Stress Strain

Fibre mats are highly compressible, and the fibre network stress induced by fluid flow through the porous medium has a cumulative effect, resulting in a heterogeneous porous medium. Also, permeability depends on the porosity. Therefore, in order to quantify the dewatering rate in a heterogeneous medium, a mathematical description of the concentration as a function of the fibre network stress is required.

The following relationships are available in PaperSim:

Stress-Strain

stress-strain

Comparison between two different constitutive equations for stress as a function of concentration (expressed here by the porosity). The Campbell-Ingmanson relationship assumes that there is a minimum required concentration so that the network can bear stress. For Campbell relationship the stress disappears only when there is no fibre left. The Wilder expression is time dependent, therefore not shown here.