Non-Darcian Air Flow in Wood. Part 2. Nonlinear Flow

Abstract

Summary In this study, permeability measurements and flow rate-pressure-relationship analysis were carried out to determine whether non-Darcian flow due to nonlinear flow is present during air flow through red oak and red alder heartwood, and ponderosa pine and Douglas-fir sapwood. The results indicated that 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 cm3/s. At higher flow rates, the results for red oak showed that the superficial specific permeability at the mean pressure of 50kPa decreased with the increase of the flow rates, and the equation relating pressure drop and flow rate at a given mean pressure of 50 kPa involved 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 flow found in red oak heartwood at higher flow rates was probably nonlinear laminar flow due to the kinetic-energy losses occurring in the curved openings.