A model describing axial flow of liquids through conifer wood

Summary A mathematical model has been derived for the prediction of the resistance to viscous liquid flow generated by tracheid lumina and various parts of the bordered pit structure. The model also takes into account changes in pit geometry occurring as the pit membrane deflects when a pressure differential is applied across it. Methods for checking whether flow is truly viscous are presented.Data calculated for Pinus sylvestris suggest that the permeability of earlywood differs markedly from that of latewood; that in latewood the pit apertures contribute significantly to the total resistance to flow; and that kinetic energy corrections to the Poiseuille viscous flow equation may be of some importance at high flow rates.The authors wish to acknowledge the encouragement of Professors Matthews and Roche.