Abstract
AbstractAn experimental study of the dewatering of wood‐pulp fiber suspensions by uniaxial compression is presented, to rationalize their dewatering dynamics within a two‐phase framework. Twenty‐seven pulp suspensions are examined, encompassing materials with different origins, preparation methodologies, and secondary treatments. For each suspension in this library, the network permeability and compressive yield stress are calibrated at low rates of dewatering. Faster compressions are then used to verify that a solid bulk viscosity is essential to match two‐phase model predictions with experimental observations, and to parameterize its magnitude. By comparing the results with a suspension of nylon fibers, we demonstrate that none of the wood‐pulp suspensions behave like an idealized fibrous porous medium. Nevertheless, the properties of pulp fiber networks can be reconciled within a two‐phase framework, and comparisons made between different wood‐pulp suspensions and between wood‐pulp and nylon fibers, by appealing to potential microstructural origins of their macroscopic behavior.
Highlights
The dynamics of deformable porous media are central to a widerange of problems in geophysics and biology and to a great many industrial processes
By comparing the results with a suspension of nylon fibers, we demonstrate that none of the wood-pulp suspensions behave like an idealized fibrous porous medium
The properties of pulp fiber networks can be reconciled within a two-phase framework, and comparisons made between different wood-pulp suspensions and between wood-pulp and nylon fibers, by appealing to potential microstructural origins of their macroscopic behavior
Summary
The dynamics of deformable porous media are central to a widerange of problems in geophysics and biology and to a great many industrial processes. The usable stroke of the piston is approximately 60 mm, with its location with the characteristic scale p* and parameters n and q estimated by linear regression (note that the notation here is a little different to that used previously) This form combines a power-law behavior in the numerator like that traditionally adopted for pulp and other materials,[22,43] with a term in the denominator that steepens the stress law at higher solid fractions and builds in a divergence as the solid fraction gets large, similar to the Krieger–Dougherty modification of Einstein's viscosity for a suspension of spherical particles.[44] With measurements of k* and p* in hand, we confirm that the compressive yield-stress calibrations are performed quasi-statically by computing the dimensionless grouping γ in Equation (9) and verifying that γ ) 1. Based on the range of η* that gave values of F within 5% of the minimum, we report an uncertainty of approximately 20% in our estimates for η*
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