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Experimental and theoretical stability investigations of plane liquid jets
KTH, Superseded Departments, Mechanics.ORCID iD: 0000-0003-3737-0091
KTH, Superseded Departments, Mechanics.ORCID iD: 0000-0002-1146-3241
1998 (English)In: European journal of mechanics. B, Fluids, ISSN 0997-7546, E-ISSN 1873-7390, Vol. 17, no 5, 689-737 p.Article in journal (Refereed) Published
Abstract [en]

The present investigation has been undertaken in order to better understand the development of free, plane liquid jets. Both the development of the basic laminar flow as well as its stability have been investigated theoretically and experimentally. The velocity field and free surface location of a liquid jet emanating from a plane channel was calculated numerically and the velocity and surface relaxation lengths were determined. Calculated velocity profile distributions were in good agreement with Pitot tube measurements. Temporal linear stability calculations were performed using the calculated velocity distributions. The calculations showed five unstable modes, three sinuous and two dilatational. Four of these modes have been reported earlier and one of the sinuous modes is considered to be 'new'. The linear stability calculations include surface tension as well as viscosity in the liquid and gas. Hot wire anemometry measurements of controlled forced disturbances showed that waves in the experimental jet also were sinuous and that the amplitude distribution was in fair agreement with theoretical results. Shadowgraph visualisations showed the evolution of the waves on the surface of the jet and it was found that the waves break up downstream the nozzle. This break-up was visualized by particle visualisations, which showed that it creates strong streamwise streaks in the jet.

Place, publisher, year, edition, pages
1998. Vol. 17, no 5, 689-737 p.
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-24214ISI: 000075822100001OAI: oai:DiVA.org:kth-24214DiVA: diva2:345464
Note
QC 20100825Available from: 2010-08-25 Created: 2010-08-25 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Hydrodynamics of plane liquid jets aimed at applications in paper manufacturing
Open this publication in new window or tab >>Hydrodynamics of plane liquid jets aimed at applications in paper manufacturing
1999 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

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.

Place, publisher, year, edition, pages
Stockholm: KTH, 1999. x, 48 p.
Series
Trita-MEK, ISSN 0348-467X ; 99:10
Keyword
liquid jet, transition, break-up, stability, wavelet, free surface, waves, streamwise streaks, fibre suspension, headbox, forming, shadowgraph, hot-film
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-2839 (URN)99-3009113-0 (ISBN)
Public defence
1999-09-24, 00:00
Note
QC 20100825Available from: 2000-01-01 Created: 2000-01-01 Last updated: 2010-08-26Bibliographically approved

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Söderberg, DanielAlfredsson, Henrik

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