Evidence of Nonlinear Flow In Softwoods From Wood Permeability Measurements
Keywords:
Air permeability, hardwoods, softwoods, nonlinear flow, Reynolds numberAbstract
A series of air permeability measurements of softwoods and hardwoods was conducted with flow rates from 0.015 to 32 cm3/sec to examine nonlinear flow. The permeability of loblolly pine, Douglas-fir, and white spruce was found to decrease with flow rate. The critical Reynolds numbers obtained from the decrease in permeability and also from the increase in the applied pressure difference with flow rate, based on Tompkins' equation, were between 0.41 and 1.62. These were in good agreement with the values calculated from the length-to-radius ratio of pit openings in accordance with Siau and Petty's study of short capillaries. This indicated the presence of nonlinearity owing to kinetic energy losses at the pit openings. Nonlinear flow could not be detected for paper birch and basswood.References
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