Endre søk
RefereraExporteraLink to record
Permanent link

Direct link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
A critical evaluation of ultrasound velocity profiling aiming towards measurements in fibre suspensions
KTH, Tidigare Institutioner                               , Mekanik.
KTH, Tidigare Institutioner                               , Mekanik.
KTH, Tidigare Institutioner                               , Mekanik.
STFI-Packforsk.ORCID-id: 0000-0003-3737-0091
(engelsk)Manuskript (preprint) (Annet vitenskapelig)
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-25429OAI: oai:DiVA.org:kth-25429DiVA, id: diva2:358253
Merknad
QC 20101021Tilgjengelig fra: 2010-10-21 Laget: 2010-10-21 Sist oppdatert: 2010-10-21bibliografisk kontrollert
Inngår i avhandling
1. Fluid mechanics of fibre suspensions related to papermaking
Åpne denne publikasjonen i ny fane eller vindu >>Fluid mechanics of fibre suspensions related to papermaking
2005 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

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.

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.

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.

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.

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.

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.

sted, utgiver, år, opplag, sider
Stockholm: KTH, 2005. s. x, 42
Serie
Trita-MEK, ISSN 0348-467X ; 2005:1
Emneord
Applied mechanics, applied fluid mechanics, fibre suspensions, roll-forming, sedimentation, shear flow, Teknisk mekanik
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-100 (URN)
Disputas
2005-01-14, Kollegiesalen, Valhallavägen 79, Stockholm, 10:00
Opponent
Veileder
Merknad
QC 20101021Tilgjengelig fra: 2005-02-02 Laget: 2005-02-02 Sist oppdatert: 2010-10-21bibliografisk kontrollert

Open Access i DiVA

Fulltekst mangler i DiVA

Personposter BETA

Söderberg, L. Daniel

Søk i DiVA

Av forfatter/redaktør
Fällman, MonikaLundell, FredrikHolm, RichardSöderberg, L. Daniel
Av organisasjonen

Søk utenfor DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric

urn-nbn
Totalt: 110 treff
RefereraExporteraLink to record
Permanent link

Direct link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf