On the Rarefied Gas Experiments

Area of Science:

• Thermodynamics
• Fluid Dynamics
• Statistical Mechanics

Background:

• Classical constitutive laws (Fourier, Navier-Stokes) have limited validity.
• Non-classical phenomena in rarefied gases are experimentally observed but lack comprehensive theoretical models.
• Understanding material parameter dependence on density and scaling properties is crucial for accurate modeling.

Purpose of the Study:

• To address the modeling challenges of rarefied gases beyond classical physics.
• To present and compare two theoretical frameworks: Rational Extended Thermodynamics and non-equilibrium thermodynamics with internal variables.
• To analyze the impact of density-dependent material parameters on modeling capabilities and scaling properties.

Main Methods:

• Detailed analysis of an experiment on sound speed in rarefied gases at high frequencies.
• Comparison of theoretical predictions from Rational Extended Thermodynamics and non-equilibrium thermodynamics.
• Investigation of mass density dependence of material parameters and scaling properties.

Main Results:

• The study evaluates two advanced thermodynamic frameworks for rarefied gas dynamics.
• Density dependence of material parameters significantly affects modeling and scaling properties.
• Rational Extended Thermodynamics and non-equilibrium thermodynamics offer alternative approaches to classical models.

Conclusions:

• Neither classical nor extended theories universally describe all non-classical phenomena.
• The choice of theory depends on specific conditions, including temperature and material structure.
• Density dependence is a critical factor in selecting and applying appropriate thermodynamic models for rarefied gases.