Observation and modeling of acoustic scattering from a rubber spherical shell

Abstract

Acoustic backscattering from a rubber spherical shell in water is observed to contain a delayed enhancement, demonstrated to be associated with a waveguide path along the shell. This path is somewhat analogous to that of the Lamb wave observed on metallic shells. Rubber is a unique material because of its subsonic sound speed relative to water, and because shear coupling is often small enough to be neglected in typical models, making it fluid-like. This makes rubber a material of interest for coating and cloaking underwater devices and vehicles. Both fluid and elastic rubber partial wave series models are tested, using experimentally measured longitudinal and shear speeds, attenuation, and rubber density. A finite element model for the shell is also developed. Comparison of the models and experiments highlights the importance of the waveguide path to the overall scattering. Estimates for the group and phase velocities of the lowest order propagating mode in the shell are determined through waveguide normal mode analysis and Sommerfeld-Watson theory, and are shown to give good agreement with experiments in predicting the time of arrival of the waveguide path.

Acoustic Scattering Characteristics and Geometric Parameter Prediction for Underwater Multiple Targets Arranged in a Linear Pattern

“…The locations of the brightest interference stripes in the spectra of the two configurations were extracted separately, and the peak bright spots in the frequency range with clear bright interference stripes were extracted, as shown in Figure16a, c. We found the frequencies and incident angles corresponding to different peak points. Based on the above estimation results of the radius, the target distance is estimated by substituting into Equation (7). The results are shown in Figure 16b,d…”

“…We found the frequencies and incident angles corresponding to different peak points. Based on the above estimation results of the radius, the target distance is estimated by substituting into Equation (7). The results are shown in Figure 16b,d the location of each valley point, and the estimation results were statistically analyzed for the two configurations.…”

“…To calculate scattering from underwater simple geometric targets (e.g., spheres, cylinders, flat plates, etc. ), early computational methods like Partial Wave Series (PWS) [4,5], Sommerfeld-Watson Transform (SWT) [6,7], and Resonance Scattering Theory (RST) [8,9] have been proposed and extensively employed for addressing acoustic scattering problems. Conversely, when dealing with acoustic scattering from complex targets, the widely utilized methods are the finite element method (FEM) [10] and the boundary element method (BEM) [11].…”

Metamateriais acústicos: campos internos e teoria de espalhamento

“…Ela pode ser usada em problemas que modelam bolhas, como bolhas de água em óleo (ou vice-versa), ou modelos simplificados de organelas em meios celulares. Além disso, alguns tipos de silicone emborrachados, quando imersos em água, também podem ser tratados nessa dinâmica, pois a componente de cisalhamento das ondas de som no silicone é desprezível em contraste à componente longitudinal [36,37].…”

“…Problemas envolvendo bolhas, como bolhas de água imersas em óleo [33,34], ou de óleo em água [35] são modeláveis por essa dinâmica. Além disso, certos silicones emborrachados imersos em água também são tratáveis nesse modelo [36,37], pois nesse cenário, a componente de cisalhamento das ondas acústicas no silicone é desprezível se comparada à componente longitudinal.…”