The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform

Yu V Fedorov - One of the best experts on this subject based on the ideXlab platform.

  • Sound Waves in a liquid with polydisperse vapor gas bubbles
    Acoustical Physics, 2016
    Co-Authors: D A Gubaidullin, Yu V Fedorov
    Abstract:

    A mathematical model is presented for the propagation of plane, spherical, and cylindrical Sound Waves in a liquid containing polydisperse vapor–gas bubbles with allowance for phase transitions. A system of integro-differential equations is constructed to describe perturbed motion of a two-phase mixture, and a dispersion relation is derived. An expression for equilibrium Sound velocity is obtained for a gas–liquid or vapor–liquid mixture. The theoretical results agree well with the known experimental data. The dispersion curves obtained for the phase velocity and the attenuation coefficient in a mixture of water with vapor–gas bubbles are compared for various values of vapor concentration in the bubbles and various bubble distributions in size. The evolution of pressure pulses of plane and cylindrical Waves is demonstrated for different values of the initial vapor concentration in bubbles. The calculated frequency dependence of the phase Sound velocity in a mixture of water with vapor bubbles is compared with experimental data.

  • Sound Waves in liquids with polydisperse vapor gas and gas bubbles
    Fluid Dynamics, 2015
    Co-Authors: D A Gubaidullin, Yu V Fedorov
    Abstract:

    A mathematical model determining the propagation of Sound Waves in the two-fraction mixture of a liquid with polydisperse vapor-gas and gas bubbles with account of phase transformations is presented. The system of integro-differential equations governing the disturbed flow of the two-phase mixture is written, the dispersion equation is derived, and the equilibrium speed of Sound is determined. The equilibrium speed of Sound is shown to decrease with increase in the vapor concentration. The theoretical predictions are compared with the available experimental data on the phase velocity in the water with vapor bubbles and in the mixture of freon with vapor bubbles.

  • Sound Waves in two fraction polydispersed bubbly media
    Journal of Applied Mathematics and Mechanics, 2013
    Co-Authors: D A Gubaidullin, Yu V Fedorov
    Abstract:

    Abstract The propagation of Sound Waves in two-fraction mixtures of a liquid with polydisperse gas bubbles of different composition is investigated. A system of differential equations of the perturbed motion of the mixture is presented, and a dispersion relation is derived. The equilibrium velocity of Sound, and the low-frequency and high-frequency asymptotic forms of the linear attenuation factor are obtained. The characteristic mean radii of the bubbles are determined. The theory is compared with existing experimental data.

H L Pecseli - One of the best experts on this subject based on the ideXlab platform.

  • weakly nonlinear ion Sound Waves in gravitational systems
    Physical Review E, 2020
    Co-Authors: P Guio, H L Pecseli
    Abstract:

    : Ion Sound Waves are studied in a plasma subject to gravitational field giving rise to vertically inhomogeneous steady-state plasma conditions. Such systems are interesting by exhibiting a wave growth that is a result of energy flux conservation for pulses propagating in an inhomogeneous system. The increase of the amplitude of a pulse as it propagates along the density gradient in the direction of decreasing density gives rise to an enhanced interaction between Waves and plasma particles that can be modeled by a modified Korteweg-de Vries equation. Analytical results are compared with numerical particle-in-cell simulations of the problem. Our code assumes isothermally Boltzmann distributed electrons resulting in a nonlinear Poisson equation. The ion component is treated as a collection of individual particles interacting through collective electric fields. Deviations from quasineutrality are allowed for.

  • weakly nonlinear ion Sound Waves in gravitational systems
    arXiv: Plasma Physics, 2019
    Co-Authors: P Guio, H L Pecseli
    Abstract:

    Ion Sound Waves are studied in a plasma subject to gravitational field. Such systems are interesting by exhibiting a wave growth that is a result of energy flux conservation in inhomogeneous systems. The increasing wave amplitude gives rise to an enhanced interaction between Waves and plasma particles that can be modeled by a modified Korteweg-de Vries equation. Analytical results are compared with numerical Particle-in-Cell simulations of the problem. Our code assumes isothermally Boltzmann distributed electrons while the ion component is treated as a collection of individual particles interacting through collective electric fields. Deviations from quasi neutrality are allowed for.

R Sunyaev - One of the best experts on this subject based on the ideXlab platform.

  • energy density of standing Sound Waves at the radiation dominated phase of the universe expansion hydrodynamic derivation
    Astronomy Letters, 2015
    Co-Authors: N A Inogamov, R Sunyaev
    Abstract:

    In the early Universe up to hydrogen recombination in the Universe, the radiation pressure was much greater than the pressure of baryons and electrons. Moreover, the energy density of cosmic microwave background (CMB) photons was greater than or close to the energy density contained in the rest mass of baryonic matter, i.e., the primordial plasma was a radiated-dominated one and the adiabatic index was close to 4/3. The small density perturbations from which the observed galaxies have grown grew as long as the characteristic perturbation scales exceeded the horizon of the Universe сt at that time. On smaller scales, the density perturbations were standing Sound Waves. Radiative viscosity and heat conduction must have led to the damping of Sound Waves on very small scales. After the discovery of the cosmic microwave background, J. Silk calculated the scales of this damping, which is now called Silk damping, knowing the CMBtemperature and assuming the density of baryons and electrons. Observations with the South Pole Telescope, the Atacama Cosmology Telescope, and the Planck satellite have revealed the predicted damping of acoustic peaks in the CMB power spectrum and confirmed one important prediction of the theory. In 1970, R.A. Sunyaev and Ya.B. Zeldovich showed that such energy release in the early Universe should lead to characteristic deviations of the CMB spectrum from the Planck one. The development of the technology of cryogenic detectors of submillimeter and millimeter wavelength radiation has made it possible to measure the CMB spectral distortions at 10−8 of its total intensity (PIXIE). This has sharply increased the interest of theoretical cosmologists in the problem of energy release when smallscale Sound Waves are damped. We have derived a relativistic formula for the energy of a standing Sound wave in a photon–baryon–electron plasma from simple hydrodynamic and thermodynamic relations. This formula is applicable for an arbitrary relation between the energy density of photons and the rest energy density of baryons and their thermal energy density. It continuously describes the transition between the two extreme cases. We obtain the expression for a radiation-dominated plasma in one limit and return to the expression for a gas of classicalmassive particles in the other limit. We have derived the relations that relate the amplitudes of velocity, baryon number density, and temperature perturbations in a radiation-dominated plasma of photons, baryons, and electrons.

  • mixing of blackbodies entropy production and dissipation of Sound Waves in the early universe
    Astronomy and Astrophysics, 2012
    Co-Authors: Rishi Khatri, R Sunyaev, Jens Chluba
    Abstract:

    Mixing of blackbodies with different temperatures creates a spectral distortion which, at lowest order, is a y-type distortion, indistinguishable from the thermal y-type distortion produced by the scattering of cosmic microwave background (CMB) photons by hot electrons residing in clusters of galaxies. This process occurs in the radiation-pressure dominated early Universe, when the primordial perturbations excite standing Sound Waves on entering the Sound horizon. Photons from different phases of the Sound Waves, having different temperatures, diffuse through the electron-baryon plasma and mix together. This diffusion, with the length defined by Thomson scattering, dissipates Sound Waves and creates spectral distortions in the CMB. Of the total dissipated energy, 2/ 3r aises the average temperature of the blackbody part of spectrum, while 1/3 creates a distortion of y-type. It is well known that at redshifts 10 5 < z < 2 × 10 6 , comptonization rapidly transforms y-distortions into a Bose-Einstein spectrum. The chemical potential of the Bose-Einstein spectrum is again 1/3 the value we would get if all the dissipated energy was injected into a blackbody spectrum but no extra photons were added. We study the mixing of blackbody spectra, emphasizing the thermodynamic point of view, and identifying spectral distortions with entropy creation. This allows us to obtain the main results connected with the dissipation of Sound Waves in the early Universe in a very simple way. We also show that mixing of blackbodies in general, and dissipation of Sound Waves in particular, leads to creation of entropy.

Frank P. Pijpers - One of the best experts on this subject based on the ideXlab platform.

D A Gubaidullin - One of the best experts on this subject based on the ideXlab platform.

  • Sound Waves in a liquid with polydisperse vapor gas bubbles
    Acoustical Physics, 2016
    Co-Authors: D A Gubaidullin, Yu V Fedorov
    Abstract:

    A mathematical model is presented for the propagation of plane, spherical, and cylindrical Sound Waves in a liquid containing polydisperse vapor–gas bubbles with allowance for phase transitions. A system of integro-differential equations is constructed to describe perturbed motion of a two-phase mixture, and a dispersion relation is derived. An expression for equilibrium Sound velocity is obtained for a gas–liquid or vapor–liquid mixture. The theoretical results agree well with the known experimental data. The dispersion curves obtained for the phase velocity and the attenuation coefficient in a mixture of water with vapor–gas bubbles are compared for various values of vapor concentration in the bubbles and various bubble distributions in size. The evolution of pressure pulses of plane and cylindrical Waves is demonstrated for different values of the initial vapor concentration in bubbles. The calculated frequency dependence of the phase Sound velocity in a mixture of water with vapor bubbles is compared with experimental data.

  • Sound Waves in liquids with polydisperse vapor gas and gas bubbles
    Fluid Dynamics, 2015
    Co-Authors: D A Gubaidullin, Yu V Fedorov
    Abstract:

    A mathematical model determining the propagation of Sound Waves in the two-fraction mixture of a liquid with polydisperse vapor-gas and gas bubbles with account of phase transformations is presented. The system of integro-differential equations governing the disturbed flow of the two-phase mixture is written, the dispersion equation is derived, and the equilibrium speed of Sound is determined. The equilibrium speed of Sound is shown to decrease with increase in the vapor concentration. The theoretical predictions are compared with the available experimental data on the phase velocity in the water with vapor bubbles and in the mixture of freon with vapor bubbles.

  • Sound Waves in two fraction polydispersed bubbly media
    Journal of Applied Mathematics and Mechanics, 2013
    Co-Authors: D A Gubaidullin, Yu V Fedorov
    Abstract:

    Abstract The propagation of Sound Waves in two-fraction mixtures of a liquid with polydisperse gas bubbles of different composition is investigated. A system of differential equations of the perturbed motion of the mixture is presented, and a dispersion relation is derived. The equilibrium velocity of Sound, and the low-frequency and high-frequency asymptotic forms of the linear attenuation factor are obtained. The characteristic mean radii of the bubbles are determined. The theory is compared with existing experimental data.