Drift speed: a way of measuring diffusion and tortuosity of porous materials

The drift speed for pine, birch and spruce was measured. Several effects could be distinguished by comparing the fluxes with steady state results and with the theoretical diffusion obtained with the model of Einstein. By comparing the fluxes from the three models, the length of diffusion was calculated. Drift speed measurement is shown to be a great asset when studying flow in complex porous materials.