Journal articles: 'Fibre suspension'

1

Redlinger-Pohn, Jakob D., Melanie Mayr, Gregor Schaub, David Gruber, and Stefan Radl. "Fines mobility and distribution in streaming fibre networks: experimental evidence and numerical modeling." Cellulose 27, no. 16 (September 23, 2020): 9663–82. http://dx.doi.org/10.1007/s10570-020-03443-9.

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AbstractThe motion of flocculated fibres in a streaming suspension is governed by the balance of the network strength and hydrodynamic forces. With increasing flow rate through a channel, (1) the network initially occupying all space, (2) is then compressed to the centre, and (3) ultimately dispersed. This classical view neglects fibres-fines: we find that the distribution of these small particles differs in streaming suspensions. While it is known that fibre-fines can escape the fibre network, we find that the distribution of fibre-fines is non-homogenous in the network during compression: fibre-fines can be caged and retarded in the streaming fibre network. Hence, the amount of fibre-fines is reduced outside of a fibre network and enriched at the network’s interface. Aiming on selectively removing fibre-fines from a streaming network by suction, we identify a reduction of the fines removal rate. That documents a hindered mobility of fibre-fines when moving through the network of fibres. Additionally, we found evidence, that the mobility of fibre-fines is dependent on the fibre-fines quality, and is higher for fibrillar fines. Consequently, we suggest that the quality of fibre-fines removed from the suspension can be controlled with the flow regime in the channel. Finally, we present a phenomenological model to compute the length dependent fibre distribution in an arbitary geometry. For a fibre suspension channel flow we are able to predict a length-dependent fibre segregation near the channel’s centre. The erosion of a plug of long fibres was however underestimated by our model. Interestingly, our model with parameters fitted to streaming fibre suspension qualitatively agreed with the motion of micro-fibrillated cellulose. This gives hope that devices for handling flocculated fibre suspensions can be designed in the future with greater confidence.

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Sridang, P. Choksuchart, M. Heran, and A. Grasmick. "Influence of module configuration and hydrodynamics in water clarification by immersed membrane systems." Water Science and Technology 51, no. 6-7 (March 1, 2005): 135–42. http://dx.doi.org/10.2166/wst.2005.0631.

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Different immersed membrane systems were compared according to the module configuration. Filtering concentrated aqueous suspensions under constant permeate flux, the hydraulic performances of the systems were evaluated and compared through parameters such as critical permeate flux notion and trans-membrane pressure variation rates. Operational variables were membrane size and module fibre density, aeration inside or outside the fibre network, suspension concentration and physico-chemical conditioning. When using hollow fibres including a possible air injection inside the fibre network, results pointed out the positive role of the aeration on the fouling control. But too high a fibre density did not allow an optimal control when the aqueous suspension was very concentrated. On the other hand, when working with capillary membranes showing sufficient space between fibres, the major parameters were the transversal suspension flow circulation through the fibre network and the FeCl3 conditioning of the suspension. Experimental results show a possible working at a 0.07 m3.m2.h1 permeate flow rate under low TMP evolutions, 0.02 Pa/s, even if the filtration was operated under high concentrated suspension, 5 kgSS/m3.

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Manikantan, Harishankar, Lei Li, Saverio E. Spagnolie, and David Saintillan. "The instability of a sedimenting suspension of weakly flexible fibres." Journal of Fluid Mechanics 756 (September 9, 2014): 935–64. http://dx.doi.org/10.1017/jfm.2014.482.

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AbstractSuspensions of sedimenting slender fibres in a viscous fluid are known to be unstable to fluctuations of concentration. In this paper we develop a theory for the role of fibre flexibility in sedimenting suspensions in the asymptotic regime of weakly flexible bodies (large elasto-gravitation number). Unlike the behaviour of straight fibres, individual flexible filaments rotate as they sediment, leading to an anisotropic base state of fibre orientations in an otherwise homogeneous suspension. A mean-field theory is derived to describe the evolution of fibre concentration and orientation fields, and we explore the stability of the base state to perturbations of fibre concentration. We show that fibre flexibility affects suspension stability in two distinct and competing ways: the anisotropy of the base state renders the suspension more unstable to perturbations, while individual particle self-rotation acts to prevent clustering and stabilizes the suspension. In the presence of thermal noise, the dominant effect depends critically upon the relative scales of flexible fibre self-rotation compared to rotational Brownian motion.

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Feist, Markus, Hermann Nirschl, Jörg Wagner, Georg Hirsch, and Samuel Schabel. "Experimental Results for the Settling Behaviour of Particle-Fiber Mixtures." Physical Separation in Science and Engineering 2007 (February 11, 2007): 1–6. http://dx.doi.org/10.1155/2007/91740.

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Sedimentation of organic fibres and inorganic particles can be observed in several industrial applications. Fibres are involved not only in wastewater treatment but also in other separation applications. In the paper industry, the separation of inorganic filler and coating particles from short cellulose fibres is still a challenge in the recycling process. During that process, particles have to be removed to obtain a purified fibre suspension. These fibres can be used again to produce new paper. With the currently applied techniques, like screening and flotation, the efficiency of short fibre separation is very poor. Moreover, also separation by sedimentation fails due to similar settling velocities of heavy-small particles and the light and larger fibres. This paper concentrates on the sedimentation of organic fibres and inorganic particles in water. The investigated suspensions are made by resolving two different and specially produced papers a coated and an uncoated one, as well as the single components used for its production. We observe a different sedimentation behaviour according to the concentration of fibres and particles in the suspension and the pH-value of it. The main result is that, according to the fibre rate, the sedimentation behaviour is particle dominant or fibre dominant.

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Shankar, Vijay, Anton Lundberg, Taraka Pamidi, Lars-Olof Landström, and Örjan Johansson. "CFD Analysis of Turbulent Fibre Suspension Flow." Fluids 5, no. 4 (October 8, 2020): 175. http://dx.doi.org/10.3390/fluids5040175.

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A new model for turbulent fibre suspension flow is proposed by introducing a model for the fibre orientation distribution function (ODF). The coupling between suspended fibres and the fluid momentum is then introduced through the second and fourth order fibre orientation tensors, respectively. From the modelled ODF, a method to construct explicit expressions for the components of the orientation tensors as functions of the flow field is derived. The implementation of the method provides a fibre model that includes the anisotropic detail of the stresses introduced due to presence of the fibres, while being significantly cheaper than solving the transport of the ODF and computing the orientation tensors from numerical integration in each iteration. The model was validated and trimmed using experimental data from flow over a backwards facing step. The model was then further validated with experimental data from a turbulent fibre suspension channel flow. Simulations were also carried out using a Bingham viscoplastic fluid model for comparison. The ODF model and the Bingham model performed reasonably well for the turbulent flow areas, and the latter model showed to be slightly better given the parameter settings tested in the present study. The ODF model may have good potential, but more rigorous study is needed to fully evaluate the model.

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BUTLER, JASON E., and ERIC S. G. SHAQFEH. "Dynamic simulations of the inhomogeneous sedimentation of rigid fibres." Journal of Fluid Mechanics 468 (October 8, 2002): 205–37. http://dx.doi.org/10.1017/s0022112002001544.

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We have simulated the dynamics of suspensions of fibres sedimenting in the limit of zero Reynolds number. In these simulations, the dominant inter-particle force arises from hydrodynamic interactions between the rigid, non-Brownian fibres. The simulation algorithm uses slender-body theory to model the linear and rotational velocities of each fibre. To include far-field interactions between the fibres, the line distribution of force on each fibre is approximated by making a Legendre polynomial expansion of the disturbance velocity on the fibre, where only the first two terms of the expansion are retained in the calculation. Thus, the resulting linear force distribution can be specified completely by a centre-of-mass force, a couple, and a stresslet. Short-range interactions between particles are included using a lubrication approximation, and an infinite suspension is simulated by using periodic boundary conditions. Our numerical results confirm that the sedimentation of these non-spherical, orientable particles differs qualitatively from the sedimentation of spherical particles. The simulations demonstrate that an initially homogeneous, settling suspension develops clusters, or streamers, which are particle rich surrounded by clarified fluid. The instability which causes the heterogeneous structure arises solely from hydrodynamic interactions which couple the particle orientation and the sedimentation rate in particle clusters. Depending upon the concentration and aspect ratio, the formation of clusters of particles can enhance the sedimentation rate of the suspension to a value in excess of the maximum settling speed of an isolated particle. The suspension of fibres tends to orient with gravity during the sedimentation process. The average velocities and orientations, as well as their distributions, compare favourably with previous experimental measurements.

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HARLEN, OLIVER G., R. R. SUNDARARAJAKUMAR, and DONALD L. KOCH. "Numerical simulations of a sphere settling through a suspension of neutrally buoyant fibres." Journal of Fluid Mechanics 388 (June 10, 1999): 355–88. http://dx.doi.org/10.1017/s0022112099004929.

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The sedimentation of a small dense sphere through a suspension of neutrally buoyant fibres is investigated via a numerical simulation technique that includes both fibre–fibre contact forces and long-range hydrodynamic interactions. In situations where the diameter of the sphere is smaller than the length of the fibres, calculations that exclude the effect of contacts between fibres severely underestimate the drag force on the sphere measured in experiments. By including fibre–fibre contacts in our simulations we are to able to account for this discrepancy, and also the strong dependence of the drag on the initial orientation of the fibres. At low and moderate values of nL3, where n is the number of fibres per unit volume and L the fibre length, hydrodynamic interactions are found to be important in moderating the effect of contacts between fibres.An asymptotic solution is presented for the limit when the sphere diameter is much smaller than both the fibre length and inter-fibre spacing, but large compared to the fibre thickness. This is found to be in good agreement with the simulations.Results of calculations on sedimentation through a monolayer of fibres are also presented, as a model of a semi-concentrated suspension. Collisions between fibres are much more frequent, due to the geometric confinement.

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8

Voinov, Nikolai, Anastasiya Bogatkova, Denis Zemtsov, Aleksandr Vititnev, and Roman Marchenko. "Sedimentation of refined cellulosic pulp fines in the suspension during physical agglomeration." BioResources 17, no. 3 (May 3, 2022): 3883–905. http://dx.doi.org/10.15376/biores.17.3.3883-3905.

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A physical coagulator of fines was employed to separate suspensions comprising refined sulphate cellulose and waste paper, where no reagents were required. The physical coagulator was a porous cylinder with a rotating disk placed in its cavity. Using the MorFi Neo fibre analyser and the Hitachi SU 3500 digital microscope, a dispersed size distribution of well-developed fines in a suspension derived from softwood and hardwood pulp was obtained. The kinetics of fine sedimentation in the suspension was studied. The sedimentation rate of both individual agglomerates and a mass of them, as well as the magnitude of mass concentration in a cleared liquid, was determined. A relationship between the concentration of fines in the suspension and the structure of the pulp during their sedimentation was established. To intensify the fines sedimentation process, it was proposed to return a part of the sediment to the suspension passing into the physical coagulator. Process parameters for the sedimentation process and the construction of the sedimentation tank were obtained. The unit designed for collecting fines from the suspension is shown schematically. Use of this unit reduced the fibre sedimentation time, decreased the loads in wastewaters, and retained the consumer value of the pulp fibres.

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9

Mackaplow, Michael B., and Eric S. G. Shaqfeh. "A numerical study of the rheological properties of suspensions of rigid, non-Brownian fibres." Journal of Fluid Mechanics 329 (December 25, 1996): 155–86. http://dx.doi.org/10.1017/s0022112096008889.

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Using techniques developed in our previous publication (Mackaplow et al. 1994), we complete a comprehensive set of numerical simulations of the volume-averaged stress tensor in a suspension of rigid, non-Brownian slender fibres at zero Reynolds number. In our problem formulation, we use slender-body theory to develop a set of integral equations to describe the interfibre hydrodynamic interactions at all orders. These integral equations are solved for a large number of interacting fibres in a periodically extended box. The simulations thus developed are an accurate representation of the suspensions at concentrations up to and including the semidilute regime. Thus, large changes in the suspensions properties can be obtained. The Theological properties of suspensions with concentrations ranging from the dilute regime, through the dilute/semi-dilute transition, and into the semi-dilute regime, are surprisingly well predicted by a dilute theory that takes into account two-body interactions. The accuracy of our simulations is verified by their ability to reproduce published suspension extensional and shear viscosity data for a variety of fibre aspect ratios and orientation distributions, as well as a wide range of suspension concentrations.

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10

Schiek, Richard L., and Eric S. G. Shaqfeh. "A nonlocal theory for stress in bound, Brownian suspensions of slender, rigid fibres." Journal of Fluid Mechanics 296 (August 10, 1995): 271–324. http://dx.doi.org/10.1017/s0022112095002138.

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A nonlocal theory for stress in bound suspensions of rigid, slender fibres is developed and used to predict the rheology of dilute, rigid polymer suspensions when confined to capillaries or fine porous media. Because the theory is nonlocal, we describe transport in a fibre suspension where the velocity and concentration fields change rapidly on the fibre's characteristic length. Such rapid changes occur in a rigidly bound domain because suspended particles are sterically excluded from configurations near the boundaries. A rigorous no-flux condition resulting from the presence of solid boundaries around the suspension is included in our nonlocal stress theory and naturally gives rise to concentration gradients that scale on the length of the particle. Brownian motion of the rigid fibres is included within the nonlocal stress through a Fokker–Planck description of the fibres’ probability density function where gradients of this function are proportional to Brownian forces and torques exerted on the suspended fibres. This governing Fokker–Planck probability density equation couples the fluid flow and the nonlocal stress resulting in a nonlinear set of integral-differential equations for fluid stress, fluid velocity and fibre probability density. Using the method of averaged equations (Hinch 1977) and slender-body theory (Batchelor 1970), the system of equations is solved for a dilute suspension of rigid fibres experiencing flow and strong Brownian motion while confined to a gap of the same order in size as the fibre's intrinsic length. The full solution of this problem, as the fluid in the gap undergoes either simple shear or pressure-driven flow, is solved self-consistently yielding average fluid velocity, shear and normal stress profiles within the gap as well as the probability density function for the fibres’ position and orientation. From these results we calculate concentration profiles, effective viscosities and slip velocities and compare them to experimental data.

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11

MACKAPLOW, MICHAEL B., and ERIC S. G. SHAQFEH. "A numerical study of the sedimentation of fibre suspensions." Journal of Fluid Mechanics 376 (December 10, 1998): 149–82. http://dx.doi.org/10.1017/s0022112098002663.

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The sedimentation of fibre suspensions at low Reynolds number is studied using two different, but complementary, numerical simulation methods: (1) Monte Carlo simulations, which consider interparticle hydrodynamic interactions at all orders within the slender-body theory approximation (Mackaplow & Shaqfeh 1996), and (ii) dynamic simulations, which consider point–particle interactions and are accurate for suspension concentrations of nl3=1, where n and l are the number density and characteristic half-length of the fibres, respectively. For homogeneous, isotropic suspensions, the Monte Carlo simulations show that the hindrance of the mean sedimentation speed is linear in particle concentration up to at least nl3=7. The speed is well predicted by a new dilute theory that includes the effect of two-body interactions. Our dynamic simulations of dilute suspensions, however, show that interfibre hydrodynamic interactions cause the spatial and orientational distributions to become inhomogeneous and anisotropic. Most of the fibres migrate into narrow streamers aligned in the direction of gravity. This drives a downward convective flow within the streamers which serves to increase the mean fibre sedimentation speed. A steady-state orientation distribution develops which strongly favours fibre alignment with gravity. Although the distribution reaches a steady state, individual fibres continue to rotate in a manner that can be qualitatively described as a flipping between the two orientations aligned with gravity. The simulation results are in good agreement with published experimental data.

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12

KROCHAK, P. J., J. A. OLSON, and D. M. MARTINEZ. "Near-wall estimates of the concentration and orientation distribution of a semi-dilute rigid fibre suspension in Poiseuille flow." Journal of Fluid Mechanics 653 (April 30, 2010): 431–62. http://dx.doi.org/10.1017/s0022112010000406.

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A model is presented to predict the orientation and concentration state of a semi-dilute, rigid fibre suspension in a plane channel flow. A probability distribution function is used to describe the local orientation and concentration states of the suspension and evolves according to a Fokker–Planck equation. The fibres are free to interact with each other hydrodynamically and are modelled using the approach outlined by Folgar & Tucker (J. Reinf. Plast. Comp. vol. 3, 1984, p. 98). Near the channel walls, the no-flux boundary conditions as proposed by Schiek & Shaqfeh (J. Fluid Mech. vol. 296, 1995, p. 271) are applied on the orientation distribution function. With this approach, geometric constraints are used to couple the fibres' rotary motion with their translational motion. This eliminates physically unrealistic orientation states in the near-wall region. The concentration distribution is modelled in a similar manner to that proposed by Ma & Graham (Phys. Fluids vol. 17, 2005, art. 083103). A two-way coupling between the fibre orientation state and the momentum equations of the suspending fluid is considered. Experiments are performed to validate the numerical model by visualizing the motion of tracer fibres in an index-of-refraction matched suspension. The orientation distribution function is determined experimentally based on these observations of fibre motion and a comparison is made with the model predictions. Good agreement is shown particularly near the channel walls. The results indicate that at distances less than one-half of a fibre length from the channel walls, the model accurately predicts the available fibre orientation states and the distribution of fibres amongst these states. The model further predicts a large concentration gradient in this region that is also observed experimentally. The magnitude of the concentration gradient in the near-wall region is shown to increase with increasing fibre concentration.

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Sunny, Tom, Kim L. Pickering, and John McDonald-Wharry. "Improving the Alignment of Dynamic Sheet-Formed Mats by Changing Nozzle Geometry and Their Reinforcement of Polypropylene Matrix Composites." Journal of Composites Science 5, no. 9 (August 27, 2021): 226. http://dx.doi.org/10.3390/jcs5090226.

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The main objective of this study was to improve the orientation of fibres within the mats produced using dynamic sheet forming (DSF). DSF is used to make fibre mats by forcing a fibre suspension through a nozzle onto a rotating drum. In this research, the effect of nozzle geometry on the orientation of hemp fibres within DSF mats was investigated. The orientation of fibres within the mats produced was assessed using ImageJ (OrientationJ) and X-ray diffraction. It was found that, as the contraction ratio of the nozzle increased, the orientation of fibres within the fibre mats increased. It was also found that the composite tensile strength increased with increased fibre orientation.

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Hadraba, Hynek, Zdeněk Chlup, Daniel Drdlík, and Jaroslav Cihlář. "Microfibres Containing Laminates Prepared by EPD: Kinetics of Co-Deposition." Key Engineering Materials 654 (July 2015): 65–69. http://dx.doi.org/10.4028/www.scientific.net/kem.654.65.

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The aim of this work was preparation of alumina laminates and fibre reinforced alumina containing zirconia micro-fibres inside the inter-layer interface. Electrophoretic deposition was performed from concentrated isopropanolic suspensions stabilised by monochloracetic acid containing mixture of alumina powder and certain amount of zirconia micro-fibres. A method for in-situ monitoring of deposited amount of mixture of particles and fibres mass was applied to control deposition kinetics. Two different approaches for composite deposition were applied: pre-milling of powders mixture prior electrophoretic deposition and milling of suspension containing stabilization aid. Applying the optimised procedure the alumina laminates were prepared consisting of fibres in the interlayer boundary affected dramatically fracture response of these materials.

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Sykes, P., and J. M. Rallison. "Lubrication theory for a fibre suspension." Journal of Non-Newtonian Fluid Mechanics 71, no. 1-2 (July 1997): 109–36. http://dx.doi.org/10.1016/s0377-0257(97)00014-1.

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Sykes, P., and J. M. Rallison. "Lubrication theory for a fibre suspension." Journal of Non-Newtonian Fluid Mechanics 71, no. 1-2 (July 1997): 137–61. http://dx.doi.org/10.1016/s0377-0257(97)00015-3.

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Yan, Huawei, Tom Lindström, and Mikael Ankerfors. "Fibre length effect on fibre suspension flocculation and sheet formation." Nordic Pulp & Paper Research Journal 21, no. 1 (January 1, 2006): 30–35. http://dx.doi.org/10.3183/npprj-2006-21-01-p030-035.

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Moritz, Kirsten, and Eberhard Müller. "Electrophoretic Deposition of Ceramic Powders-Influence of Suspension and Processing Parameters." Key Engineering Materials 314 (July 2006): 51–56. http://dx.doi.org/10.4028/www.scientific.net/kem.314.51.

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The electrophoretic deposition (EPD) of AlN, Al2O3 and SiC, respectively, from ethanolic suspensions stabilised by suitable organic additives has been investigated. A main topic of this paper is the EPD in the direction of the gravitational force. Using an AlN suspension, the deposit weight depending on the experimental parameters was determined. The deposition was carried out under constant voltage or constant current conditions. Several factors influencing the effective electric field strength will be discussed. It could be shown that the conductivity of the suspension results mainly from the free ionic species. By EPD from the different suspensions, green bodies with monomodal pore size distributions were produced. The electrophoretic deposition of alumina from an ethanolic and from an aqueous suspension of the same composition led to similar results regarding the homogeneity of the particle packing in the deposits. The SiC suspension was also used for infiltrating woven carbon fibre mats by EPD in order to fabricate ceramic matrix composites.

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Ahmed, Shams Forruque. "Theoretical Model Development for Energy Motion of Dusty Turbulent Flow of Fibre Suspensions in a Rotational Frame." Complexity 2022 (April 12, 2022): 1–11. http://dx.doi.org/10.1155/2022/8705997.

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Fibre suspension has garnered considerable attention in turbulent flows that are used in many industries. Solid particles, such as dust particles, notably affect the turbulent flow field in a rotational frame. In assessing their impacts, the dusty turbulent flow for fibre suspensions needs to be studied in a frame of rotation that can be substantially applied in many industries. This study, therefore, aims to build a theoretical model for the energy motion of dusty turbulent flow of fibre suspensions in a rotational frame. The turbulence momentum equation was considered to formulate the model in presence of dusty fluid rotating flow of fibre suspensions. The newly derived equation was derived in second-order correlation tensors Fi,j, Wi,j, Gi,j, Si,j, Xi,j, Yi,j, Qi,j, and Ri,j at any two points in the flow domain, where the tensors were expressed as space, time, and distance functions. The developed model is a considerable improvement because it takes into account all of the potential influential parameters that could affect the motion of turbulent energy, such as dust particles, suspending particles (fibres), and rotating frame. However, the impact of these parameters on turbulence energy motion must be evaluated in order to assess the performance of turbulence systems utilized in a variety of industries, such as paper manufacturing. The present theoretical development will contribute to open up experimental and numerical research opportunities for the advancement of the industry, science, and technology.

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Bekem, Aylin, and Ahmet Unal. "Polyamide 12/E-glass Fabric Composite Production with Dip-coating." MATEC Web of Conferences 188 (2018): 01022. http://dx.doi.org/10.1051/matecconf/201818801022.

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In this study PA12 was reinforced with E-glass woven fabric by dip-coating. PA12 powder and ethanol suspensions were prepared with ratios at 30, 40 and 50% of powder to obtain different fibre contents. Coated fabrics were laid-up and kept in oven at 60°C to evaporate ethanol. Then it was placed in a compression mould and pressed. Obtained laminates were subjected to tensile, bending and impact tests. Fractured surfaces were observed. It was found that mechanical properties were highest when 40% PA powder used in suspension with dip-coating with additional lamination. Fibre failure and fibre pull-out were observed on fractured surfaces.

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Wicaksana, F., A. G. Fan, and V. Chen. "The relationship between critical flux and fibre movement induced by bubbling in a submerged hollow fibre system." Water Science and Technology 51, no. 6-7 (March 1, 2005): 115–22. http://dx.doi.org/10.2166/wst.2005.0629.

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Bubbling has been used to enhance various processes. In this paper we deal with the effect of bubbling on submerged hollow fibre membranes, where bubbling is applied to prevent severe membrane fouling. Previous work with submerged hollow fibres has observed that significant fibre movement can be induced by bubbling and that there is a qualitative relationship between fibre movement and filtration performance. Therefore, the aim of the present research has been to analyse the link between bubbling, fibre movement and critical flux, identified as the flux at which the transmembrane pressure (TMP) starts to rise. Tests were performed on vertical isolated fibres with a model feed of yeast suspension. The fibres were subject to steady bubbling from below. The parameters of interest were the fibre characteristics, such as tightness, diameter and length, as well as feed concentration. The results confirmed that the critical fluxes are affected by the fibre characteristics and feed concentration. Higher critical flux values can be achieved by using loose fibres, smaller diameters and longer fibres. The enhancement is partially linked to fibre movement and this is confirmed by improved performance when fibres are subject to mechanical movement in the absence of bubbling.

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Magalhães, Flávia, Eduardo Ferreira, Lidiane Bessa, Costa Dias, Adeodato Vieira, and Miria Reis. "Fabrication of kaolin hollow fibre membranes for bacteria removal." Processing and Application of Ceramics 14, no. 4 (2020): 303–13. http://dx.doi.org/10.2298/pac2004303m.

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This study examines the influence of the particle size, extrusion rate and sintering temperature on the characteristics of kaolin hollow fibre membranes. In addition, the produced membranes were applied for bacteria removal from an aqueous suspension. The milling process reduced the size of kaolin particles from 8.7 to 5.1 ?m and greatly enhanced the morphology and mechanical resistance of the produced membranes. The increase in the sintering temperature up to 1250?C caused crystallographic phase modifications in the crude kaolin, which were mainly assigned to transformations of quartz and kaolinite to mullite and cristobalite phases. The fibres sintered at 1250?C have bending strength of 145MPa, but this relatively high sintering temperature caused a substantial particle densification and drastic decrease of the membrane water permeability. The kaolin hollow fibre membranes enabled almost total removal of the Enterobacter bacteria from an aqueous suspension.

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Magalhães, Flávia, Eduardo Ferreira, Lidiane Bessa, Costa Dias, Adeodato Vieira, and Miria Reis. "Fabrication of kaolin hollow fibre membranes for bacteria removal." Processing and Application of Ceramics 14, no. 4 (2020): 303–13. http://dx.doi.org/10.2298/pac2004303m.

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This study examines the influence of the particle size, extrusion rate and sintering temperature on the characteristics of kaolin hollow fibre membranes. In addition, the produced membranes were applied for bacteria removal from an aqueous suspension. The milling process reduced the size of kaolin particles from 8.7 to 5.1 ?m and greatly enhanced the morphology and mechanical resistance of the produced membranes. The increase in the sintering temperature up to 1250?C caused crystallographic phase modifications in the crude kaolin, which were mainly assigned to transformations of quartz and kaolinite to mullite and cristobalite phases. The fibres sintered at 1250?C have bending strength of 145MPa, but this relatively high sintering temperature caused a substantial particle densification and drastic decrease of the membrane water permeability. The kaolin hollow fibre membranes enabled almost total removal of the Enterobacter bacteria from an aqueous suspension.

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Djalili-Moghaddam, Mina, and Staffan Toll. "Fibre suspension rheology: effect of concentration, aspect ratio and fibre size." Rheologica Acta 45, no. 3 (September 30, 2005): 315–20. http://dx.doi.org/10.1007/s00397-005-0021-y.

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Jian-Zhong, Lin, Li Jun, and Zhang Wei-Feng. "Orientation distribution of fibres in a channel flow of fibre suspension." Chinese Physics 14, no. 12 (November 30, 2005): 2529–38. http://dx.doi.org/10.1088/1009-1963/14/12/026.

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Wong, Shiu-chun. "The fibre of the iterated Freudenthal suspension." Mathematische Zeitschrift 215, no. 1 (January 1994): 377–414. http://dx.doi.org/10.1007/bf02571721.

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Reddy, B. D., and G. P. Mitchell. "Finite element analysis of fibre suspension flows." Computer Methods in Applied Mechanics and Engineering 190, no. 18-19 (January 2001): 2349–67. http://dx.doi.org/10.1016/s0045-7825(00)00238-3.

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Hamedi, Naser, and Lars-Göran Westerberg. "Simulation of Flexible Fibre Particle Interaction with a Single Cylinder." Processes 9, no. 2 (January 20, 2021): 191. http://dx.doi.org/10.3390/pr9020191.

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In the present study, the flow of a fibre suspension in a channel containing a cylinder was numerically studied for a very low Reynolds number. Further, the model was validated against previous studies by observing the flexible fibres in the shear flow. The model was employed to simulate the rigid, semi-flexible, and fully flexible fibre particle in the flow past a single cylinder. Two different fibre lengths with various flexibilities were applied in the simulations, while the initial orientation angle to the flow direction was changed between 45° ≤ θ ≤ 75°. It was shown that the influence of the fibre orientation was more significant for the larger orientation angle. The results highlighted the influence of several factors affecting the fibre particle in the flow past the cylinder.

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Kondora, Grzegorz, and Dariusz Asendrych. "Modelling the Dynamics of Flexible and Rigid Fibres." Chemical and Process Engineering 34, no. 1 (March 1, 2013): 87–100. http://dx.doi.org/10.2478/cpe-2013-0008.

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Abstract A particle-level simulation technique has been developed for modelling fibre suspension flow in a converging channel of a papermachine headbox. The fibre model is represented by a chain of elements connected together. The model was verified by the simulation of rigid fibre dynamics in a simple shear flow. The period of rotation was found to be in a very good agreement with theory and reference data. The model was then employed to simulate fibre motion in a converging channel of a papermachine headbox. Fibre suspension motion was resolved using two-step procedure. Velocity field was calculated by means of a commercial CFD code ANSYS Fluent with RSM turbulence model applied and used as an input to the in-house code allowing to simulate fibre dynamics. Results of the calculations were used to construct the fibre orientation probability distribution (FOPD) which was found to be consistent with available experimental data.

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30

Schiek, Richard L., and Eric S. G. Shaqfeh. "Cross-streamline migration of slender Brownian fibres in plane Poiseuille flow." Journal of Fluid Mechanics 332 (February 1997): 23–39. http://dx.doi.org/10.1017/s0022112096003291.

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We consider fibre migration across streamlines in a suspension under plane Poiseuille flow. The flow investigated lies between two infinite, parallel plates separated by a distance comparable to the length of a suspended fibre. We consider the weak flow limit such that Brownian motion strongly affects the fibre position and orientation. Under these conditions, the fibre distribution, fibre mobility and fluid velocity field all vary on scales comparable to the fibre's length thus complicating a traditional volumeaveraging approach to solving this problem. Therefore, we use a non-local derivation of the stress. The resulting fully coupled problem for the fluid velocity, fibre stress contribution and fibre distribution function is solved self-consistently in the limit of strong Brownian motion. When calculated in this manner, we show that at steady state the fibres’ centre-of-mass distribution function shows a net migration of fibres away from the centre of the channel and towards the channel walls. The fibre migration occurs for all gap widths (0 ≤ λ ≤ 35) and fibre concentrations (0 ≤ c ≤ 1.0) investigated. Additionally, the fibre concentration reaches a maximum value around one fibre half-length from the channel walls. However, we find that the net fibre migration is a relatively small change over the fibre's uniform bulk distribution, and typically the centre-of-mass migration changes the uniform concentration profile by only a few percent.

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Harlen, O. G., and Donald L. Koch. "Simple shear flow of a suspension of fibres in a dilute polymer solution at high Deborah number." Journal of Fluid Mechanics 252 (July 1993): 187–207. http://dx.doi.org/10.1017/s0022112093003726.

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The behaviour of fibre suspensions in dilute polymer solutions at high Deborah numbers is analysed. In particular, we calculate the change to the extension of the polymers and the orientation of the fibres caused by hydrodynamic interactions between the polymers and the fibres. At a sufficiently high Deborah number the combined effect of the fibre velocity disturbances and the mean shear flow produce a dramatic increase in the extension of the polymers, similar to the coil-stretch transition observed in extensional flow.The non-Newtonian stresses caused by the polymers produce a perturbation to the angular velocity of the fibres, giving rise to a net drift across Jeffery orbits towards the vorticity axis. Unlike the second-order-fluid analysis of Leal (1975), this effect does not depend on the second-normal-stress difference.

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32

Pozegic, Thomas R., Samantha Huntley, Marco L. Longana, Suihua He, R. M. Indrachapa Bandara, Simon G. King, and Ian Hamerton. "Improving Dispersion of Recycled Discontinuous Carbon Fibres to Increase Fibre Throughput in the HiPerDiF Process." Materials 13, no. 7 (March 27, 2020): 1544. http://dx.doi.org/10.3390/ma13071544.

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In order to increase the material throughput of aligned discontinuous fibre composites using technologies such as HiPerDiF, stability of the carbon fibres in an aqueous solution needs to be achieved. Subsequently, a range of surfactants, typically employed to disperse carbon-based materials, have been assessed to determine the most appropriate for use in this regard. The optimum stability of the discontinuous fibres was observed when using the anionic surfactant, sodium dodecylbenzene sulphonate, which was superior to a range of other non-ionic and anionic surfactants, and single-fibre fragmentation demonstrated that the employment of sodium dodecylbenzene sulphonate did not affect the interfacial adhesion between fibres. Rheometry was used to complement the study, to understand the potential mechanisms of the improved stability of discontinuous fibres in aqueous suspension, and it led to the understanding that the increased viscosity was a significant factor. For the shear rates employed, fibre deformation was neither expected nor observed.

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Yang, Zhi Yuan, Hai Zhen Shi, and Yan Jun Tang. "Changes in Layer Properties and Physical Properties of Papers from Old Corrugated Container Fibres with PDADMAC/HEC Polyelectrolyte Multilayers." Advanced Materials Research 496 (March 2012): 67–70. http://dx.doi.org/10.4028/www.scientific.net/amr.496.67.

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In this paper, Old Corrugated Container (OCC) was used as the raw material for making paper. The layer-by-layer (LBL) assembly process of creating highly structured thin films was adopted to modify the surface of OCC fibres. Poly dimethyldiallylammonium chloride (PDADMAC) and hydroxyethyl cellulose (HEC) have been used to build up polyelectrolyte multilayers on OCC fibres under a certain condition. Zeta potential analyzer was used to monitor the dynamic adsorption of PDADMAC and HEC with different amount on OCC fibers. Strength measurements of the sheets including tensile index and bursting index were also determined, showing a significant improvement in physical strength with the increase of adsorbed layer number. Compared with not being processed sheets, tensile index and bursting index of sheets from treated fibre with polyelectrolyte multilayers were raised by 36.65% and 49.50%, respectively. Furthermore, filtration time analysis of OCC fibre suspension showed that the built up of PDADMAC and HEC on OCC fibres could improve the fiber-fiber joint strength of joints from polymer-treated fibers, which made the filtration time decline from 30 s to 10.6 s. In addition, SEM was introduced to observe the morphology of the PDADMAC/HEC multilayers. The images revealed that the surface of OCC fibres structured a film like plastic, which could be ascribed to the adsorption layer of polyelectrolyte.

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Papilin, N. M., A. F. Kapitanov, V. A. Volkov, A. Yu Gladyshev, V. G. Babashov, and N. M. Varrik. "Basis for the formula for the fibre suspension." Fibre Chemistry 41, no. 5 (September 2009): 314–16. http://dx.doi.org/10.1007/s10692-010-9195-x.

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35

Yenjaichon, Wisarn, John R. Grace, C. Jim Lim, and Chad P. J. Bennington. "Gas dispersion in horizontal pulp-fibre-suspension flow." International Journal of Multiphase Flow 49 (March 2013): 49–57. http://dx.doi.org/10.1016/j.ijmultiphaseflow.2012.10.001.

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36

Hämäläinen, J., S. B. Lindström, T. Hämäläinen, and H. Niskanen. "Papermaking fibre-suspension flow simulations at multiple scales." Journal of Engineering Mathematics 71, no. 1 (November 16, 2010): 55–79. http://dx.doi.org/10.1007/s10665-010-9433-5.

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37

McComb, W. D., and K. T. J. Chan. "Laser-Doppler anemometer measurements of turbulent structure in drag-reducing fibre suspensions." Journal of Fluid Mechanics 152 (March 1985): 455–78. http://dx.doi.org/10.1017/s0022112085000787.

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A laser-Doppler anemometer (LDA) was used to measure turbulent velocities in drag-reducing fibre suspensions. Measurements of streamwise velocities (and, in one case, the circumferential velocity as well) were made in flow through a straight pipe at x/d = 190, and at Reynolds numbers in the range 1.4 × 104–5.3 × 104. The fibres used were chrysotile asbestos of high aspect ratio (∼ 106), at a concentration of 300 w.p.p.m. They were dispersed in an aqueous solution of a surfactant (0.5% by weight Aerosol OT). In some experiments, the fibre suspensions were supplemented by a drag-reducing polymer (Separan AP30) at a concentration of 150 w.p.p.m. A complete experiment involved passing a quantity of fibre suspension through the apparatus a number of times (at a given Reynolds number) and measuring the velocity distribution across the pipe during each pass. As the amount of drag reduction generally declined with the number of passes (i.e. due to fibre degradation), this provided a convenient way of varying the percentage drag reduction as an experimental parameter. Results were obtained for mean velocity and intensity profiles, autocorrelations, and one-dimensional energy spectra. The mean period of turbulent bursts was determined by measuring autocorrelations with short sampling times.At the lowest Reynolds number (Re = 1.4 × 104), drag reductions of about 70% were obtained during the first two passes. This was accompanied by a reduction in the streamwise intensity below the level obtained in the surfactant solution alone. (Note: The opposite behaviour is found in drag-reducing polymer solutions, where intensity levels are larger than those in the solvent alone.) A measurement of the r.m.s. circumferential velocity showed an increased level (relative to surfactant alone) during this part of the experiment. During further passes, there was a transition to ‘polymer-like’ behaviour, with increased streamwise intensity, which subsequently declined with pass number (and hence drag reduction) towards the result for surfactant alone. This effect had previously been found in preliminary experiments at Re = 9 × 103 (McComb & Chan 1979). Repetition of the experiment a Re = 1.4 × 104, with the addition of Separan AP30, confirmed the existence of this transition from ‘fibre-like’ to ‘polymer-like’ drag reduction. In this case, the drag reduction was smaller (at about 60%), but the mixed suspension was much more resistant to degradation, with transition occurring at the ninth pass. However, such behaviour was not found at higher Reynolds numbers (Re = 3.2 × 104 and 5.3 × 104), in fibre suspensions where increased streamwise intensities occurred, even at high levels of drag reduction (about 70%).Anomalous streamwise autocorrelations were found during ‘fibre-like’ drag reduction but in the ‘polymer-like’ regime they were very similar to those measured in polymer solution, and showed characteristically increased lengthscales. On the other hand, energy spectra were found to be anomalous in all cases and showed an energy deficit at lengthscales of the same order as the fibre length. Finally, mean bursting periods were found to be much increased, with the increases being about the same as those in polymer solutions at the same Reynolds number and percentage drag reduction.

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Eberling-Fux, N., R. Pailler, A. Guette, Sebastien Bertrand, and Eric Philippe. "Impregnation of 3D Woven Carbon Fibre Preforms by Electrophoretic Deposition of Single and Mix of Non Oxide Ceramic Nanoscale Powders, and Densification of the Composite Material." Advances in Science and Technology 50 (October 2006): 91–96. http://dx.doi.org/10.4028/www.scientific.net/ast.50.91.

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3D woven carbon fibre preforms (~ 2 mm thickness) were impregnated with single or mixture of non oxide ceramic nanoscale powders in ethanolic suspensions using electrophoretic deposition (EPD). The measurement of the ζ potential of the suspension compared with its behaviour in sedimentation permits to conclude about the optimal concentration of surfactant necessary to get the most stable suspension. The experimental results were in agreement with the theoretical ones obtained using DLVO (Derjaguin, Landau, Verwey and Overbeek) theory. EPDs were carried out by applying a constant voltage between the 3D carbon fibre preform serving as deposition electrode and counter electrodes in graphite. The effect of the powder concentration on the rate and the quality of impregnation was studied. A qualitative model based on the experimental results and literature was then proposed. Experiments were not only carried out on raw 3D fibrous preforms but also on preforms with interphases. SEM and optical micrographies of fractured and polished sections of the infiltrated fabrics revealed that a quite high degree of infiltration (rates of impregnation estimated between 50 and 70 %) was obtained. At last, the composite was densified using spark plasma sintering (SPS).

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39

AZAIEZ, J. "Linear stability of free shear flows of fibre suspensions." Journal of Fluid Mechanics 404 (February 10, 2000): 179–209. http://dx.doi.org/10.1017/s002211209900717x.

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A linear stability analysis of the mixing layer in the presence of fibre additives is presented. Using a formulation based on moments of the probability distribution function to determine the particle orientation, we extend the classical linear stability theory and derive a modified Orr–Sommerfeld equation. It is found that, for large Reynolds numbers, the flow instability is governed by two parameters: a dimensionless group H, analogous to a reciprocal Reynolds number representing the importance of inertial forces versus viscous forces associated with the anisotropic elongational viscosity of the suspension; and a coefficient CI that accounts for inter-particle hydrodynamic interactions. A parametric study reveals that both parameters can induce an important attenuation of the flow instability. Furthermore, we show that the stabilizing effects arise from the orientation diffusion due to hydrodynamic interactions, and not from the anisotropy induced by the presence of fibres in the flow, as speculated before. The examination of profile contours of different perturbation terms and the analysis of the rate of production of enstrophy show clearly that the main factor behind the reduction of the flow instability is associated with the fibre shear stress disturbance. This disturbance acts as a dissipative term as the fibres, due to the orientational diffusivity arising from hydrodynamic interactions, deviate from the fully aligned anisotropic orientation. On the other hand, fibre normal stresses act as a destabilizing factor and are important only in the absence of hydrodynamic interactions.

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Kamiyama, Yasuhiko. "Geometric Approximation Of The Fibre Of The Freudenthal Suspension." Bulletin of the London Mathematical Society 30, no. 6 (November 1998): 635–42. http://dx.doi.org/10.1112/s0024609398004603.

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41

Munganga, J. M. W., B. D. Reddy, and K. J. Diatezua. "Aspects of the thermodynamic stability of fibre suspension flows." Journal of Non-Newtonian Fluid Mechanics 92, no. 2-3 (August 2000): 135–50. http://dx.doi.org/10.1016/s0377-0257(00)00092-6.

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42

Fan, X. J., N. Phan-Thien, and R. Zheng. "Simulation of fibre suspension flow with shear-induced migration." Journal of Non-Newtonian Fluid Mechanics 90, no. 1 (April 2000): 47–63. http://dx.doi.org/10.1016/s0377-0257(99)00054-3.

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43

Cui, Heping, and John R. Grace. "Flow of pulp fibre suspension and slurries: A review." International Journal of Multiphase Flow 33, no. 9 (September 2007): 921–34. http://dx.doi.org/10.1016/j.ijmultiphaseflow.2007.03.004.

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44

Pettersson, Johan, and Anders Rasmuson. "LDA Measurements on a Turbulent Gas/Liquid/Fibre Suspension." Canadian Journal of Chemical Engineering 82, no. 2 (May 19, 2008): 265–74. http://dx.doi.org/10.1002/cjce.5450820208.

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45

Jiang, Guozhan, Thomas A. Turner, and Stephen J. Pickering. "The shear viscosity of carbon fibre suspension and its application for fibre length measurement." Rheologica Acta 55, no. 1 (November 23, 2015): 1–10. http://dx.doi.org/10.1007/s00397-015-0890-7.

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46

Hardacre, Allan K., Roger G. Lentle, Sia-Yen Yap, and John A. Monro. "Predicting the viscosity of digesta from the physical characteristics of particle suspensions using existing rheological models." Journal of The Royal Society Interface 15, no. 142 (May 2018): 20180092. http://dx.doi.org/10.1098/rsif.2018.0092.

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The measurement of the viscosity of digesta is complicated by settling and compositional changes that accompany digestion. The current work determined whether the apparent and relative viscosities ( η a and η r ) of digesta could be accurately determined from the actual and maximum solid volume fractions ( ϕ and ϕ max , respectively) using the Maron–Pierce equation. The rheological properties of digesta from the small intestine of six pigs were determined at a shear rate of 1 s −1 at 37°C. A series of suspensions of plant fibre in a Newtonian liquid (70% aqueous fructose) were made at viscosities similar to pig digesta by adjusting ϕ . The relationships between the apparent and relative viscosities ( η a and η r ) and the plant fibre properties; aspect ratio (AR) and ϕ and ϕ max were then determined for digesta and the suspensions. The ARs for the digesta and plant fibre particles were determined using image analysis of scanning electron micrographs and η a from rheometric flow curves at 37°C, ϕ from image analysis and gas pycnometry, and ϕ max from AR and suspension viscosity. The η r of pig digesta and the test suspensions calculated using the Maron–Pierce equation were, with the exception of two outliers, in proportion with η a determined using a rheometer, indicating that η r could be successfully predicted from the Maron–Pierce equation.

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47

Selick, Paul. "The Fibre of the Double Suspension is an H-Space." Canadian Mathematical Bulletin 28, no. 1 (March 1, 1985): 124–28. http://dx.doi.org/10.4153/cmb-1985-015-6.

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48

Faia, Pedro, Rui Silva, Maria G. Rasteiro, and Fernando Garcia. "Electrical Tomography: A Review of Configurations, and Application to Fibre Flow Suspensions Characterisation." Applied Sciences 10, no. 7 (March 30, 2020): 2355. http://dx.doi.org/10.3390/app10072355.

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Understanding the behaviour of suspension flows continues to be a subject of great interest considering its industrial relevance, regardless of the long time and effort dedicated to it by the scientific and industrial communities. Information about several flow characteristics, such as flow regimen, relative velocity between phases, and spatial distribution of the phases, are essential for the development of exact models for description of processes involving pulp suspension. Among the diverse non-invasive techniques for flow characterisation that have been reported in the literature for obtaining experimental data about suspension flow in different processes, Electrical Tomography is one of the most interesting, since it presents perhaps the best compromise among cost, portability, and, above all, safety of handling (indeed there is no need to use radiation, which requires special care when using it). In this paper, a brief review and comparison between existing technologies for pulp suspension flow monitoring will be presented, together with their strengths and weaknesses. Emphasis is given to Electrical Tomography, because it offers the above-mentioned compromise and thus was the strategy adopted by the authors to characterise different flow processes (solid–liquid, liquid–liquid, fibres, etc.). The produced portable EIT system is described, and examples of results of its use for pulp suspension flow characterisation are reported and discussed.

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Gardiner, Phillip F., Michèle Favron, and Pierre Corriveau. "Histochemical and contractile responses of rat medial gastrocnemius to 2 weeks of complete disuse." Canadian Journal of Physiology and Pharmacology 70, no. 8 (August 1, 1992): 1075–81. http://dx.doi.org/10.1139/y92-149.

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We studied the histochemical and in situ contractile changes in a rat ankle extensor, medial gastrocnemius, in which activation of muscle fibres by motoneurones was blocked for 14 days, using the sodium channel blocker tetrodotoxin applied to the sciatic nerve. Muscles were atrophied and showed slower twitch responses, greater fusion at subtetanic frequencies of stimulation, and higher twitch/tetanic ratios. Tetanic force/mm2 of fibre area and fatiguability were unchanged. Type II fibres were more atrophied and showed greater decreases in mitochondrial succinate dehydrogenase activity than type I fibres. The contractile changes resulting from complete disuse do not occur in models in which weight-bearing alone has been removed (space flight, hindlimb suspension), suggesting that the residual motoneurone activity reported in models of weightlessness is sufficient to prevent these responses. Similarly, the finding of a greater type II fibre susceptibility to complete disuse, which differs from the pattern seen in models of weightlessness, suggests that this residual motoneurone activity in the latter influences atrophic responses in a manner that is variable among motor unit types, to produce the reported preferential type I atrophy characteristic of removal of weight-bearing.Key words: disuse, atrophy, fibre types, succinate dehydrogenase, contractile properties.

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Bourden, S., R. Ben Aim, and M. Mietton-Peuchot. "Etude par capteur optique du dépôt formé lors de la filtration d'une suspension de bentonite sur fibre creuse." Revue des sciences de l'eau 6, no. 2 (April 12, 2005): 115–29. http://dx.doi.org/10.7202/705169ar.

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Lors de la filtration sur fibres creuses de suspensions de bentonite, il a été mis en évidence que le facteur limitant est la formation d'un dépôt à la surface de la fibre. Parlant de ces considérations, un dispositif optique a été mis au point pour suivre l'évolution spatio-temporelle du dépôt en cours de filtration sur fibre creuse à peau externe. Ainsi, il a pu être mis en évidence que l'influence de la vitesse d'écoulement n'est sensible qu'après un certain temps de filtration ou un certain volume filtré. Dans le domaine testé des faibles vitesses d'écoulement, il existe une période initiale où la loi de filtration sur gâteau est applicable.Dans le cas de fibres creuses à peau externe, l'optimum technique (productivité maximale) ou économique (coût minimal du m3 traité) serait donc plus à rechercher dans une optimisation de la séquence filtration-lavage que dans une augmentation de la vitesse d'écoulement. L'efficacité du réentraînement du dépôt lors du lavage peut être suivie grâce à l'équipement et au capteur développés.

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Journal articles on the topic 'Fibre suspension'

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