Rational extended thermodynamics of a rarefied polyatomic gas with molecular relaxation processes

Area of Science:

• Thermodynamics
• Fluid Dynamics
• Chemical Physics

Background:

• Rational extended thermodynamics models rarefied gases.
• Previous models did not individually account for molecular rotational and vibrational relaxation.

Purpose of the Study:

• To present a refined rational extended thermodynamics model for rarefied polyatomic gases.
• To individually incorporate molecular rotational and vibrational relaxation processes.
• To validate the theory using experimental ultrasonic wave data.

Main Methods:

• Developed a triple hierarchy moment system for balance equations.
• Employed the maximum entropy principle for system closure.
• Utilized a generalized BGK-type collision term with three production terms.
• Analyzed the rational extended thermodynamic theory with seven independent fields (ET7).

Main Results:

• The ET7 theory provides a more refined description of rarefied polyatomic gases.
• The model successfully incorporates individual molecular relaxation processes.
• The derived dispersion relation for ultrasonic waves aligns with experimental data for CO2, Cl2, and Br2.

Conclusions:

• The refined rational extended thermodynamics theory (ET7) offers improved accuracy for polyatomic gases.
• Individual treatment of molecular relaxation is crucial for accurate thermodynamic modeling.
• The ET7 model demonstrates strong predictive capability validated by experimental results.