Modeling of the Partial Discharge Process in a Liquid Dielectric: Effect of Applied Voltage, Gap Distance, and Electrode Type

The partial discharge (PD) process in liquid dielectrics is influenced by several factors. Although the PD current contains the information representing the discharge process during the PD event, it is difficult to determine the detailed dynamics of what is happening in the bulk of the liquid. In this paper, a microscopic model describing the dynamics of the charge carriers is implemented. The model consists of drift-diffusion equations of electrons, positive and negative ions coupled with Poisson’s equation. The stochastic feature of PD events is included in the equation. First the model is validated through comparison between the calculated PD current and experimental data. Then experiments are conducted to study the effects of the amplitude of the applied voltage, gap distance and electrode type on the PD process. The PD currents under each condition are recorded. Simulations based on the model have been conducted to analyze the dynamics of the PD events under each condition, and thus explain the mechanism of how these factors influence the PD events. The space charge generated in the PD process is revealed as the main reason affecting the microscopic process of the PD events

Influence of external flows on crystal growth: numerical investigation

We use a combined phase-field/lattice-Boltzmann scheme [D. Medvedev, K. Kassner, Phys. Rev. E {\bf 72}, 056703 (2005)] to simulate non-facetted crystal growth from an undercooled melt in external flows. Selected growth parameters are determined numerically. For growth patterns at moderate to high undercooling and relatively large anisotropy, the values of the tip radius and selection parameter plotted as a function of the Peclet number fall approximately on single curves. Hence, it may be argued that a parallel flow changes the selected tip radius and growth velocity solely by modifying (increasing) the Peclet number. This has interesting implications for the availability of current selection theories as predictors of growth characteristics under flow. At smaller anisotropy, a modification of the morphology diagram in the plane undercooling versus anisotropy is observed. The transition line from dendrites to doublons is shifted in favour of dendritic patterns, which become faster than doublons as the flow speed is increased, thus rendering the basin of attraction of dendritic structures larger. For small anisotropy and Prandtl number, we find oscillations of the tip velocity in the presence of flow. On increasing the fluid viscosity or decreasing the flow velocity, we observe a reduction in the amplitude of these oscillations.Comment: 10 pages, 7 figures, accepted for Physical Review E; size of some images had to be substantially reduced in comparison to original, resulting in low qualit

Interfacial Micro-currents in Continuum-Scale Multi-Component Lattice Boltzmann Equation Hydrodynamics.

We describe, analyse and reduce micro-current effects in one class of lattice Boltzmann equation simulation method describing im-miscible fluids within the continuum approximation, due to Lishchuk et al. (Phys. Rev. E 67 036701 (2003)). This model's micro-current flow �field and associated density adjustment, when considered in the linear, low-Reynolds number regime, may be decomposed into independent, superposable contributions arising from various error terms in its immersed boundary force. Error force contributions which are rotational (solenoidal) are mainly responsible for the micro-current (corresponding density adjustment). Rotationally anisotropic error terms arise from numerical derivatives and from the sampling of the interface-supporting force. They may be removed, either by eliminating the causal error force or by negating it. It is found to be straightforward to design more effective stencils with significantly improved performance. Practically, the micro-current activity arising in Lishchuk's method is reduced by approximately three quarters by using an appropriate stencil and approximately by an order of magnitude when the effects of sampling are removed

The First Institute for the Humanities of Yakutia

Institute for the Humanities Research and the Indigenous Peoples of the North (IHR&IPN) of the Siberian Branch of the RAS is among the oldest academic institutions in Siberia. During its 75-year history it has become a leading center of the country in the integrated study of history, language and literature of unique ethnic groups inhabiting the North-East of Russia.Институт гуманитарных исследований и проблем малочисленных народов Севера (ИГИиПМНС) Сибирского отделения РАН относится к старейшим академическим учреждениям Сибири. За более чем 75-летнюю историю он превратился в ведущий центр страны по комплексному изучению истории, языка и литературы уникальных этносов, населяющих Северо-Восток России

Страницы истории Красноярского научного центра Сибирского отделения Российской академии наук

The article is devoted to academician L.V. Kirenskyis (1909-1969) work on organization of the first academic institute in Krasnoyarsk - Institute of Physics, which laid the foundation of development of the system of scientific institutions eventually united in Krasnoyarsk scientific centre (KSC) of SB RAS. Today Krasnoyarsk scientists achievements have become known to the whole world, and Krasnoyarsk scientific centre is an integral part of scientific and educational potential not only of the region but also of Russia as a whole.Статья посвящена деятельности академика Л.В. Киренского (1909-1969) по организации первого академического института в Красноярске – Института физики, положившего начало развитию сети научных учреждений, со временем объединенных в Красноярский научный центр СО РАН. Ныне достижения красноярских ученых известны всему миру, а Красноярский научный центр является неотъемлемой частью научно-образовательного потенциала не только региона, но и всей России

Dynamics of droplets moving on a solid surface: Lattice Boltzmann simulations

The three-dimensional dynamics of droplets on inclined and vertical walls in a gravity field is simulated. The dependence of a contact angle on a velocity of contact line is obtained for slow regime and smooth surface. The simulations of a rupture of the liquid films on the nonwettable solid substrate due to the thermocapillary effect (Marangoni effect) are also carried out. The lattice Boltzmann method is successfully implemented for computer simulation of these three-dimensional problems