Archives of Acoustics, 37, 1, pp. 89–96, 2012

Nonlinear Influence of Sound on the Vibrational Energy of Molecules in a Relaxing Gas

Faculty of Applied Physics and Mathematics, Gdańsk University of Technology

Dynamics of a weakly nonlinear and weakly dispersive flow of a gas where molecular vibrational
relaxation takes place is studied. Variations in the vibrational energy in the field of intense sound is
considered. These variations are caused by a nonlinear transfer of the acoustic energy into energy of
vibrational degrees of freedom in a relaxing gas. The final dynamic equation which describes this is
instantaneous, it includes a quadratic nonlinear acoustic source reflecting the nonlinear character of
interaction of high-frequency acoustic and non-acoustic motions in a gas. All types of sound, periodic or
aperiodic, may serve as an acoustic source. Some conclusions about temporal behavior of the vibrational
mode caused by periodic and aperiodic sounds are made.
Keywords: relaxing gas; non-equilibrium media; nonlinear effects of sound
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