Simulation of fiber entanglement by modeling vorticity in water flow field

This research developed a model of the hydroentanglement process, based on the first priciples of fluid mechanics. This model proceeded from the assumption that fiber entanglement in the hydroentanglement process is proportional to the average vorticity in the fiberweb. Two-dimensional simulations of the water flow throught the fiberweb and forming surfaces were performed in the plane perpendicular to the machine direction (MD). In these two-dimensional simulations the time-dependent development of the flow field was investigated, and it was found that the vortices induced by the water jets were influenced by the jet pressure and diameter. It was shown that the maximum average vorticity in the fiberweb occurred at a water jet diameter of 0.127 mm which explains why jets of such diameter are commonly used in industry. Three-dimensional simulations were also performed to account for the realistic geometry of the computational domain. The influence of the forming surface permeability was investigated and it was shown that the fiber entanglement increased as the open area of the forming surface decreased.