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TECHNICAL PAPERS

Fiber Orientation Control Related to Papermaking

[+] Author and Article Information
Allan Carlsson

Department of Mechanics, School of Engineering Sciences, Royal Institute of Technology, SE-100 44 Stockholm, Swedenallan@mech.kth.se

Fredrik Lundell

Department of Mechanics, School of Engineering Sciences, Royal Institute of Technology, SE-100 44 Stockholm, Sweden

L. Daniel Söderberg

 STFI-Packforsk AB, SE-114 86 Stockholm, Sweden

J. Fluids Eng 129(4), 457-465 (Aug 09, 2006) (9 pages) doi:10.1115/1.2436583 History: Received April 20, 2006; Revised August 09, 2006

The orientation of fibers suspended in a shear flow flowing over a solid wall has been studied experimentally. The possibility to control this orientation with physical surface modifications, ridges, has also been studied. The fiber suspension was driven by gravity down a slightly inclined glass plate and a charge-coupled device camera was used to capture images of the fibers in the flow. Image analysis based on the concept of steerable filters extracted the position and orientation of the fibers in the plane of the image. From these data, the velocity of the fibers was determined. When viewing the flow from the side, the velocity of the fibers at different heights was measured and found to agree with the theoretical solution for Newtonian flow down an inclined plate. Moving the camera so that the flow was filmed from below, the orientation, and velocity of fibers in the plane parallel to the solid surface was determined. The known relationship between the velocity and the wall normal position of the fibers made it possible to determine the height above the plate for each identified fiber. Far away from the wall, the fibers were aligned with the flow direction in both cases. In a region close to the smooth plate surface the fibers oriented themselves perpendicular to the flow direction. This change in orientation did not occur when the surface structure was modified with ridges.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Coordinate system

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Figure 2

Jeffery orbits for different values of the orbit constant C and re=8.17

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Figure 3

Schematic figure of the test section. All lengths are given in mm.

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Figure 4

Schematic figure illustrating the camera positions for the velocity profile measurements (P1, P2, and P3) and for the fiber orientation studies P4

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Figure 5

Schematic figure illustrating the flow situation with the camera positions P1–P3 and P4

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Figure 6

Image captured underneath of the flow for orientation studies (camera position P4)

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Figure 7

Filter used to find the orientation of the fibers

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Figure 8

Region in image where fibers can be detected

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Figure 9

Velocity profiles measured at three different position along the x axis (camera position P1–P3)

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Figure 10

Two-dimensional convergent channel

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Figure 11

Force distribution along fiber during rotation

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Figure 12

Minimum distance from the wall where fibers performing Jeffery orbits can occur for different orientations and aspect ratios of the fibers

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Figure 13

Angular distribution of fibers before particle-tracking analysis (camera position P4)

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Figure 14

Variations in concentration as a function of the distance from the wall (camera position P4)

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Figure 15

Fiber fraction as a function of β for different distances from the wall. Measurements performed on smooth surface (camera position P4)

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Figure 16

Fiber fraction as a function of β for different distances from the wall. Measurements performed on surface with ridges (camera position P4).

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