Bubble oscillation and inertial cavitation in viscoelastic fluids

Area of Science:

• Acoustics
• Fluid Dynamics
• Rheology
• Biomedical Engineering

Background:

• Non-linear acoustic oscillations of gas bubbles are crucial in various physical phenomena.
• Understanding bubble dynamics in viscoelastic fluids is essential for applications like ultrasonic medical treatments.
• Previous studies often simplified fluid properties, neglecting complex viscoelastic effects.

Purpose of the Study:

• To theoretically investigate the non-linear acoustic oscillations of gas bubbles in viscoelastic fluids.
• To analyze the influence of fluid rheology, including elasticity and viscosity, on bubble behavior.
• To determine the effect of the Deborah number on inertial cavitation thresholds for biomedical applications.

Main Methods:

• Formulation of the problem using a constitutive equation of differential type with an interpolated time derivative.
• Modeling fluid elasticity, shear thinning viscosity, and extensional viscosity.
• Analysis of bubble radius evolution over time under varying acoustic pressures and Deborah numbers.

Main Results:

• Bubble oscillation amplitude increases drastically with the Deborah number.
• Chaotic behavior can emerge even at moderate external pressure amplitudes.
• Rheological properties significantly influence inertial cavitation pressure thresholds.
• Critical pressure amplitudes for inertial cavitation are reduced as the Deborah number increases.

Conclusions:

• The Deborah number is a critical parameter governing bubble oscillation amplitude and potential for chaotic dynamics.
• Viscoelastic fluid properties substantially lower the pressure required for inertial cavitation.
• Findings provide valuable insights into ultrasonic biomedical applications, suggesting enhanced cavitation at lower pressures with increased fluid viscoelasticity.