has been developed for particle-level simulations of fibre suspension flows, particularly forming of the fibre network structure of paper sheets in the paper machine. The model considers inert fibres of various equilibrium shapes, and finite stiffness, interacting with each other through normal, frictional, and lubrication forces, and with the surrounding fluid medium through hydrodynamic forces. Fibre–fluid interactions in the non-creeping flow regime are taken into account, and the two-way coupling between the solids and the fluid phases is included by enforcing momentum conservation between phases. The incompressible three-dimensional Navier–Stokes equations are employed tomodel themotion of the fluid medium. The validity of the model has been tested by comparing simulation results with experimental data from the literature. It was demonstrated that the model predicts well the motion of isolated fibres in shear flow over a wide range of fibre flexibilities. It was also shown that the model predicts details of the orientation distribution of multiple, straight, rigid fibres in a sheared suspension. Furthermore, model predictions of the shear viscosity and first normal stress difference were in fair agreement with experimental data found in the literature. Since the model is based solely on first principles physics, quantitative predictions could be made without any parameter fitting. Based on these validations, a series of simulations have been performed to investigate the basic mechanisms responsible for the development of the stress tensor components for monodispersed, non-Brownian fibres suspended in a Newtonian fluid in shear flow. The effects of fibre aspect ratio, concentration, and inter-particle friction, as well as the tendency of fibre agglomeration, were examined in the nonconcentrated regimes. For the case of well dispersed suspensions, semi-empirical relationships were found between the aforementioned fibre suspension properties, and the steady state apparent shear viscosity, and the first/second normal stress differences. Finally, simulations have been conducted for the development of paper structures in the forming section of the paper machine. The conditions used for the simulations were retrieved from pilot-scale forming trial data in the literature, and from real pulp fibre analyses. Dewatering was simulated by moving two forming fabrics toward each other through a fibre suspension. Effects of the jet-to-wire speed difference on the fibre orientation anisotropy, the mass density distribution, and three-dimensionality of the fibre network, were investigated. Simulation results showed that the model captures well the essential features of the forming effects on these paper structure parameters, and also posed newquestions on the conventional wisdom of the forming mechanics.
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Lowys, Marie-Pierre. "Comportement physico-chimique de suspensions de fibres cellulosiques : rôle des additifs." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10195.
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Ce travail porte sur la caracterisation physico-chimique de suspensions aqueuses de microfibrilles de cellulose (mfc) issues de la transformation des betteraves sucrieres, seules ou en presence d'additifs. La composition chimique des suspensions meres de mfc est determinee : elles sont composees de 86% de cellulose pure, les 14% restant etant des pectines, des hemicelluloses et des sels. Les proprietes ioniques des mfc sont ensuite etudiees par differentes techniques (conductimetrie, potentiel d'ecoulement, potentiel zeta). L'etat de dispersion des suspensions a ete caracterise par des mesures rheologiques en ecoulement et de sedimentation, qui ont mis en evidence l'importance du mode de dispersion et de la concentration en mfc sur la stabilite des suspensions. Nous avons montre l'existence d'une concentration critique c* au-dela de laquelle les suspensions ont un comportement de type gel. Des echantillons de mfc seches sous forme de film ne permettent pas de recuperer les proprietes rheologiques initiales lors de la remise en suspension. L'etude du comportement rheologique dynamique, montre que la remise en suspension est satisfaisante si un additif anionique est ajoute aux mfc avant sechage. L'etude de l'adsorption et de la desorption de ces additifs et des observations en microscopie de fluorescence, montrent que l'adsorption se fait de maniere uniforme sur toute la surface des mfc, mais que les interactions mises en jeu sont faibles, totalement reversibles. L'adsorption depend fortement de la charge et de la structure chimique de l'additif, mais pas de sa masse molaire. Ces resultats conduisent a l'hypothese de la formation d'un film interfacial d'additif anionique parfaitement hydrosoluble autour des mfc lors du sechage, permettant la remise en suspension et la recuperation des proprietes rheologiques de la suspension initiale. Certaines proprietes des suspensions de mfc ont ete comparees a celles de suspensions d'une cellulose bacterienne.
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Bellani, Gabriele. "Velocity measurements in a fiber suspension flow : formation of a fiber network /." Licentiate thesis, Stockholm : KTH Mechanics, Royal Institute of Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9382.
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Söderberg, Daniel. "Hydrodynamics of plane liquid jets aimed at applications in paper manufacturing." Doctoral thesis, KTH, Mekanik, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2839.
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Process industries are in general depending, in one way or the other, on fluid mechanics.Specifically, paper manufacturing, which probably is the dominant processindustry in Sweden, is depending on the flow of cellulose fibres suspended in water.As a part of the process the suspension, consisting of fibres in water, is spread out onor between two moving permeable weaves, i.e. wires. The speed of this is usually 10–30 m/s and the suspension is spread out by a plane jet issuing from a headbox nozzle.It has been show that the conditions in the headbox and jet have a large influence onthe quality of the final paper sheet. Primarily, streaks in the paper sheet are believedto be the result of streamwise streaks in the headbox jet.The thesis is aimed at the flow phenomena which occur in the headbox jet. Theinvestigations have been made with numerical calculations, stability theory and modelexperiments using water, as well as experiments with a real paper machine headboxand fibre suspension. In the thesis an introduction to the hydrodynamics of planeliquid jets is presented together with a description of the paper forming process andthe fluid mechanics of headbox flow.The basic flow and stability of a two-dimensional plane liquid jet has been investigatedby numerical calculations, stability theory and experiments. The calculationsof the laminar basic flow is successfully compared to pitot-tube measurements of thestreamwise velocity profile. By visualisations of the flow it is found that wave disturbanceson the jet has a severe effect on the flow. These waves can be predicted bylinear stability theory, which shows the presence of five convectively unstable modes.These can be divided into three types and by comparison with the experiments thetype of the visible waves is determined. These waves seem to initiate a break-up ofthe jet, which leads to strong streamwise streaks inside the jet.By flow visualisation of headbox flow of an experimental paper machine, togetherwith analysis of the resulting paper structure using the wavelet method the correspondencebetween flow disturbances and paper quality was investigated. It was shownthat the wave instability, which is present on the low Reynolds number water jet, alsocan be found in the real the headbox jet. It is shown that these waves play an importantrole in the dynamics of the headbox jet and also have an influence on the final papersheet.<br>QC 20100825
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Paterson, Daniel Thomas. "Understanding rapid dewatering of cellulose fibre suspensions." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58195.
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Rapid dewatering of cellulose fibre suspensions is a fundamental process in many unit operations in the production of pulp and paper. Understanding dewatering behaviour can be applied to optimizing designs of industrial equipment. In this project, we assess the suitability of a well-established modeling approach, referred to as the base model, at capturing the one dimensional dewatering behaviour of cellulose fibre suspensions seen experimentally. This modeling approach requires two closure relationships determined experimentally, i.e. compressive yield stress and permeability. Experimental equipment has been designed, constructed, and operated to obtain the closure relationships and collect dewatering results for validation of the model. Two experimental techniques, with close agreement, have been developed for the collection of compressive yield stress. Permeability results are obtained through Darcian permeation experiments. Two approaches, neglecting and accounting for flow induced compaction, were developed. Results were found to fall within values seen in the literature. The base model provided good representation of ideal nylon fibre suspension trials. These solid fibres are representative of the base models constitutive equation for an infinite solid phase rearrangement rate constant. The base model poorly represents the cellulose fibre suspensions' dewatering behaviour. The suggested source of discrepancy is the further dynamic due to the dewatering of the individual porous cellulose fibres which results in a finite solid phase rearrangement rate constant. The base model is expanded upon in hopes of capturing this rate dependent behaviour. This extended model, with the determined closure relationships, captured load versus solid volume fraction profiles at varying dewatering rates better than the base model for cellulose fibre suspensions. Further improvements in representation were seen through close representation of the solid phase velocity profiles found experimentally during dewatering. Various cellulose fibre suspensions were investigated to begin a catalog of different dewatering behaviours seen through variations in pulp production variables. Investigations included varying fibre species, pulping processes, levels of low consistency refining, and impacts of dewatering chemical additives.<br>Applied Science, Faculty of<br>Mechanical Engineering, Department of<br>Graduate
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Fletcher, Paul E. "Electrically assisted fibre filtration of aqueous suspensions." Thesis, Cranfield University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359519.
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Sykes, Paul. "Lubrication flows of semi-dilute fibre suspensions." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627460.
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Férec, Julien. "Étude et modélisation du comportement rhéologique de suspensions de fibres rigides en régime non-dilué." École polytechnique de Montréal, 2008. http://www.theses.fr/2008LORIS116.
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De nombreuses recherches se sont intéressées aux comportements des suspensions de fibres en cisaillement simple (transitoire et permanent) et dynamique (petites déformations). Cependant le comportement élongationnel et la connaissance de leurs propriétés rhéologiques en grandes déformations oscillatoires sont d’un grand intérêt. Les résultats oscillatoires en grandes déformations montrent que pour des polypropylènes renforcés de fibres de verre courtes, l’amplitude de la contrainte en cisaillement diminue graduellement. Un comportement inverse est observé pour une matrice en polybutène. Pour ces deux matrices, les premières différences de contraintes normales sont sensibles aux orientations des fibres. Les observations réalisées en élongation indiquent que la présence des fibres dans un polypropylène augmente sa viscosité. En régime transitoire, différentes orientations initiales des fibres ont été préparées. La dynamique d’orientation des charges provoque un léger rhéoépaississement sous déformation. En régime établi, la viscosité élongationnelle a été comparée par trois appareillages différents. Une méthode basée sur les volumes finis a été utilisée pour résoudre numériquement l’équation de Fokker-Planck pour la fonction de distribution d’orientation. Les résultats sont tels que les temps de calcul sont réduits de façon considérable. Finalement, un modèle rhéologique a été développé où l’attention porte sur une modélisation plus précise des interactions fibre-fibre. Une nouvelle équation d’évolution est proposée où le terme de diffusion est proportionnel au nombre moyen de contacts entre les fibres. Le modèle a été validé par des mesures expérimentales<br>Several studies have investigated the behavior of fiber suspensions in simple shear (transient and steady) and oscillatory shear (small deformations) flows. However, the rheological behavior of fiber-filled fluids subjected to elongational and large amplitude oscillatory shear flows may be of great interest. Results from large amplitude oscillatory shear flow showed that for short glass fiber reinforced polypropylene the shear stress amplitude decreased gradually. An opposite behavior was observed for a reinforced polybutene matrix. The primary normal stress differences of the two matrices are sensitive to fiber orientation. The observations carried out in elongational flow indicated that the presence of fibers in polypropylene increased its viscosity. For transient tests, various initial fiber orientations were prepared. The fiber orientation dynamics caused a slight strain hardening behavior. The steady state elongational viscosity data obtained using three different equipments have been compared. A finite volume method has been used to solve numerically the Fokker-Planck equation for the probability distribution function. The results are such that the computational time is considerably reduced. The last point tackled in this work concerns the development of a rheological model with a more precise modeling of fiber-fiber interactions. A new time evolution equation is proposed, where the diffusion term is proportional to the average number of contacts between fibers. The model is validated using experimental data
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Bibbó, Miguel Angel. "Rheology of semiconcentrated fiber suspensions." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14875.
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Holm, Richard. "Fluid mechanics of fibre suspensions related to papermaking." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-100.
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Derakhshandeh, Babak. "Rheology of low to medium consistency pulp fibre suspensions." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/37371.
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Papermaking is a major industry to manufacture products vital to education, communication, and packaging. Most operations in this industry deal with the flow of different mass concentrations of pulp suspensions. Therefore, the flow properties (rheology) of pulp suspensions are of great importance for the optimal functionality of most unit operations in the industry.
Yield stress is one of the most important rheological properties in designing process equipment, thus needs to be determined by a reliable technique. Two established and extensively used methods for determining yield stress were compared with a velocimetry technique. The yield stresses were determined for commercial pulp suspensions at fibre mass concentrations of 0.5 to 5 wt. %. The results were compared and models were proposed to predict the yield stress as a function of fibre mass concentration. The yield stress values obtained by the velocimetry technique were found to be the most reliable.
Conventional rheometry and local velocimetry techniques were further used to study the flow behaviour of pulp suspensions beyond the yield stress. Pulp suspensions were found to be shear-thinning up to a certain high shear rate. The Herschel–Bulkley constitutive equation was used to fit the local steady-state velocity profiles and to predict the steady-state flow curves obtained by conventional rheometry. Conventional rheometry was found to fail at low shear rates due to the presence of wall slip. Consistency between the various sets of data was found for all suspensions studied.
Finally, the same approach was used to study thixotropy and transient flow behaviour of concentrated pulp suspension of 6 wt.%. Pulp was found to exhibit a plateau in the flow curve where a slight increase in the shear stress generated a jump in the corresponding shear rate, implying the occurrence of shear banding. The velocity profiles were found to be discontinuous in the vicinity of the yielding radius where a Herschel-Bulkley model failed to predict the flow. Shear history and the time of rest prior to the measurement were found to play a significant role on the rheology and the local velocity profiles of pulp suspension.
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Fan, Xijun. "Numerical study on some rheological problems of fibre suspensions." Thesis, The University of Sydney, 2006. http://hdl.handle.net/2123/1096.
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This thesis deals with numerical investigations on some rheological problems of fibre suspensions: the fibre level simulation of non-dilute fibre suspensions in shear flow; the numerical simulation of complex fibre suspension flows and simulating the particle motion in viscoelastic flows. These are challenging problems in rheology. Two numerical approaches were developed for simulating non-dilute fibre suspensions from the fibre level. The first is based on a model that accounts for full hydrodynamic interactions between fibres, which are approximately calculated as a superposition of the long-range and short-range hydrodynamic interactions. The long-range one is approximated by using slender body theory and includes infinite particle interactions. The short-range one is approximated in terms of the normal lubrication forces between close neighbouring fibres. The second is based on a model that accounts only for short-range interactions, which comprise the lubrication forces and normal contact and friction forces. These two methods were applied to simulate the microstructure evolution and rheological properties of non-dilute fibre suspensions. The Brownian configuration method was combined with the highly stable finite element method to simulate the complex flow of fibre suspensions. The method is stable and robust, and can provide both micro and macro information. It does not require any closure approximations in calculating the fibre stress tensor and is more efficient and variance reduction, compared to CONNFFESSITT, for example. The flow of fibre suspensions past a sphere in a tube and the shear induced fibre migration were successfully simulated using this method The completed double layer boundary element method was extended to viscoelastic flow cases. A point-wise solver was developed to solve the constitutive equation point by point and the fixed least square method was employed to interpolate and differentiate data locally. The method avoids volume meshing and only requires the boundary mesh on particle surfaces and data points in the flow domain. A sphere settling in the Oldroyd-B fluid and a prolate spheroid rotating in shear flow of the Oldroyd-B fluid were simulated. Based on the simulated orbit of a prolate spheroid in shear flow, a constitutive model for the weakly viscoelastic fibre suspensions was proposed and its predictions were compared with some available experimental results. All simulated results are in general agreement with experimental and other numerical results reported in literature. This indicates that these numerical methods are useful tools in rheological research.
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Fan, Xijun. "Numerical study on some rheological problems of fibre suspensions." School of Aerospace, Mechanical & Mechatronic Engineering, 2006. http://hdl.handle.net/2123/1096.
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Doctor of philosophy (Ph D)<br>This thesis deals with numerical investigations on some rheological problems of fibre suspensions: the fibre level simulation of non-dilute fibre suspensions in shear flow; the numerical simulation of complex fibre suspension flows and simulating the particle motion in viscoelastic flows. These are challenging problems in rheology. Two numerical approaches were developed for simulating non-dilute fibre suspensions from the fibre level. The first is based on a model that accounts for full hydrodynamic interactions between fibres, which are approximately calculated as a superposition of the long-range and short-range hydrodynamic interactions. The long-range one is approximated by using slender body theory and includes infinite particle interactions. The short-range one is approximated in terms of the normal lubrication forces between close neighbouring fibres. The second is based on a model that accounts only for short-range interactions, which comprise the lubrication forces and normal contact and friction forces. These two methods were applied to simulate the microstructure evolution and rheological properties of non-dilute fibre suspensions. The Brownian configuration method was combined with the highly stable finite element method to simulate the complex flow of fibre suspensions. The method is stable and robust, and can provide both micro and macro information. It does not require any closure approximations in calculating the fibre stress tensor and is more efficient and variance reduction, compared to CONNFFESSITT, for example. The flow of fibre suspensions past a sphere in a tube and the shear induced fibre migration were successfully simulated using this method The completed double layer boundary element method was extended to viscoelastic flow cases. A point-wise solver was developed to solve the constitutive equation point by point and the fixed least square method was employed to interpolate and differentiate data locally. The method avoids volume meshing and only requires the boundary mesh on particle surfaces and data points in the flow domain. A sphere settling in the Oldroyd-B fluid and a prolate spheroid rotating in shear flow of the Oldroyd-B fluid were simulated. Based on the simulated orbit of a prolate spheroid in shear flow, a constitutive model for the weakly viscoelastic fibre suspensions was proposed and its predictions were compared with some available experimental results. All simulated results are in general agreement with experimental and other numerical results reported in literature. This indicates that these numerical methods are useful tools in rheological research.
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Hammarström, David. "A Model for Simulation of Fiber Suspension Flows." Licentiate thesis, KTH, Mechanics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1744.
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<p>The fiber suspensions in the production line from wood topaper are subjected to many types of chemical and mechanicalprocesses, in which the flow of the suspension is of vitalimportance. The flow of the suspension determines the degree ofuniformity of the fibers through the processing, which inreturn affects the properties of the fiber suspension. In orderto optimise the process, thorough knowledge of the suspensionflow is necessary, both on the level of suspension, fibernetworks and individual fibers. Knowledge of the fibersuspension behaviour combined with commercial CFD simulationprovides an efficient design method for any unit operation inthe papermaking process.</p><p>This work concentrates on macroscopic modeling of thebehaviour of fiber suspensions from 0.5-5% dry content, purefiber suspensions without fillers or additives. Any mechanismscausing the characteristic behaviour of the pulp suspensionhave not been included, they are only included through theirinfluence on the suspension parameters. Excluded mechanismsare, for instance, the fiber-fiber coupling mechanisms that arethe reason for the formation of fiber networks and parts offiber network, flocs.</p><p>By combining a rheology model for the bulk suspension, awall function that accounts for the slip layer and finallyintroducing turbulence, a model has been created that is ableto simulate the flow of most fiber suspensions. The flow of thesuspension is not constrained to any particular flowconditions; the models discussed in this work aim at describingthe behaviour of the suspension for all flow rates and flowtypes. The models are developed under simple flow conditions,where all variables can be controlled, but the models areintended for usage within the industry-based flows in real pulpand papermaking applications.</p><p><b>Keywords:</b>rheology, fiber, suspension, CFD, model, wall,slip, turbulence</p>
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Salahuddin, Asif. "Orientation and rotational diffusion of fibers in semidilute suspension." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41163.
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The dynamics of fiber orientation is of great interest for efforts to predict the microstructure and material properties of a suspension flow system. In this research a fiber-level, hybrid simulation method, LBM‒EBF (coupled lattice‒Boltzmann method with the external boundary force method) is undertaken to advance the current understanding of the hydrodynamic interaction induced rotational diffusion mechanism for rigid fibers in semidilute suspension of low Reynolds number flow. The LBM‒EBF simulations correctly predict the orbit constant distribution of fibers in a sheared semidilute suspension flow. It is demonstrated that an anisotropic, weak rotary diffusion model can fit the orbit constant distribution very well, but it can not describe the asymmetry in Stokes flow observed in semidilute suspension. The rotational diffusion process is then characterized with a three dimensional spatial tensor representation of the rotational diffusivity. A scalar measure of the rotational diffusion‒'scalar Folgar‒Tucker constant', C[subscript I], is extracted from this tensor. The study provides substantial numerical evidence that the range of C[subscript I] (0.0038 to 0.0165) obtained by Folgar&Tucker (J. reinf. plast. and comp, v.3, 1984) in a semidilute regime is overly diffusive, and that the correct magnitude is of O(10⁻⁴). The study reveals that the interactions among fibers become more frequent with either the decrease of fiber aspect-ratio, r[subscript p] (keeping nL³ constant, where n is the fiber number density, and L is the fiber length) or with the increase of nL³ (keeping r[subscript p] constant) in the semidilute regime, which in consequence causes an increase in C[subscript I]. The rheological properties of sheared semidilute suspension are also computed with direct LBM‒EBF simulations. The LBM‒EBF investigation is extended to characterize the fiber orientation in a linearly contracting channel similar to a paper machine 'headbox'. It is found that the rotational diffusion is the predominant term over the strain rate in the semidilute regime for a low Reynolds number flow, and it results in a decreasing trend of rotational Peclet number, Pe, along the contraction centerline. Lastly, in order to improve the numerical consistency of the existing LBM‒EBF approach, a modification to the body force term in the LB equation is suggested, which can recover the exact macroscopic hydrodynamics from the mesoscale.
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Joung, Clint G. "Direct simulation studies of suspended particles and fibre-filled suspensions." Connect to full text, 2003. http://hdl.handle.net/2123/554.
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Thesis (Ph. D.)--University of Sydney, 2004.<br>Title from title screen (viewed 16 April 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Aerospace, Mechanical and Mechatronic Engineering. Degree awarded 2004; thesis submitted 2003. Contains published article co-authored by Joung. Includes bibliographical references. Also available in print form.
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Krochak, Paul Joseph. "The orientation state of semi-dilute rigid fibre suspensions in a linearly contracting channel." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/842.
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This work investigates the effects of long range hydrodynamic fibre-fibre interactions on the orientation state of a semi-dilute, rigid fibre suspension flowing through a linear contracting channel under laminar flow conditions. The effects of fibre-fibre interactions are modeled mathematically, the governing equations solved numerically and the predicted results compared with experimental observations.
The theoretical model is based on the assumption that the orientation state of the suspension can be completely described by a probability distribution function and that fibre-fibre interactions are random in nature, thus giving rise to a diffusion-type process. The orientation distribution evolves spatially according to a Fokker-Plank type equation using closure equations for the rotary diffusion coefficient advanced by either (i) Folgar and Tucker (J. Reinforced Plast. Comp. 3 98–119 1984) or (ii) Koch (Phys. Fluids 7(8) 2086–2088 1995). Each of these two closure models for the rotary diffusion coefficient contains an unknown empirical constant that must be determined from experiments. These were fit to experimental data along the central streamline of the contraction as a function of fibre concentration. The diffusion coefficient was found to first increase with increasing suspension concentration up to a maximum, and then decrease with concentration above this point. This non-monotonic behavior was attributed to fibre flocculation, a mechanism not considered in the relationships for the rotary diffusion coefficient. The theoretical model is then extended to predict fibre orientation over the entire plane of the contraction and the two-way momentum coupling between the fluid and fibre phases were investigated numerically. The results show that the structure of the flow field within the contraction is significantly altered when the fibre phase is considered, demonstrating the non-negligible effect of the momentum exchange between the two phases. Comparison is made between the predicted orientation state of the suspension with experimental observations over the contraction plane. Good agreement was found between the model predictions and the experimental observations except in a small region near the solid boundaries. These near wall discrepancies were attributed to an inability to correctly handle the wall boundary conditions in the fibre orientation model.
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Soszyński, Robert Marian. "The formation and properties of coherent flocs in fibre suspensions." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27544.
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Fibres in concentrated suspensions are in continuous contact with other fibres and may interlock through elastic bending to form coherent networks. Such interlocking is termed Type-C cohesion. The process by which Type-C cohesion forms among fibres and the resulting structure and tensile strength of individual floes of fibres have been examined in experimental study in which relatively straight, smooth nylon (6-6) fibres of aspect ratios from 65 to 189 were suspended in aqueous-sugar solutions. The fibres were in most cases neutrally buoyant. The suspensions were caused to flow in a partially filled, inclined-to-the-horizontal or horizontally-oriented cylinder rotated about its principal axis to produce a recirculating and moderately unsteady flow. At a well-defined and reproducible "threshold concentration" Type-C coherent floes formed. The floes were verified to be of Type-C by heat treatment. The heat treatment caused stress relaxation in elastically bent fibres resulting in reduced floe strength. Visual observations of floe formation and velocity measurements with Laser Doppler Anemometer indicated that the floes originated in the zone in which flow decelerated. In this zone floes formed by compaction of crowded fibres. The threshold concentration depended on fibre geometry and viscosity of the suspending liquid. Below an aspect ratio of approximately 50 and above a suspending liquid viscosity of approximately 0.013 Pa‧s, Type-C coherent floes did not form at any concentration of fibres. Under the test conditions of this work, the threshold concentration was unaffected by the cylinder rotational speed, cylinder diameter, and angle of incline to the horizontal, provided that sufficient shear was induced in the cylinder to create recirculating flow. The structure and strength of Type-C coherent floes were examined. The number of contact points per fibre was less than values estimated from theoretical, statistical models in the literature. The tensile strength of individual Type-C floes measured in a tester with a unique comb support showed values larger than strengths reported in the literature for either man-made or wood-pulp fibre networks. A mathematical model developed to describe tensile strength based on frictional fibre-to-fibre interaction accounted for only a part of the total floe strength.<br>Applied Science, Faculty of<br>Chemical and Biological Engineering, Department of<br>Graduate
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Plikas, Atanasis. "Numerical modeling of fibre suspensions in grid-generated turbulent flow." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0023/MQ50361.pdf.
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Guiraud, Olivier. "Rhéologie des suspensions concentrées de fibres : application à la mise en forme des matériaux composites." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00680734.
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Cette étude porte sur la mise en forme des matériaux composites renforcés par des fibres ou des mèches de fibres courtes tels que les SMC ou les BMC. Un travail expérimental a dans un premier temps été réalisé à l'échelle macroscopique. Ce travail a permis de mettre au point un rhéomètre de compression lubrifiée ainsi que des méthodes d'essais et de dépouillement. Ceci permet de mieux caractériser la rhéologie des compounds SMC et BMC en traitant les problématiques de leur compressibilité et des frottements éventuels entre les parois du rhéomètre et la matière déformée. Un travail numérique a ensuite permis de simuler la mise en forme d'un BMC après l'identification des paramètres d'un modèle rhéologique simple à partir des données expérimentales obtenues sur le rhéomètre. Enfin, un travail expérimental à l'échelle microscopique a permis d'une part de caractériser finement les microstuctures de SMC modèles à partir de microtomographies à rayons X, et d'autre part de caractériser et de modéliser par le biais d'essais d'extraction de fibres les interactions entre les mèches formant le renfort fibreux de ces matériaux.
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Ruys, Victor. "Rhéologie des résidus agricoles pour un procédé multi-étapes de méthanisation en voie sèche." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI064/document.
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Rhéologie des résidus agricoles pour un procédé de méthanisation par voie sèche multi-étapes.Le procédé Arkométha® utilise à profit l’injection de biogaz pour mélanger les résidus agricoles (fumier, lisier, ensilage, etc…) lors d’un procédé de méthanisation en voie sèche dans lequel la matière est épaisse. La connaissance des propriétés rhéologiques de ces matériaux, rarement étudiés dans la littérature, notamment à l’échelle industrielle, est un élément indispensable pour maitriser et contrôler le processus de mélange. Cette thèse a pour objectif de développer la compréhension des évolutions physiques et rhéologiques de ces matériaux lors de la méthanisation. La revue bibliographique détaillée dans le deuxième chapitre, a montré la nécessité de disposer d’un rhéomètre capable de mesurer les propriétés rhéologiques de ces produits à l’échelle industrielle. Pour cela, un cahier de charge a été établi à partir des contraintes scientifiques et techniques imposées par ces matériaux considérés comme des suspensions concentrées en fibres de dimensions importantes. Sur cette base, un rhéomètre de grandes dimensions pour les substrats, nommé RGDS, a été construit, validé et mis en service sur site industriel. La technique de scissométrie était utilisée pour mesurer le seuil d’écoulement et des pales type mélangeur, étalonnées en utilisant l’analogie de Couette, permettent de mesurer les propriétés sous écoulement. Dans le troisième chapitre nous avons montré la limite de l’utilisation du taux de matière sèche (MS%) traditionnellement utilisé comme un paramètre contrôlant la rhéologie, comme par exemple, le seuil d’écoulement de ces matériaux. Nous avons montré qu’il est plus pertinent de maitriser la répartition de l’eau dans la suspension pour contrôler les propriétés rhéologiques en prenant en compte le caractère spongieux de la matière lignocellulosique. Nous avons montré comment déterminer les concentrations critiques qui séparent les régimes semi-concentré, concentré, milieu triphasique non saturé en liquide jusqu’à un milieu granulaire humide et leurs relations avec le seuil d’écoulement. Dans le quatrième chapitre nous avons étudié l’effet de l’évolution des paramètres opératoires du procédé de méthanisation comme la taille des fibres, la température et le taux de matière sèche sur les propriétés rhéologiques des matériaux. Plusieurs modèles et lois ont été proposés pour quantifier l’intérêt d’effectuer des modifications des paramètres opératoires sur la rhéologie de ces matériaux<br>The Arkometha® process uses biogas injections to mix agricultural residues (manure, slurry, silage, straw) in a dry anaerobic digestion process. Knowledge of the rheological properties of these materials, rarely studied in the literature, and especially not on an industrial scale, is an essential element to supervise and control the mixing process. This thesis aims to improve the understanding of the physical and rheological evolutions of these materials along the anaerobic digestion process. The literature showed the need for a rheometer able to measure the rheological properties of these products at the industrial scale. For this purpose, specifications were established based on the scientific and technical constraints imposed by these materials, which are considered as fiber concentrated suspensions. On this basis, a large rheometer for substrates, called RGDS for (Rheometer Grand Dimensions for the Substrate), was built, validated and commissioned on an industrial site. The van test technique was used to measure the yield stress and mixer blades, calibrated using the Couette analogy, were used to measure shear stresses. In the third chapter we have shown the utilization limits of the total solids (TS%), traditionally used as the main parameter for rheology controlling. In this chapter we treated the yield stress of these materials as a rheological parameter example. We have shown that it is more appropriate to control the water distribution in order to control the rheological properties of theses suspensions by taking into account the spongy nature of the lignocellulosic material. We have shown how to determine the critical concentrations separating the semi-concentrated, concentrated, triphasic and the wet granular behaviors and their relationship with yield stress. In the fourth chapter, we studied the effect of changes in the anaerobic digestion operating parameters, such as fiber size, temperature and TS on the rheological properties of materials. Several models and empirical equations have been proposed to quantify the advantage of making changes in the operating parameters on the rheology of these materials
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Shaikh, Saif. "Dynamics and rheology of concentrated suspensions of rigid fibers." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0495.
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Une étude combinant expériences et analyses est menée afin de rationaliser la dynamique et la rhéologie des suspensions très concentrées de fibres rigides, non colloïdales dans un fluide newtonien. Des mesures rhéologiques couplées à des mesures de la microstructure sont réalisées à l’aide de plusieurs dispositifs expérimentaux permettant d’analyser différents types de géométries et d’écoulements. Des expériences de rhéologie standards (rhéologie à volume contrôlé), ainsi qu’une méthode de rhéologie non-conventionnelle (rhéologie à pression contrôlée) sont associées afin de mesurer la contrainte de cisaillement, la pression de la phase particulaire et la fraction volumique des suspensions très concentrées. Un autre dispositif expérimental a été conçu dans le but d’étudier la microstructure (distribution spatiale et distribution d’orientations) d’une suspension de fibres rigides dans un écoulement de Poiseuille oscillant. Alors que ce type d’écoulement est réversible pour un liquide newtonien, dans le cas d’une suspension concentrée, les interactions entre particules introduisent des changements irréversibles de microstructure. Cette microstructure est affectée et a un effet sur l’écoulement imposé, cette dépendance non-linéaire incluant les interactions hydrodynamiques. L’objectif de ces expériences est d’apporter un éclairage sur des effets tels que la rhéofluidification observée à fort taux de cisaillement et sur le démixage dû à la migration induite par cisaillement<br>A combined work of experiments and data analyses is proposed to investigate the dynamics and rheology of highly concentrated suspensions of non-colloidal rigid rods in a Newtonian fluid. Detailed measurements of the rheology and the microstructure are made using a variety of experimental devices with different geometries and imposed flows. Standard rheology experiments (volume-controlled rheology), as well as a novel method of rheometry, are carried out to measure torques, particle pressures, and volume fractions at high concentration (pressure-controlled rheology). Another experiment has been designed and constructed to study the microstructure (spatial and orientation distribution) of a suspension of rigid rods in an oscillatory parabolic flow. Though the flow is reversible in these systems, the changes in the microstructure are irreversibile in the case of concentrated suspensions due to particle interactions. The microstructure is affected by, and has an effect, on the imposed flows; this non-linear dependency includes hydrodynamic interactions. The purpose of these experiments is to gain insight into phenomena such as apparent shear-thinning at high shear rates and demixing due to shear-induced migration
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Fällman, Monika Carina. "Turbulence measurements in fiber suspension flows : experimental methods and results." Stockholm : Skolan för teknikvetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11460.
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Çobi, Alban C. (Alban Chris). "Design of a carbon fiber suspension system for FSAE applications." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74433.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 35).<br>Reducing weight while maintaining structural integrity is one of the key challenges Formula SAE teams face as they try and design the suspension of the formula car. The purpose of this paper is to present experimental data on designing and optimizing a carbon fiber suspension system for formula cars. The reason carbon fiber suspensions are favored over the current steel suspensions is because of they can reduce the weight of the suspension by 50%. Pull tests on an Instron machine were performed on over 15 specimens composed of a carbon fiber tube with an aluminum insert bonded to each end. Loctite E-120HP epoxy was used and the surface preparation, bond gap, and bond length were varied to find the optimal bond strength. An average bond strength of 2,382.6 pounds per square inch was determined for specimens with surface preparation. Furthermore a bond gap of 0.0065 to 0.008 inches was found to give the strongest bond.<br>by Alban C. Cobi.<br>S.B.
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Aitomäki, Yvonne. "Towards a measurement of paper pulp quality : ultrasonic spectroscopy of fibre suspensions." Licentiate thesis, Luleå tekniska universitet, EISLAB, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18216.
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For the paper and pulp industry in Sweden and Finland to remain competitive against countries with lower overheads, they have to constantly strive to improve the quality and the efficiency of the manufacturing processes. One of the ways of doing this is to introduce sensors that will provide valuable online feedback on the characteristics of the pulp so that adjustments can be made to optimise the manufacturing process. The measurement method proposed in this thesis is based on ultrasound, since it is rapid, inexpensive, non-destructive and non-intrusive. Thus could be done online. Since ultrasound propagation and attenuation depends on the material properties through which is propagates, it has the potential to provide measurements of material properties such as pulp fibre density and elasticity. The aim of this thesis is to investigate the possibility of using ultrasound to measure pulp fibre material properties. The idea is to solve the inverse problem of estimating these properties from attenuation measurements and to establish the degree of accuracy to which this can be done. Firstly a model is developed and is tested with synthetic fibres to establish is validity. It is then used to solve the inverse problem of estimating material properties from attenuation measurements, again with synthetic fibres, to test the accuracy to which these properties can be estimated. Resonance peaks in the frequency response of the attenuation were found. On closer investigation it was established that the location of these peaks in the frequency domain is sensitive to the diameter of the fibres and their material properties. If the diameter is known, these peaks improve the accuracy of the estimation process. The results of the estimation process for synthetic fibre suspensions show values for the shear modulus are within known ranges but the estimation of Poisson's ratio and Young's modulus is poor. Improving the model or the estimation procedure may lead to better results. For the method as it is to have application in the paper and pulp industry there are certain conditions that need to be fulfilled. These are that we find peaks in the frequency response of the attenuation in pulp, know the diameter distribution of the fibres and the hollow nature of the fibres does not significantly alter the results. We can then, potentially, be able to establish the shear modulus of the pulp fibres. If the shear modulus is a factor in paper quality, we may be close to an online measurement of paper pulp quality using ultrasonic spectroscopy. Improving the model may allow us to estimate further properties and take into account the fibres being hollow. The thesis consists of two parts. The first part includes an overview of the pulp and paper industry and current testing methods, background theory on which the model is based and an overview of the model that is used in predicting ultrasound attenuation. There then follows a summary of the work done, some addition points are raised in the discussion before drawing conclusions. Finally we discuss what needs to be done to take this further. The second part contains a collection of four papers describing the research.<br><p>Godkänd; 2006; 20061115 (ysko)</p>
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Aitomäki, Yvonne. "Towards a measurement of paper pulp quality : ultrasonic spectroscopy of fibre suspensions /." Luleå : Luleå tekniska universitet/Systemteknik/EISLAB, 2006. http://epubl.ltu.se/1402-1757/2006/20/index.html.
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Pintossi, Marco. "Carbon fiber reinforced composite suspensions for a solar vehicle." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20564/.
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Questa tesi si svolge nell’ambito di progettazione CAD e produzione di componenti per il settore dell’automotive in CFRP, in questo particolare caso, per un’auto elettrica a pannelli solari.
Il lavoro da me svolto, aperto con una panoramica generale sulle tecnologie a basse emissioni oggi disponibili, è stato fatto a seguito di un percorso personale divisibile in tre fasi principali iniziate nel 2018 con la collaborazione alla costruzione della vettura Emilia 4, con la quale l’Università ha preso parte all’ASC 2018, una gara tenutasi in America, che ci ha visti vincitori della categoria cruiser. Ed è proprio parlando di competizioni che entriamo nella seconda fase del mio percorso, che vede affiancarsi alla trasferta americana, la trasferta australiana del 2019 per competere nel BWSC.
La terza ed ultima fase di questo percorso, che temporalmente è avvenuta tra le due competizioni, è stata la progettazione di un componente di Emilia 4, i bracci delle sospensioni anteriori e posteriori, utilizzando la fibra di carbonio tramite la progettazione CAD 3D, sfruttando Ansys e Solidworks. Il lavoro di tesi si impegna quindi ad unire le competenze acquisite in aula con le nuove tecnologie nel campo dei materiali, usando come veicolo di comunicazione la programmazione CAD.
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Modgi, Shivamurthy. "Interaction of fibres and additives in mechanical pulp suspensions." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31434.
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Precipitated calcium carbonate (PCC) is used in the production of high value communication papers from thermo-mechanical pulp (TMP) suspensions to improve optical properties like opacity and brightness. Addition of PCC also reduces the cost of papermaking. However, the increasing use of PCC in producing high value communication papers from bleached TMP has resulted in the requirement for using cationic starch as a strength enhancing agent. Starch addition compensates for the strength loss due to addition of PCC. This thesis examines the interactions of TMP fibres, PCC, starch and other additives used in mechanical grade papermaking. The thesis also illustrates the use of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX) as a non-destructive technique to obtain the z-direction PCC filler distribution in paper. In TMP suspension loaded with PCC high degree of substitution (DS) tapioca starch was found to be better strength developing agent and retention aid compared to high DS potato starch. It was also found that Polyaluminum chloride (PAC) should be used as a coagulant when using potato starch and poly diallyldimethyl aluminum chloride (DADMAC) when using tapioca starch to get maximum benefits in terms of facilitating starch adsorption to the fibres. The effect of poly DADMAC and cationic polyacrylamide (CPAM) on total and fines/filler retention in the presence of starch was studied separately. It was found that the interaction of poly DADMAC and CPAM in the presence of starch does not help in total retention but the interaction is positive for fines/filler retention. Finally, drainage experiments showed that poly DADMAC and CPAM in the presence of tapioca starch increase drainage of TMP suspensions loaded with PCC. The z-direction filler distribution is important as it affects a number of paper properties. A total of seven industrial paper samples manufactured on the same paper machine (Horizontal Bel Baie-III) were used to illustrate the SEM/EDX technique to obtain the z-direction distribution of calcium. The calcium content was related to the filler content in the sheet. The technique for z-direction mineral distribution was further established by analyzing hand sheets prepared with a known amount of calcium carbonate. The method is expected to aid the efforts of papermakers to produce a sheet structure for various end uses if one establishes a relationship between z-direction filler distribution with paper machine operating parameters and additives used.<br>Applied Science, Faculty of<br>Chemical and Biological Engineering, Department of<br>Graduate
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Jalayer, Mazyar. "Energy reduction in pumping low consistency pulp fiber suspensions." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/39531.
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Liquid transport is a vital segment of the economy. Pumping systems – whether used at a pulp and paper mill to transfer pulp stock, to pump petroleum through cross country pipeline or to transport tailings from a mine processing plant to a disposal site – are often one of the largest consumers of electrical energy. This thesis studies energy reduction in pumping low consistency fibre suspensions. The methods and procedures described in this work are applicable to any process where pumps are utilized. The main focus is on centrifugal pumps, the most commonly used pump at processing plants. Two methods are developed to achieve energy reduction: redesign of the original equipment manufacturer (OEM) impeller and pump performance monitoring via thermodynamic method.
A novel methodology/process was developed for redesigning a more efficient impeller for existing pump installations. A computational fluid dynamics (CFD) process was developed for performance prediction of various impeller designs. The CFD process was validated using experimental pump loop results. Using OEM impeller geometry, design data and the redesign model, a series of eight optimal impellers were generated. The performances of these impellers were evaluated using the validated CFD process. The most efficient impeller design was selected for prototyping and experimental validation. A case study on Allis Chalmers PWO 6”x3”x14” pump showed that efficiency increase of 19.7% can be achieved with the redesign methodology.
The validity of thermodynamic method was also studied in low consistency fibre suspension service. Head and efficiency curves for a low consistency pulp and paper centrifugal pump were measured for various low consistency pulp suspensions (0.5%, 1.0%, and 1.5%). These curves were simultaneously determined using two different approaches: conventional magnetic flow meter and differential pressure measurements; and by utilizing suction and discharge static pressure and temperature data (the thermodynamic method). It is found that addition of up to 1.5% mass fraction of softwood Kraft pulp to water did not affect the accuracy of the efficiency measurement when using the thermodynamic method. The pump efficiency calculated by thermodynamic method is consistent with the “gold standard” flow-meter-based method for flow rates within 90 – 115% of BEP (±1.0% maximum discrepancy).