Visual Study of the Dynamics of a Headbox Jet, 2000 Engineering Conference Proceedings

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The effect of the headbox contraction and jet speed is investigated with respect to the dynamics of the headbox jet. This is done through visualizations of the headbox flow. Streaks in the final paper sheet and jet are shown to be closely related to the contraction of the headbox. Quantification of the results is made by a wavelet transform of the visualization images of the jet flow as well as the structure of the final paper sheets.

The headbox jet is formed by a three-ply headbox, where the center layer is colored blue. This allows for the detec-tion of streaks in the jet and paper sheets. Also, in some of the visualizations the bottom layer is separately colored,which shows that fibers from the bottom layer can end up in the top layer after the headbox nozzle. The experiments show that the medium contraction seems to give the best result, in terms of minimizing the presence of streaks.