有黏条件气泡声散射特性和衰减谱数值研究*

通过研究有黏条件下的气泡散射模型,数值分析水中单气泡声散射特性,进一步结合Beer-Lambert定律将其扩展到多气泡体系的声衰减预测。数值结果表明,随着谐波阶数递增,散射强度分布数值结果趋于稳定且前向散射增强。同时发现,无因次尺寸参量ka=0.1为过渡区与纯散射区的分界线,且在共振区间具有明显的吸收效应。对多气泡体系的声衰减预测也表明,ka 0.1时,该文气泡散射模型声衰减计算与经典ECAH模型结果吻合,在低浓度条件下声衰减谱随着剪切黏度的增加呈增宽趋势,且与体积浓度成正比例递增。模型预测的声衰减随粒径、声波频率、体积浓度分布数值特征能够为颗粒两相体系粒径及浓度表征提供理论依据。

Numerical investigation on acoustic scattering property and attenuation spectrum of air bubbles with viscosity

By investigating the scattering model of bubble incorporating the effect of viscosity, the scattering characteristics of a single bubble in water is analyzed numerically. And, the sound attenuation by multiple bubbles is predicted combining the law of Beer-Lambert, which depicts that with the harmonic number increasing, the distribution of scattering intensity stabilizes, and the forward scattering by a single bubble enhances correspondingly. The non-dimensional parameter ka (=0.1) is an important indicator for distinguishing the scattering and absorption, and the latter plays a dominate role in the resonance area. In addition, the attenuation of sound by multiple bubbles in water is consistent with the result of the classical ECAH model when ka is above 0.1, which yields a variation trend proportional to the changes of concentration, and the attenuation spectrum tends to broaden with the increase of shear viscosity at low concentration. The numerical characteristics of acoustic attenuation predicted by this model with particle size, frequency and concentration can provide theoretical basis for the measurement and characterization of particle size and concentration in the two-phase system.