Entropy Generation as a Means of Examining Continuum Breakdown

Abstract

To quantify the validity and breakdown of the continuum equations of fluid flow, the concept of entropy generation is examined. This parameter is formulated utilizing statistical mechanics and kinetic theory to avoid the use of equilibrium assumptions. This analysis leads to expressions in terms of energy distribution functions. These results are applied to monatomic and diatomic molecules. A numerical procedure for computing these values using the Direct Simulation Monte Carlo Method (DSMC) is presented. Normal shock waves in argon and nitrogen were simulated at Mach numbers ranging from 1.2 to 10. Results are compared to Navier-Stokes predictions. The Navier-Stokes equations are shown to delay the onset of nonequilibrium and diminish the magnitude of nonequilibrium though the shock. Because of this, breakdown parameters based on continuum data will fail to capture the initial nonequilibrium and will not provide good measures of continuum breakdown. Error in flow variables is shown as a strong function of entropy generation, suggesting this parameter is a good indicator of continuum breakdown and onset when computed using kinetic approaches.

Open PDF

Document Details

Document Type
Technical Report
Publication Date
Mar 01, 2005
Accession Number
ADA436456

Entities

People

  • Christopher R. Schrock

Organizations

  • Air Force Institute of Technology

Tags

Communities of Interest

  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Air Force
  • Boltzmann Equation
  • Boundary Layer
  • Computational Fluid Dynamics
  • Computational Science
  • Computer Programs
  • Differential Equations
  • Energy Transfer
  • Exclusion Principle
  • Fluid Dynamics
  • Fluid Flow
  • Knudsen Number
  • Mechanics
  • Monte Carlo Method
  • Navier Stokes Equations
  • Physics Laboratories
  • Quantum Mechanics

Fields of Study

  • Physics

Readers

  • Computational Fluid Dynamics (CFD)
  • Fluid Dynamics.
  • Plasma Physics.