Predicting absorption and dispersion in acoustics by direct simulation Monte Carlo: Quantum and classical models for molecular relaxation

Amanda D. Hanford, Patrick D. O'Connor, James B. Anderson, Lyle Norman Long

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

In the current study, real gas effects in the propagation of sound waves are simulated using the direct simulation Monte Carlo method for a wide range of frequencies. This particle method allows for treatment of acoustic phenomena at high Knudsen numbers, corresponding to low densities and a high ratio of the molecular mean free path to wavelength. Different methods to model the internal degrees of freedom of diatomic molecules and the exchange of translational, rotational and vibrational energies in collisions are employed in the current simulations of a diatomic gas. One of these methods is the fully classical rigid-rotor/harmonic-oscillator model for rotation and vibration. A second method takes into account the discrete quantum energy levels for vibration with the closely spaced rotational levels classically treated. This method gives a more realistic representation of the internal structure of diatomic and polyatomic molecules. Applications of these methods are investigated in diatomic nitrogen gas in order to study the propagation of sound and its attenuation and dispersion along with their dependence on temperature. With the direct simulation method, significant deviations from continuum predictions are also observed for high Knudsen number flows.

Original languageEnglish (US)
Pages (from-to)4118-4126
Number of pages9
JournalJournal of the Acoustical Society of America
Volume123
Issue number6
DOIs
StatePublished - Jun 17 2008

Fingerprint

molecular relaxation
Knudsen flow
diatomic molecules
acoustics
diatomic gases
real gases
vibration
rigid rotors
propagation
simulation
polyatomic molecules
sound waves
mean free path
harmonic oscillators
Monte Carlo method
degrees of freedom
attenuation
energy levels
continuums
deviation

All Science Journal Classification (ASJC) codes

  • Arts and Humanities (miscellaneous)
  • Acoustics and Ultrasonics

Cite this

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abstract = "In the current study, real gas effects in the propagation of sound waves are simulated using the direct simulation Monte Carlo method for a wide range of frequencies. This particle method allows for treatment of acoustic phenomena at high Knudsen numbers, corresponding to low densities and a high ratio of the molecular mean free path to wavelength. Different methods to model the internal degrees of freedom of diatomic molecules and the exchange of translational, rotational and vibrational energies in collisions are employed in the current simulations of a diatomic gas. One of these methods is the fully classical rigid-rotor/harmonic-oscillator model for rotation and vibration. A second method takes into account the discrete quantum energy levels for vibration with the closely spaced rotational levels classically treated. This method gives a more realistic representation of the internal structure of diatomic and polyatomic molecules. Applications of these methods are investigated in diatomic nitrogen gas in order to study the propagation of sound and its attenuation and dispersion along with their dependence on temperature. With the direct simulation method, significant deviations from continuum predictions are also observed for high Knudsen number flows.",
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Predicting absorption and dispersion in acoustics by direct simulation Monte Carlo : Quantum and classical models for molecular relaxation. / Hanford, Amanda D.; O'Connor, Patrick D.; Anderson, James B.; Long, Lyle Norman.

In: Journal of the Acoustical Society of America, Vol. 123, No. 6, 17.06.2008, p. 4118-4126.

Research output: Contribution to journalArticle

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