Hydrodynamic alignment of nano-fibrillated cellulose in extensional flow

Authors: Håkansson, K.H., Lundell, F., Prahl Wittberg, L., Wågberg, L., Söderberg, D.
Document Type: Conference
Pubstate: Published
Journal: 8th International Conference on Multiphase Flow (ICMF), Jeju, Korea (2013)
Year: 2013


The behaviour of elongated particles in fluid flows plays an important role in many material-manufacturing processes. The energy consumption, when producing a product, is dependent on the flow, and the properties of the end-product are highly dependent on the orientation of the elongated particles inside the product. Here, bundles of rigid cellulose chains are oriented by an extensional flow. Experiments and numerical investigations are used to quantify the degree of orientation for different extensions (accelerations). The experiments utilize polarized light to detect relative orientation. A steady laminar flow simulation is used together with the Smoluchowski equation, to obtain absolute values of the orientation. The Smoluchowski equation is solved in one dimension, and by fitting the rotational diffusion coefficient together with an initial orientation, the computations and the experiments display similar behaviour. Hence, making it possible to predict absolute orientations in this flow setup. As the extension is increased, the fibrils become more aligned in the direction of the extension. Tuning the orientation by tuning an extensional flow during the manufacturing process makes it possible to control the structure and therefore also the properties of material, online in the manufacturing process.