Modelling of concentrated fibre suspension pipe flow with low-Reynolds-number k-ε turbulence models: new damping function

Computational Fluid Dynamics can be applied in the pulp and paper industry to simulate the flow of pulp in the different process stages. The present study is focused on the turbulent pipe flow of concentrated Eucalyptus pulp suspensions using ANSYS FLUENT (R) CFD software. A pseudo-homogeneous strategy was applied, which assumes the non-Newtonian behaviour of the pulp defined by a functional dependence of viscosity on shear rate and consistency. Also, the existence of a water annulus at the pipe wall, surrounding the core flow, was considered. A low-Reynolds-number k-epsilon turbulence model was evaluated to describe the presence of the drag reduction effect. Furthermore, the turbulence model was modified taking into account damping functions applied successfully in literature to study power-law fluid flows and particulate flows, which, nevertheless failed to describe adequately the flow of the present complex systems. Therefore, further modifications to the damping function for the case of fibre suspensions were investigated. Pressure drop was used as a control parameter to validate the CFD model. A good correspondence between numerical and experimental data was achieved when using a modified version of the damping function for particulate flows. A good replication of in-house experimental information was obtained for the cases tested.