The effect of turbulent flow on fiber orientation in the converging nozzle of a headbox, 2008 PAPERCON Conference

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The details of flow and the influence of turbulence on the orientation state of suspension of fibers in the converging nozzle of a headbox have been investigated in some detail. High speed imaging and LDV techniques are used to quantify fiber orientation distribution and turbulent characteristics. A nearly homogenous, isotropic grid generated turbulent flow is introduced at the contraction inlet. Flow Reynolds number and inlet turbulent characteristics are varied in order to determine their effects on orientation distribution. Results show that rotational diffusion is highly influenced by inlet turbulent characteristics and decays exponentially with convergence ratio. A model is developed to characterize the effect of inlet turbulence and nozzle geometry on fiber orientation. This model is validated with extensive experimental results.