Los Alamos National Laboratory, MPA-11, Sensors & Electrochemical Devices, Acoustics & Sensors Technology Team, Los Alamos, NM, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2012 Aug;59(8):1781-90. doi: 10.1109/TUFFC.2012.2382.
This work presents the general theory of resonance scattering (GTRS) by an elastic spherical shell immersed in a nonviscous fluid and placed arbitrarily in an acoustic beam. The GTRS formulation is valid for a spherical shell of any size and material regardless of its location relative to the incident beam. It is shown here that the scattering coefficients derived for a spherical shell immersed in water and placed in an arbitrary beam equal those obtained for plane wave incidence. Numerical examples for an elastic shell placed in the field of acoustical Bessel beams of different types, namely, a zero-order Bessel beam and first-order Bessel vortex and trigonometric (nonvortex) beams are provided. The scattered pressure is expressed using a generalized partial-wave series expansion involving the beam-shape coefficients (BSCs), the scattering coefficients of the spherical shell, and the half-cone angle of the beam. The BSCs are evaluated using the numerical discrete spherical harmonics transform (DSHT). The far-field acoustic resonance scattering directivity diagrams are calculated for an albuminoidal shell immersed in water and filled with perfluoropropane gas, by subtracting an appropriate background from the total far-field form function. The properties related to the arbitrary scattering are analyzed and discussed. The results are of particular importance in acoustical scattering applications involving imaging and beam-forming for transducer design. Moreover, the GTRS method can be applied to investigate the scattering of any beam of arbitrary shape that satisfies the source-free Helmholtz equation, and the method can be readily adapted to viscoelastic spherical shells or spheres.
本文提出了任意置于声场中浸入非粘性流体的弹性球壳的共振散射（GTRS）的一般理论。GTRS 公式适用于任意大小和材料的球壳，而与相对于入射光束的位置无关。这里表明，浸入水中并置于任意光束中的球壳的散射系数等于平面波入射时获得的散射系数。提供了不同类型的声学贝塞尔光束场中弹性壳的数值示例，即零阶贝塞尔光束和一阶贝塞尔涡旋和三角函数（非涡旋）光束。散射压力使用涉及光束形状系数（BSC）、球壳散射系数和光束半锥角的广义部分波级数展开来表示。BSC 使用数值离散球谐变换（DSHT）进行评估。通过从总远场形式函数中减去适当的背景，计算出浸入水中并充满全氟丙烷气体的白蛋白壳的远场声共振散射指向性图。分析和讨论了与任意散射相关的特性。这些结果在涉及换能器设计的成像和波束形成的声学散射应用中特别重要。此外，GTRS 方法可用于研究满足无源亥姆霍兹方程的任意形状光束的散射，并且该方法可以很容易地适应粘弹性球壳或球体。
