A general model of deformation and flow in wet fibre webs under compression

A number of quantitative models of wet pressing have been proposed in the l iterature but none of them take into account the observed rate dependence o f the fibre network stress. This rate dependence, which is ascribed to the flow resistance of the water in the fibre walls, should be incorporated in wet pressing models. This paper presents a hydrodynamic model of wet pressi ng that makes allowance for the rate dependence of the fibre network stress and can therefore be used to study web densification and dewatering due to pressure pulses of arbitrary shape. The predictive capability of the model has been studied with the help of data from the third press of an experime ntal paper machine. The model gives good predictions of solids content over wide ranges of machine speeds, grammages and Linear loads and its predicti ve capability is quite adequate for most engineering applications.