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  • 1.
    Bergström, Roger
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Björkman, Ulf H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Basic physics of suspended fibre flow systems: I. System scales and basic thermodynamicsManuscript (Other academic)
  • 2.
    Bergström, Roger
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Björkman, Ulf H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Basic physics of suspended fibre flow systems: II. Analogy modelsManuscript (Other academic)
  • 3.
    Bergström, Roger
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Björkman, Ulf H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Material parameters of suspended wood fibre networks: I. Methods of measurementManuscript (Other academic)
  • 4.
    Bergström, Roger
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Björkman, Ulf H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Material parameters of suspended wood fibre networks: II. MeasurementsManuscript (Other academic)
  • 5.
    Bergström, Roger
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Björkman, Ulf H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Stress chains in fibre suspensions: a formation scenarioManuscript (Other academic)
  • 6.
    Bergström, Roger
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Björkman, Ulf H.
    The interaction between fibre flocs in shear flow fieldsManuscript (Other academic)
  • 7.
    Björkman, Ulf
    KTH, Superseded Departments, Pulp and Paper Technology.
    Break-up of suspended fibre networks2003In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, no 1, 32-37 p.Article in journal (Refereed)
    Abstract [en]

    Suspended fibre networks form when flowing fibre suspensions come to rest. When stresses on such a network increases, the network is broken down and the fibre suspension eventually returns to a flowing condition. Here a series of experiments are described showing that the initiation of this break-down process leads to network-free voids opening up in the direction parallel to the largest compression.

  • 8.
    Björkman, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Paper Technology.
    Floc dynamics in flowing fibre suspensions2005In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, no 2, 247-252 p.Article in journal (Refereed)
    Abstract [en]

    Fibre suspensions are ubiquitous in nature and technology. They occur in flowing form and as extended networks. Flow of fibre suspensions takes place in smaller network portions, fibre floes. Fibre networks normally form when fibre flows stop and vice versa. Traditionally, fibre suspensions are treated as systems of fibres. Here they will be treated as crowded systems of compressible floes. With a large Couette device it is shown that these floes split and fuse, shrink and swell and behave much like a particulate system composed of compressible floes suspended in a liquid, which can move in and out of the floes. The investigated average shear rate range is from zero to about 600 s(-1).

  • 9.
    Björkman, Ulf
    KTH, Superseded Departments, Pulp and Paper Technology.
    Stress generation and transmission in suspended fibre networks2003In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, no 1, 38-43 p.Article in journal (Refereed)
    Abstract [en]

    Suspended fibre networks are viewed as particulate systems of closely packed non-adherent compressible flocs suspended in an incompressible penetrating matrix. Experiments show that stress chains form upon compression because the flocs stand in the way of each other. If tensile stresses are applied, the. flocs separate without significant resistance. Network voids open up between and parallel to the stress chains. The reason is that the fibres create compressible flocs with a Poisson ratio less than 0.5.

  • 10.
    Björkman, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Paper Technology.
    The nonlinear history of fibre flow research. Part 1: Background and beginning2008In: Applied Rheology, ISSN 1430-6395, E-ISSN 1617-8106, Vol. 18, no 2Article in journal (Refereed)
    Abstract [en]

    Technical fibre flows are normally flocky, but have theoretically mainly been treated as individual fibre flows. The reason for this can only be understood in the context of historic development. In Part 1 of this historic investigation the roots of fibre flow research are traced to the beginning of the 19th century. The subsequent development is followed through its formative period in the first half of the 20th century up to about WW2. Part 2 will continue up to about 1960s when the present main tradition had been well established. In Part 2, an example of an alternative approach will also be given, and some proposals for future development presented.

  • 11.
    Björkman, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Paper Technology.
    The nonlinear history of fibre flow research. Part 2: Continuation, reflections and suggestions2008In: Applied Rheology, ISSN 1430-6395, E-ISSN 1617-8106, Vol. 18, no 3Article in journal (Refereed)
    Abstract [en]

    Technical fibre flows are normally flocky but have theoretically mainly been treated as individual fibre flows. The reason for this can only be understood through the subject's historic development. In Part 1 of this investigation the origin of fibre flow research was traced to the beginning of the 19th century, and was followed through its formative years at the first half of the 20th century up to about WWII. This second and final part takes us up to about the 1960s when the present main theoretical research tradition had been firmly established. An example of an alternative approach is given. Finally, some suggestions for future work are advanced. In Appendix methods of characterising the inner geometry of technical fibre suspensions are discussed.

  • 12.
    Björkman, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    THE NON-NEWTONIAN FLUID MECHANICS OF TECHNICAL FIBRE SUSPENSIONS: COMPRESSIVE FLOWS2009In: Applied Rheology, ISSN 1430-6395, E-ISSN 1617-8106, Vol. 19, no 4Article in journal (Refereed)
    Abstract [en]

    The flow of non-Newtonian technical fibre suspensions (paper pulps) through a number of contractions is analysed and compared. Traditionally technical fibre flows are modelled as flow of fibres in a suspending medium. Here they are treated as crowded flows of fibre flocs from which the liquid may be squeezed in and out from. Compressive flows are common in the fibre-based process industry. They can e.g. be found in the head-box of a paper machine, in extruder nozzles in polymer technology, in the stirrer zone of mixers, etc. Traditionally such flows are analysed in elongational flow terms. Here it will be demonstrated that elongational and compressive flows for technical fibres suspensions differ qualitatively. The nature of technical fibre flocs is also discussed. For historic reasons they have come to be regarded as the outcome of a flocculation process of electrostatic-colloidal and/or mechanical-entanglement type. It will be shown that such a process is unnecessary for technical fibre suspensions and that these flocs are qualitatively different, viz. frozen-developed dissipative structures of the flocky fibre flow from which they originate. It will also be demonstrated that technical fibre flocs, in contrast with flocs of the chemically flocked type, are basically non-coherent, i.e. not kept together by themselves. It is this non-coherence that makes a compressive approach fruitful, for these economically important flows. An attempt to explain the reasons behind the present state of fibre flow theory is presented. The ambition is to stop to the present inproductive tradition in technical fibre flow.

1 - 12 of 12
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