Mesoscopic Kinetic Approach of Nonequilibrium Effects for Shock Waves.

Area of Science:

• Fluid Dynamics
• Molecular Dynamics
• Aerospace Engineering

Background:

• Shock waves are critical in high-speed aircraft and engine development.
• Traditional Computational Fluid Dynamics (CFD) uses macroscopic variables (Mach number, pressure, density, temperature).
• Shock wave thickness is near molecular free path, making molecular motion influential.

Purpose of the Study:

• To introduce the theory and understanding of the nonequilibrium effect approach.
• To review research progress on nonequilibrium behavior in shock-related phenomena.
• To explore shock wave physics from a molecular motion level.

Main Methods:

• Solving Boltzmann-Bhatnagar-Gross-Krook (Boltzmann BGK) or Multiple Relaxation Times Boltzmann (MRT-Boltzmann) equations.
• Obtaining nonequilibrium moments of the molecular velocity distribution function.
• Analyzing the role and physical meaning of nonequilibrium moments in fluid dynamics.

Main Results:

• The nonequilibrium effect approach provides a description of shock wave characteristics distinct from macroscopic variables.
• Nonequilibrium moments influence macroscopic fluid governing equations.
• Mesoscopic kinetic approach reveals nonequilibrium behavior in shock problems like Riemann problems, shock reflection, and detonation waves.

Conclusions:

• The nonequilibrium effect approach offers a mesoscopic perspective on shock waves, differing from traditional macroscopic views.
• This approach has significant application potential for analyzing shock phenomena.
• Understanding molecular motion is key to a comprehensive understanding of shock waves.