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Features of Nonlinear Sound Propagation in Vibrationally Excited Gases

Perelomova A., Kusmirek M.

Archives of Acoustics

2013

Vol. 38, No. 3

357--362

Weakly nonlinear sound propagation in a gas where molecular vibrational relaxation takes place is studied. New equations which govern the sound in media where the irreversible relaxation may take place are derived and discussed. Their form depends on the regime of excitation of oscillatory degrees of freedom, equilibrium (reversible) or non-equilibrium (irreversible), and on the comparative frequency of the sound in relation to the inverse time of relaxation. Additional nonlinear terms increase standard nonlinearity of the high-frequency sound in the equilibrium regime of vibrational excitation and decrease otherwise. As for the nonlinearity of the low-frequency sound, the conclusions are opposite. Appearance of a non-oscillating additional part which is a linear function of the distance from the transducer is an unusual property of nonlinear distortions of harmonic at the transducer high-frequency sound.

Sound velocity and parameter of nonlinearity in the two-component relaxing mixtures

Perelomova A.

Archives of Acoustics

2007

Vol. 32, No. 4

871--881

General formulae on small-signal sound velocity and parameter of nonlinearity B=A of a two-component relaxing mixture in the two limiting cases of very low and very high periods of sound (when the thermal equilibrium between components has enough time to establish or not) are derived. Sound parameters are expressed in the terms of partial derivatives of individual equations of state. For the two cases: the mixture of van der Waals gases and the suspension consisting of the ideal gas and tiny solid or liquid inclusions, sound velocity and parameter of nonlinearity B=A are evaluated as functions of mass concentration of one of the parts. The rst example concerns to the mixtures consisting of oxygen and helium, and the second one to the suspension of air and graphite and the water fog. General conclusions about acoustic features of the two-component mixtures under very high and low frequencies are drawn out.