Modelling a Turbulent Dilute Fibre Suspension in a Planar  Contraction : Effect of Vane Types, Vane Position and Wall  Boundary Layer on Fibre Orientation Distribution

• A model of the effect of turbulence generating vanes and its location in a planar contraction for predicting fibre orientation distribution is proposed. Simultaneously with CFD simulations and with experimental data, the non-dimensional rotational dispersion coefficient has been determined for the extended 1D headbox model. Furthermore the behavior of turbulence generating vanes types, i.e. blunt and tapered, and the location of such has been studied. For different streamlines in the contracting channel, the one dimensional fibre orientation distribution model is solved, and the fibre orientation distribution is studied along streamlines near the vane wall and vane tip and further away. The model reveals the effect of the vane tip and the wall boundary layer on fibre orientation distribution. The boundary layer will for both in the plane of paper and in the plane of contraction wider the fibre orientation distributions, i.e the fibres will be less oriented. For the outlet profile of the contraction the fibre orientation distribution will be more effected by the blunt vane tip than the tapered vane tip. The model is validated with experimental results in literature and a good qualitatively agreement was archived.

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