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Ulf Bjorkman
The non-Newtonian Fluid Mechanics of Technical Fibre Suspensions: Compressive Flows

Appl. Rheol. 19:4 (2009) 44290 (24 pages)

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 headbox 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.

Cite this publication as follows:
Bjorkman U: The non-Newtonian Fluid Mechanics of Technical Fibre Suspensions: Compressive Flows, Appl. Rheol. 19 (2009) 44290.

Ulf Bjorkman
The Nonlinear History of Fibre Flow Research: Part 2. Continuation, Reflections and Suggestion

Appl. Rheol. 18:3 (2008) 34694 (26 pages)

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.

Cite this publication as follows:
Bjorkman U: The Nonlinear History of Fibre Flow Research: Part 2. Continuation, Reflections and Suggestion, Appl. Rheol. 18 (2008) 34694.

Ulf Bjorkman
The Nonlinear History of Fibre Flow Research: Part 1. Background and Beginning

Appl. Rheol. 18:2 (2008) 23974 (11 pages)

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.

Cite this publication as follows:
Bjorkman U: The Nonlinear History of Fibre Flow Research: Part 1. Background and Beginning, Appl. Rheol. 18 (2008) 23974.


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