Determination of the Material Property Variations Across the Growth Ring of Softwood for Use in a Heterogeneous Drying Model Part 1. Capillary Pressure,Tracheid Model and Absolute Permeability

Abstract

Summary In this work, the extensive knowledge of wood gained at the Ecole Nationale du Génie Rural des Eaux et Forêts by using a combination of microscopic observation and experimental work is being used to postulate material property correlations for a macroscopic heterogeneous “Cerne” growth ring model of softwood. Mathematical tools such as image analysis and homogenisation are used to develop models that capture the effect of the density variation within the wood sample of important macroscopic physical parameters. This first part is devoted to mass transfer in wood due to Darcy's law. Capillary pressure correlations as a function of local density are deduced from image analysis. Thereafter, a tracheid model is proposed for softwood. Its shape evolves from earlywood to latewood according to anatomical observations. Liquid and gaseous permeability values are calculated from this model according to Poiseuille's flow within cells and assuming a linear flow-pressure loss relationship through the pits.