Abstract

New Properties of Sound Waves in Nonequilibrium Media with the Negative Second Viscosity

N.Molevich (Korolev's Samara State Aerospace University, Samara, Russia)

e-mail: molevich@mb.ssau.ru

In a wide class of nonequilibrium media (e.g. nonisothermal plasmas, chemical and optical active gases, reactors, atmospheric condensation) the second (bulk) viscosity coefficient can become negative due to positive feedback between the sound disturbance and the nonequilibrium heating [1]. The following phenomena are discussed for such media with negative viscosity: (1) The amplification of sound disturbances in uniform and also in nonuniform or nonstationary media with slowly varying parameters. Non-linear mechanisms of wave growth stabilization due to non-linear saturation and nonlinear spectrum transfer are considered with the use of the third-order perturbation theory; (2) A new dispersion characteristics, the low-frequency (equilibrium) sound speed can exceed the high-frequency (frozen) speed; (3) Linear and non-linear sound beam refraction including the self-focusing (due to self-action mechanisms in acoustically active media: the gas cooling by sound and the excitation of acoustical flow in direction opposite to sound propagation) and the anomalous reflection (with reflection coefficient R>1) on a boundary between equilibrium and nonequilibrium media; (4) New properties of parametric interactions of sound waves with thermal waves and vortices. Green function is obtained for the nonstationary three-waves parametric interactions, nonstationary and stationary increments and the time of the stationary regime establishment. [1]Molevich N.E.,Oraevskii A.N.//Sov.Phys.JETP.1988.V.67.P.504.

Section : 1