Non-Darcian air flow in wood - Part 2. Nonlinear flow

In this study, permeability measurements and flow rate-pressure-relationshi p analysis were carried out to determine whether non-Darcian flow due to no nlinear flow is present during air flow through red oak and red alder heart wood, and ponderosa pine and Douglas-fir sapwood. The results indicated tha t there was no evidence of nonlinear flow in red alder, ponderosa pine, and Douglas-fir throughout the entire range of flow rates, and for red oak at flow rates below 19.57 cm(3)/s. At higher flow rates, the results for red o ak showed that the superficial specific permeability at the mean pressure o f 50 kPa decreased with the increase of the flow rates, and the equation re lating pressure drop and flow rate at a given mean pressure of 50 kPa invol ved both a linear and quadratic dependence, thus demonstrating the presence of nonlinear flow components in wood. The calculated Reynolds number that was in the range of 0.263 to 1.05, further suggested that the nonlinear flo w found in red oak heartwood at higher flow rates was probably nonlinear la minar flow due to the kinetic-energy losses occurring in the curved opening s.