Experimental and computational calculation of longitudinal specific air permeability in populus deltoides and populus euroamericana wood

Specific air permeability was measured in the juvenile and mature sections of two poplar species at three different vacuum pressures using an apparatus with 0.001 s precision; the values were then compared with those obtained through computational calculations based on the number and diameter of vessels in each section. Cylindrical longitudinal specimens were prepared with 17.5 mm diameter, at two lengths of 50 and 100 mm. Results showed that vacuum pressure did not affect the experimental permeability values, although at lower pressures the permeability values tended to slightly decrease. Computational calculation of permeability showed the same permeability values for the two lengths of specimens in both species, while the values obtained from experimental measurement were significantly different due to the settlement of extractives in vessel elements. Permeability values obtained by computational calculations showed compatibility with vessel lumen area and diameter properties; however, no compatibility was found with vessel frequency. Significant correlation was found between the computational and experimental permeability values only when extractive content was low, and when the number and diameter of vessel elements were within a suitable range for computational modeling. It was therefore concluded that further studies should be carried out on a variety of different wood species to establish a final and authentic model for prediction of specific permeability based on the porous structure and vessel properties.