A fractal model of flow resistivity is proposed to investigate the relations of flow resistivity with some geometric parameters of fibrous porous metals such as porosity
pore diameter and tortuosity
and to obtain a theoretical guidance for the design of sound-absorption materials. First of all
a mathematical expression of the flow Q is obtained based on the theory of fractal geometry and fluid mechanics
and the expression is a function of the maximal mean diameter of pore λ
max
the fractal dimension D
T
of tortuosity and the pore area fractal dimension D
f
. Then
the fractal model of flow
resistivity is acquired in terms of the flow resistivity formula. The maximum error
the minimum error and the mean error between experimental results and calculation results from the model are 13.9%
7.6% and 10.6%
respectively
which verifies the accuracy of the model. The calculation results show that the flow resistivity decreases as the porosity Φ increases. When the porosity Φ and the tortuosity fractal dimension D
T
are fixed
the flow resistivity decreases as the pore area fractal dimension D
f
increases. However
when the porosity Φ and the pore area fractal dimension D
f
are fixed
the flow resistivity increases as the tortuosity fractal dimension D
T
increases. The relations between the flow resistivity and the geometric parameters are revealed more clearly by the fractal flow resistivity model than by the empirical model. It can be concluded that the results provide a reliable and theoretical guidance for the design of sound-absorption materials.
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