On some nonlinear effects in ultrasonic fields

Area of Science:

• Fluid dynamics
• Nonlinear acoustics
• Acoustic wave propagation

Background:

• Standard nonlinear acoustics models (e.g., KZK, Burgers equations) have limitations in describing complex phenomena.
• Intense sound fields in fluids can induce significant changes in fluid properties and generate higher-order effects.
• Understanding these nonlinear effects is crucial for accurate acoustic modeling and predicting wave behavior.

Purpose of the Study:

• To theoretically investigate nonlinear effects in intense sound fields in fluids.
• To extend beyond the capabilities of standard nonlinear acoustics propagation models.
• To analyze the generation of flow, heat, and other ambient state changes in fluids due to acoustic fields.

Main Methods:

• Analysis based on fundamental equations of motion for a thermoviscous fluid.
• Derivation of model equations to capture higher-order nonlinear acoustic phenomena.
• Inclusion of fluctuations in viscosity and thermal conductivity due to the sound field.
• Consideration of nonlinear effects induced by flexural vibrations.

Main Results:

• Model equations were derived to analyze nonlinear sources for flow and heat generation.
• The study accounts for fluctuations in fluid properties (viscosity, thermal conductivity) caused by intense sound.
• Nonlinear effects induced by flexural vibrations were also investigated.
• Calculations of intensity and absorption of finite amplitude sound waves were performed.

Conclusions:

• Advanced theoretical models are necessary to capture higher-order nonlinear acoustic effects in fluids.
• Intense sound fields can significantly alter fluid states, including generating flow and heat.
• The derived models provide a framework for understanding the interplay between acoustic waves and fluid properties.