Simulation of the influence of surface chemical composition on internal gas flow at large Knudsen numbers

On the basis of the developed model, an attempt to describe a rarefied gas flow in the cylindrical channel, whose surface chemical composition conforms with the real experimental conditions, has been made. During the modeling two cases are considered: the atomically clean silver channel surface and the surface fully covered with the adsorbate, which is simulated by oxygen according to the data of the Auger-spectroscopic analysis. The gas-surface interaction process is based on the molecular dynamic principle. Thermal vibrations of the surface atoms are also considered. The obtained results of calculation are compared with experimental data. © Copyright 2013 Published by Elsevier Ltd. All rights reserved

NUMERICAL SMILATIONS OF GAS FLOWS CONSIDERING SURFACE ROUGH STRUCTTURE

In this paper we numerically simulated the motion of gas particles inside the cylindrical and rectangular channels considering the influence of micro-rough surface. Simulation was performed with two methods: the method of the test particle and the method o f direct statistical simulation

GAS FLOW PARAMETERS DISTRIBUTION IN IDEAL APERTURE. STATISTICAL MODELING METHOD

In this research we numerically simulated the gas flow throught the ideal apperture using direct simulation Monte-Carlo method. Gas flow features such as temperature and velocity profiles are investigated

GAS FLOW PARAMETERS DISTRIBUTION IN IDEAL APERTURE. RAY TRACING METHOD

Ray tracing method used to calculate parameters and velocities in the Knudsen flow through a perfect round hole. It is assumed that in the steady state volume of wall emit particles with the equilibrium Maxwellian distribution function with different numerical density and temperature

Molecular Momentum Transport at Fluid-Solid Interfaces in MEMS/NEMS: A Review

This review is focused on molecular momentum transport at fluid-solid interfaces mainly related to microfluidics and nanofluidics in micro-/nano-electro-mechanical systems (MEMS/NEMS). This broad subject covers molecular dynamics behaviors, boundary conditions, molecular momentum accommodations, theoretical and phenomenological models in terms of gas-solid and liquid-solid interfaces affected by various physical factors, such as fluid and solid species, surface roughness, surface patterns, wettability, temperature, pressure, fluid viscosity and polarity. This review offers an overview of the major achievements, including experiments, theories and molecular dynamics simulations, in the field with particular emphasis on the effects on microfluidics and nanofluidics in nanoscience and nanotechnology. In Section 1 we present a brief introduction on the backgrounds, history and concepts. Sections 2 and 3 are focused on molecular momentum transport at gas-solid and liquid-solid interfaces, respectively. Summary and conclusions are finally presented in Section 4

Analysis of the state system of export financial support in Russia

Export promotion is one of the main goals of a national government. Foreign countries' experience indicates that the most effective mechanism of governmental support for national exporters in the establishment of so-called export agencies (or export-credit agencies) which insure, guarantee and credit export transactions. Despite significant amounts of money reserved for export promotion in the Federal Budget russian system of export support is inefficient. In the work we analyze main reasons for this, which are system incoherence, bureaucratic barriers and the absence of powerful export agency which could render national exporters a wide range of services form insurance to loans.Содействие развитию экспорта - важнейшая задача правительства любой страны. Опыт зарубежных государств показывает, что наиболее действенным механизмом государственной поддержки национальных экспортеров является создание экспортных агентств, которые осуществляют страхование, гарантирование и кредитование экспортных сделок. Несмотря на значительные средства, направляемые государством на поддержку отечественных экспортеров, в России система продвижения экспорта малоэффективна. Основными причинами этого являются разорванность системы, бюрократические барьеры и, самое главное, отсутствие влиятельного экспортного агентства, которое оказывало бы экспортерам всестороннюю поддержку по принципу «единого окна»

Neutralizer with a gas ejector

A neutralizer model with a gas ejector is studied, whose main element (a sonic nozzle) is a gap between two conical surfaces. Static pressure distributions were measured along the axis of the neutralizer at different gas pressures in the receiver. Stagnation pressure, total flow, gas target thickness, flow separation factor, Knudsen number, and gas-dynamic performance of the neutralizer were calculated from the gas pressure values on the axis of the neutralizer at the point with the coordinate z/d = 3, and static pressure distributions in the characteristic cross sections of the neutralizer were obtained. © 2012 Pleiades Publishing, Ltd

Generation of gas flows in symmetric neutralizer

This paper presents the results of experimental studies of the lengthwise distribution of the total and static pressure and the total flow of carbon dioxide in symmetrical neutralizers. These distributions are found to depend on the flow regimes and geometrical characteristics of gas injection. It is established that the density of the gas target per unit gas flow rate increases with increasing portion of the gas injected at the center of the neutralizes. © 2012 Pleiades Publishing, Ltd