The Study Of Wave Scattering In Porous Material.

This paper is mainly focused on the sound wave scattering in porous material. We take advantage of Biot theory to study this problem. Based on this theory, we study the wave scattering in porous-saturated sand and porous aluminum by using the sphere scattering model and cylinder scattering model respectively.Sand is a kind of complicated material with different shape and size, and it is widely used in the architectural material and it exists in the marine sediment with the clustering morphology. As the sand is always in collective form, its characteristics are hard to know directly. In order to get some properties of sand, one way is to use the acoustical method, that is, we can get some useful and relative information from the reflecting and scattering signals of sand. In this paper, we theoretically analyze the wave propagation in porous medium in fluid and the characteristics of sound scattering by sand. The classical Biot’s theory is introduced and the scattering model in spherical coordinates when acoustic wave travels through porous sphere medium is built in this paper. The scattering coefficient matrix that represents the scattering characters of the materials is obtained through the boundary conditions of the interface of the porous spherical medium; the backscattering spectra of porous sphere in fluid are derived. After we theoretically deduce formula of the scattering of the saturated porous sphere in fluid, we proceed with numerical calculation. The backscattering spectra are calculated using the parameters of porous sand in fluid, and finally the backscattering with different porosity and radius of sand.Porous aluminum is a new material, which can be wildly in military use and civilian use. We study the sound scattering of the porous aluminum by using the cylinder model. We also take the wall into consideration, where exist a obstacle near the material. We also use the numerical modeling to calculate the backscattering of porous aluminum in different conditions. As a result, we get the backscattering spectrum of the porous aluminum, and we study the influence of the distance between the material and wall which has significantly influence on the scattering, meanwhile when the wall is quiet far away from the material, it seems like not existing.