Sound amplification in inhomogeneous flows of nonequilibrium gas

2016

Archives of Acoustics

The distribution of perturbations of pressure and velocity in a rectangular resonator is considered. A resonator contains a gas where thermodynamic processes take place, such as exothermic chemical reaction or excitation of vibrational degrees of a molecule's freedom. These processes make the gas acoustically active under some conditions. We conclude that the incident and reflected compounds of a sound beam do not interact in the leading order in the case of the periodic sound with zero mean pressure including waveforms with discontinuities. The acoustic field before and after forming of discontinuities is described. The acoustic heating or cooling in a resonator is discussed.

Section: Discussionmentioning

confidence: 99%

“…In the case of gases in which exothermic chemical reaction occurs (Bauer, Bass, 1973;Molevich, 2001),…”

Section: Examples: Gases With Excited Vibrational Degrees Of Moleculementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Standing Waves in a Rectangular Resonator Containing Acoustically Active Gases

2016

Archives of Acoustics

“…(18), (19) represent actually a certain way of application of the Helmholtz vector decomposition theorem, which enables us to decompose potential and solenoidal vector fields. The relations of specific perturbations in the ( ) space follow from Eqs.…”

Section: Determination Of Modesmentioning

confidence: 99%

Generation of the vorticity mode by sound in a vibrationally relaxing gas

Wojda

2012

Open Physics

Abstract:The procedure of derivation of a new dynamical equation governing the vorticity mode that is generated by sound, is discussed in detail. It includes instantaneous quantities and does not require averaging over sound period. The resulting equation applies to both periodic and aperiodic sound as the origin of the vorticity mode. Under certain conditions, the direction of streamlines of the vorticity mode may be inverted as compared with that in a fluid with standard attenuation. This reflects an anomalous absorption of sound, when transfer of momentum of the vorticity mode into momentum of sound occurs. The theory is illustrated by a representative example of the generation of vorticity in a vibrationally relaxing gas in the field of periodic weakly diffracting acoustic beam. PACS

“…One may expect that the magnetoacoustic heating and streaming reveal anomalous behavior in the acoustically active plasma. That happens to all acoustically active media independently on the physical reason of acoustical activity [7,11]. This study considers magnetoacoustic heating in a plasma with the generic heating-cooling function.…”

Section: Introductionmentioning

confidence: 99%

On the Nonlinear Effects of Magnetoacoustic Perturbations in Optically Thin Quasi-Isentropic Plasmas

Ratkowski

2018

Acta Phys. Pol. A

Nonlinear effects of planar magnetosound perturbations in a plasma are discussed. Plasma is non-adiabatic due to optically thin radiation and external heating. For these reasons, thermal instability of a plasma may appear which makes it acoustically active. The plasma is assumed to be initially homogeneous ideal gas with infinite electrical conductivity permeated by a straight magnetic field which is orthogonal to the trajectories of gas particles. The instantaneous dynamic equations which describe nonlinear effects of intense sound in quasi-isentropic plasma, are derived. Nonlinear interaction of periodic and aperiodic magnetoacoustic perturbations with the non-wave modes, are discussed. The conclusions concern dissipative or active behavior of magnetoacoustic perturbations which is determined by the kind of the heating-cooling function.