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Rotational cut-off and anharmonicity effects on thermodynamic properties of gases at high temperatures

Reddy, NM (1974) Rotational cut-off and anharmonicity effects on thermodynamic properties of gases at high temperatures. In: Aeronautical Quarterly, 25 . pp. 287-292.

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Official URL: http://adsabs.harvard.edu/abs/1974AeQ....25..287R


The exact expressions for the partition function (Q) and the coefficient of specific heat at constant volume (Cv) for a rotating-anharmonic oscillator molecule, including coupling and rotational cut-off, have been formulated and values of Q and Cv have been computed in the temperature range of 100 to 100,000 K for O2, N2 and H2 gases. The exact Q and Cv values are also compared with the corresponding rigid-rotator harmonic-oscillator (infinite rotational and vibrational levels) and rigid-rotator anharmonic-oscillator (infinite rotational levels) values. The rigid-rotator harmonic-oscillator approximation can be accepted for temperatures up to about 5000 K for O2 and N2. Beyond these temperatures the error in Cv will be significant, because of anharmonicity and rotational cut-off effects. For H2, the rigid-rotator harmonic-oscillator approximation becomes unacceptable even for temperatures as low as 2000 K.

Item Type: Journal Article
Publication: Aeronautical Quarterly
Publisher: Royal Aeronautical Soc
Additional Information: Copyright of this article belongs to Royal Aeronautical Soc.
Keywords: Harmonic oscillators;high temperature gases;molecular oscillators;molecular rotation;partitions (mathematics);thermodynamic properties;gas dynamics;reentry physics;specific heat;temperature effects.
Department/Centre: Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited: 22 Jan 2010 04:48
Last Modified: 22 Jan 2010 04:48
URI: http://eprints.iisc.ac.in/id/eprint/24279

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