Sound scattering and radiation suppression by pressurized spherical shells

Area of Science:

• Acoustics
• Mechanical Engineering
• Fluid Dynamics

Background:

• Thin-shell models are used for sound-structure interaction but lack consistency with thick-shell theory for fluid-loaded spherical shells.
• Prestress in shells can arise from differential static pressures between internal and external fluids.
• Existing ad hoc models for fluid loading may have inaccuracies.

Purpose of the Study:

• To re-derive linearized equations of motion for fluid-loaded, thin, spherical shells from first principles.
• To identify and analyze differences in fluid-loading terms compared to previous models.
• To investigate the influence of material properties and prestress on sound suppression.

Main Methods:

• Linearized equations of motion for fluid-loaded, thin, spherical shells were derived.
• Analytic solutions were obtained for sound wave scattering and resonant vibrations.
• The model was applied to analyze passive sound suppression of encapsulated gas bubbles.

Main Results:

• Identified and analyzed discrepancies in fluid-loading terms compared to prior models.
• Derived analytic solutions for scattering and vibration problems, reducing to known cases in limits.
• Characterized the impact of shell properties and prestress on low-frequency sound radiation suppression.

Conclusions:

• The re-derived model offers a more rigorous approach to fluid-loaded spherical shell dynamics.
• Prestress and material properties significantly influence underwater sound suppression.
• Soft rubber encapsulation maintains the sound suppression of free gas bubbles.