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N. I. Pushkina

Publications and source records attributed to N. I. Pushkina.

8 recordsLinked to original sources
arXiv2015

Discontinuities in fourth sound waves in superfluid helium

Formation of fourth-sound shock waves in narrow channels filled with superfluid helium is studied. Physical and mathematical conditions at the surface of discontinuity are established. These conditions differ somewhat from those in case of first- and second-sound waves. The velocity of discontinuity coincides with that of fourth sound. The jumps of temperature and the superfluid velocity are shown to be of the first order as to the pressure jumps.

cond-mat.other↗
arXiv2015

Acoustic wave propagation in two-phase heterogeneous porous media

The propagation of an acoustic wave through two-phase porous media with spatial variation in porosity is studied. The evolutionary wave equation is derived, and the propagation of an acoustic wave is numerically analyzed in application to marine sediments with various physical parameters.

cond-mat.soft↗
arXiv2015

Nonlinear three-wave interaction in marine sediments

Nonlinear interaction of three acoustic waves in a sandy sediment is studied in the frequency range where there is a considerable wave velocity dispersion. The possibility of an experimental observation of the generation of a sound wave by two pump waves propagating at an angle to each other is estimated.

cond-mat.soft↗
arXiv2015

Acoustic wave front reversal in a three-phase media

Acoustic wave front conjugation is studied in a sandy marine sediment that contains air bubbles in its fluid fraction. The considered phase conjugation is a four-wave nonlinear parametric sound interaction process caused by nonlinear bubble oscillations which are known to be dominant in acoustic nonlinear interactions in three-phase marine sediments. Two various mechanisms of phase conjugation are studied. One of them is based on the stimulated Raman-type sound scattering on resonance bubble oscillations. The second one is associated with sound interactions with bubble oscillations which frequencies are far from resonance bubble frequencies. Nonlinear equations to solve the wave-front conjugation problem are derived, expressions for acoustic wave amplitudes with a reversed wave front are obtained and compared for various frequencies of the excited bubble oscillations.

cond-mat.soft↗
arXiv2015

Nonlinear acoustic wave generation in a three-phase seabed

Generation of an acoustic wave by two pump sound waves is studied in a three-phase marine sediment that consists of a solid frame and the pore water with air bubbles in it. To avoid shock-wave formation the interaction is considered in the frequency range where there is a significant amount of sound velocity dispersion. Nonlinear equations are obtained to describe the interaction of acoustic waves in the presence of air bubbles. An expression for the amplitude of the generated wave is obtained and numerical analysis of its dependence on distance and on the resonance frequency of bubbles is performed.

cond-mat.soft↗
arXiv2009

On Entropy Wind in Superfluid Helium

Generation of a quasi-stationary flow of the superfluid helium normal part in the presence of intense first- and second-sound waves is studied. Relevant equations are obtained. The contribution to the process of energy dissipation at the shock front layer and of fluid viscosity is analysed in detail for the case of a second-sound wave. An estimate concerning possible experimental observation of the process is made.

cond-mat.other↗
arXiv2007

Nonlinear excitation of second sound in quantum solutions He3-He4 due to light wave absorption

Nonlinear excitation of second sound in superfluid solutions He3-He4 by light waves due to their absorption is discussed. Nonlinear wave equations that model the interaction of second-sound waves with light waves are derived, the expression for the nonlinear interaction length is obtained and an order-of-magnitude numerical estimate of the distance at which a second-sound wave could be amplified from a fluctuation level up to observable values is performed.

cond-mat.soft↗