Thermal and viscous effects on sound waves: revised classical theory.

Area of Science:

• Fluid Mechanics
• Thermodynamics
• Acoustics

Background:

• Classical fluid mechanics models like Navier-Stokes-Fourier have limitations in describing dissipative phenomena in gases.
• Linear irreversible thermodynamics (LIT) offers a framework for developing more comprehensive fluid models.
• Understanding sound propagation with dissipation is crucial for various physical and engineering applications.

Purpose of the Study:

• To apply the recently developed bi-velocity fluid mechanics model to analyze sound propagation in gases.
• To incorporate first-order thermal and viscous dissipation effects into the bi-velocity model.
• To compare the bi-velocity model's predictions with classical and molecular-based approaches, as well as experimental data.

Main Methods:

• Application of the bi-velocity model derived from linear irreversible thermodynamics principles.
• Inclusion of first-order thermal and viscous dissipation effects.
• Comparative analysis against Navier-Stokes-Fourier theory and molecularly-based sound propagation calculations.

Main Results:

• The bi-velocity model successfully predicts sound propagation in gases with thermal and viscous dissipation.
• Results from the bi-velocity model show strong agreement with molecularly-based calculations and experimental data.
• The model reveals distinct entropy and evanescent viscous modes in dissipative sound propagation.

Conclusions:

• The macroscopic bi-velocity model provides an accurate and effective framework for studying dissipative sound propagation in gases.
• The model's consistency with molecular theories and experimental findings validates its utility.
• The identified entropy and viscous modes offer deeper insights into the physics of sound dissipation.