A Method for Calculation Flow Resistivity of Kapok Fiber Felt

The flow resistivity is a critical parameter for evaluating the acoustic performance of the porous materials. Accurate determination of flow resistivity is essential for predicting the characteristic impedance and propagation constants of materials. In this paper, a method is proposed to calculate the flow resistivity of kapok fiber felt, aiming to accurately assess the flow resistivity of kapok fiber felt. Based on the dual-porosity equivalent model of kapok fiber felt, it is hypothesized that the flow resistivity is divided into two components. One part from the large pores between fibers, and the other part from the hollow structures within kapok fibers and the micropores on the fiber walls. The contribution of the large pores between fibers to the flow resistivity is calculated using the Tarnow_S model. Meanwhile, the hollow pores within the kapok fibers and the micropores on the fiber walls are represented as an equivalent pore. The slip effects are considered, and experimental data are utilized to solve for the average velocity across the fiber cross-section and the total internal friction, which yields the flow resistivity for the second component. The overall flow resistivity of the kapok fiber felt is obtained by summing the flow resistance of two components. Experimental measurements of the flow resistivity of kapok fiber felt were conducted, and the calculated flow resistivity was compared with the experimental results. The comparison validated the accuracy of the proposed calculation method. This method offers a cost-effective and efficient way to evaluate the acoustic performance of kapok fiber felt.