arXiv subjects

Mikhail N. Shneider

Publications and source records attributed to Mikhail N. Shneider.

24 records · Page 2Linked to original sources

arXiv2019

Surface tension of small bubbles and droplets and the cavitation threshold

In this paper, using an unified approach, estimates are given of the magnitude of the surface tension of water for planar and curved interfaces in the pairwase interaction approximation based on the Lennard-Jones potential. It is shown that the surface tensions of a bubble and droplet have qualitatively different dependences on the curvature of the surface: for the bubble, as the radius of the surface's curvature decreases, the surface tension decreases, whereas it increases on the droplet. The corresponding values of the Tolman corrections are also determined. In addition, it is shown that the dependence of the surface tension on the surface's curvature is important for evaluating the critical negative pressure for the onset of cavitation.

physics.flu-dyn↗

arXiv2018

Particle-in-Cell Modeling of Laser Thomson Scattering in Low-Density Plasmas at Elevated Laser Intensities

Incoherent Thomson scattering is a non-intrusive technique commonly used for measuring local plasma density. Within low-density, low-temperature plasma's and for sufficient laser intensity, the laser may perturb the local electron density via the ponderomotive force, causing the diagnostic to become intrusive and leading to erroneous results. A theoretical model for this effect is validated numerically via kinetic simulations of a quasi-neutral plasma using the Particle-in-Cell technique.

physics.plasm-ph↗

arXiv2017

Ponderomotive perturbations of low density low-temperature plasma under laser Thomson scattering diagnostics

The ponderomotive perturbation in the interaction region of laser radiation with a low density and low-temperature plasma is considered. Estimates of the perturbation magnitude are determined from the plasma parameters, geometry, intensity and wavelength of laser radiation. It is shown that ponderomotive perturbations can lead to large errors in the electron density when measured using Thomson scattering.

physics.plasm-ph↗

arXiv2017

In situ Characterization of Nanoparticles Using Rayleigh Scattering

We report a theoretical analysis showing that Rayleigh scattering could be used to monitor the growth of nanoparticles under arc discharge conditions. We compute the Rayleigh scattering cross sections of the nanoparticles by combining light scattering theory for gas-particle mixtures with calculations of the dynamic electronic polarizability of the nanoparticles. We find that the resolution of the Rayleigh scattering probe is adequate to detect nanoparticles as small as C60 at the expected concentrations of synthesis conditions in the arc periphery. Larger asymmetric nanoparticles would yield brighter signals, making possible to follow the evolution of the growing nanoparticle population from the evolution of the scattered intensity. Observable spectral features include characteristic resonant behaviour, shape-dependent depolarization ratio, and mass-dependent line shape. Direct observation of nanoparticles in the early stages of growth with unobtrusive laser probes should give insight on the particle formation mechanisms and may lead to better-controlled synthesis protocols.

physics.chem-ph↗

arXiv2014

Pre-breakdown cavitation development in the dielectric fluid in the inhomogeneous, pulsed electric fields

We consider the development of pre-breakdown cavitation nanopores appearing in the dielectric fluid under the influence of the electrostrictive stresses in the inhomogeneous pulsed electric field. It is shown that three characteristic regions can be distinguished near the needle electrode. In the first region, where the electric field gradient is greatest, the cavitation nanopores, occurring during the voltage nanosecond pulse, may grow to the size at which an electron accelerated by the field inside the pores can acquire enough energy for excitation and ionization of the liquid on the opposite pore wall, i.e., the breakdown conditions are satisfied. In the second region, the negative pressure caused by the electrostriction is large enough for the cavitation initiation (which can be registered by optical methods), but, during the voltage pulse, the pores do not reach the size at which the potential difference across their borders becomes sufficient for ionization or excitation of water molecules. And, in the third, the development of cavitation is impossible, due to an insufficient level of the negative pressure: in this area, the spontaneously occurring micropores do not grow and collapse under the influence of surface tension forces. This paper discusses the expansion dynamics of the cavitation pores and their most probable shape.

physics.flu-dyn↗

arXiv2013

To the electrostrictive mechanism of nanosecond-pulsed breakdown in liquid phase

In this study we have studied the initial stage of the nanosecond-pulsed discharge development in liquid phase. Modeling predicts that in the case of fast rising strong nonhomogeneous electric fields in the vicinity of high voltage pin electrode a region saturated with nanoscale non-uniformities may be developed. This phenomenon is attributed to the electrostriction mechanisms and may be used to explain development of breakdown in liquid phase. In this work, schlieren method was used in order to demonstrate formation of negative pressure region in liquids with different dielectric permittivity constants: water, ethanol and ethanol-water mixture. It is shown that this density perturbation, formed at the raising edge of the high voltage pulse, is followed by a generation of a shock wave propagating with the speed of sound away from the electrode, with negative pressure behind it.

physics.plasm-ph↗