tailieunhanh - Waves in fluids and solids Part 13

Tham khảo tài liệu 'waves in fluids and solids part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Acoustic Waves in Bubbly Soft Media 289 Fig. . Number densities of large a and small b bubbles in the bubbly silicone with optimal acoustic attenuation. Fig. . Comparison of acoustic attenuations versus frequency for the four different cases. 290 Waves in Fluids and Solids 6. Conclusions In this chapter we first consider the acoustic propagation in a finite sample of bubbly soft elastic medium and solve the wave field rigorously by incorporating all multiple scattering effects. The energy converted into shear wave is numerically proved negligible as the longitudinal wave is scattered by the bubbles. Under proper conditions the acoustic localization can be achieved in such a class of media in a range of frequency slightly above the resonance frequency. Based on the analysis of the spatial correlation characteristic of the wave field we present a method that helps to discern the phenomenon of localization in a unique manner. Then we taken into consideration the effect of viscosity of the soft medium and investigate the localization in a bubbly soft medium by inspecting the oscillation phases of the bubble. The proper analysis of the oscillation phases of bubbles is proved to be a valid approach to identify the existence of acoustic localization in such a medium in the presence of viscosity which reveals the existence of the significant phenomenon of phase transition characterized by an unusual collective behavior of the phases. For infinite sample of bubbly soft medium we present an EMM which enables the investigation of the strong nonlinearity of such a medium and accounts for the effects of weak compressibility viscosity surrounding pressure surface tension and encapsulating shells. Based on the modified equation of bubble oscillation the linear and the nonlinear wave equations are derived and solved for a simplified 1-D case. Based on the EMM which can be used to conveniently obtain the acoustic parameters of bubbly soft media with arbitrary structural .