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UBC Theses and Dissertations
Fiber orientation in a headbox Zhang, Xun
Abstract
The prediction of fiber orientation is a critical parameter for papermakers who wish to control the quality of their paper products. The wet end processes, especially the headbox and the drainage stage on the forming wire, play important roles in determining the fiber orientation characteristics. The current thesis is focused on the headbox flow effect on fiber orientation. It summarizes a mathematical method, which has been developed by other researchers, for predicting the orientation of rigid fibers in dilute suspensions. This method, composed of a turbulent flow simulation model and a fiber motion model, has been applied to predict fiber motion in a headbox. To validate the method, experiments have been conducted by measuring the orientation of dyed nylon fibers moving in a pilot plexiglass headbox. Comparison of experiments and the present numerical simulations of the fiber orientation shows that the simulation method proposed can predict the trend of the statistical orientation distribution of dilute suspensions in headboxes, although there exists obvious deviations between the simulations and experiments. The fibers are seen to be more strongly oriented by the predictions than is observed in the experiments. The anisotropy of the fiber orientation in the headbox flow is caused not only by the mean flow field characteristics, but also by the turbulence characteristics, and the explicit effects of the turbulence are not yet included in the predictions. The simulation method is applied to predict fiber orientations for different headbox geometry, fiber aspect ratio and flow rate. From the prediction method, using only the mean flow effects, a larger contraction ratio is found to produce more concentrated fiber orientation in the flow direction at the exit of the headbox. The channel length, the flow velocity and the fiber aspect ratio within the range of study have little influence on the fiber orientation properties.
Item Metadata
Title |
Fiber orientation in a headbox
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2001
|
Description |
The prediction of fiber orientation is a critical parameter for papermakers who wish to
control the quality of their paper products. The wet end processes, especially the headbox
and the drainage stage on the forming wire, play important roles in determining the fiber
orientation characteristics. The current thesis is focused on the headbox flow effect on
fiber orientation. It summarizes a mathematical method, which has been developed by
other researchers, for predicting the orientation of rigid fibers in dilute suspensions. This
method, composed of a turbulent flow simulation model and a fiber motion model, has
been applied to predict fiber motion in a headbox. To validate the method, experiments
have been conducted by measuring the orientation of dyed nylon fibers moving in a pilot
plexiglass headbox. Comparison of experiments and the present numerical simulations of
the fiber orientation shows that the simulation method proposed can predict the trend of
the statistical orientation distribution of dilute suspensions in headboxes, although there
exists obvious deviations between the simulations and experiments. The fibers are seen to
be more strongly oriented by the predictions than is observed in the experiments. The
anisotropy of the fiber orientation in the headbox flow is caused not only by the mean
flow field characteristics, but also by the turbulence characteristics, and the explicit
effects of the turbulence are not yet included in the predictions. The simulation method is
applied to predict fiber orientations for different headbox geometry, fiber aspect ratio and
flow rate. From the prediction method, using only the mean flow effects, a larger
contraction ratio is found to produce more concentrated fiber orientation in the flow
direction at the exit of the headbox. The channel length, the flow velocity and the fiber
aspect ratio within the range of study have little influence on the fiber orientation
properties.
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Extent |
6377131 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-08-04
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0080963
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2001-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.