Fractal Derivative Model for Air Permeability in Hierarchic Porous Media

Air permeability in hierarchic porous media does not obey Fick′s equation or its modification because fractal objects have well‐defined geometric properties, which are discrete and discontinuous. We propose a theoretical model dealing with, for the first time, a seemingly complex air permeability process using fractal derivative method. The fractal derivative model has been successfully applied to explain the novel air permeability phenomenon of cocoon. The theoretical analysis was in agreement with experimental results.