流体中多孔球中的声散射研究

Study of sound scattering of porous spheres in fluid

沙子是一种形状复杂多样的材料,在建筑材料、海底沉积物等中都是以聚集的形式存在,这样聚集的大量沙子的特性难以直观了解,为了了解这些特性,可以用声学的方法,利用沙子对声波的反射、散射信号从中了解到沙子的一些信息.本文主要从理论上研究沙子对声波的散射特性,研究流体多孔介质中的声传播,我们引入了经典的Biot理论,建立了球坐标系下的多孔球散射模型,通过多孔球界面的边界条件推导出了表示材料散射特性的散射系数矩阵,接着利用球坐标系下的散射形式函数推导出了流体多孔球的背向散射谱.理论上获得了流体多孔球的散射特性公式,用数值的方法进行对其进行了计算,采用流体多孔沙的参数值得到了背向散射谱,并讨论了不同孔隙率及沙粒半径下的背向散射情况.

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 porous sphere in fluid,we proceed with numerical calculation.The backscattering spectra are calculated using the parameters of porous sand in fluid,and finally we discuss the backscattering with different porosity and radius of sand.