RAS Dorodnicyn Computing Center

Moscow, Russia

RAS Dorodnicyn Computing Center

Moscow, Russia
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Rovenskaya O.I.,RAS Dorodnicyn Computing Center
International Journal of Heat and Mass Transfer | Year: 2017

The rarefied gas flow caused by a pressure drop in a planar microchannel of finite length is analysed numerically to investigate the effect of surface roughness on thermal and hydrodynamic flow characteristics. The kinetic approach based on the nonlinear S-model of the Boltzmann kinetic equation coupled with the Maxwell's diffuse gas-surface interaction model imposed at the wall is used. An implicit scheme for the solution of the S-model kinetic equation is applied and the algorithm has been optimised for the use of massive parallelization in the velocity space. A surface roughness is configured with series of triangular, semicircular, trapezoidal and rectangular obstructions. A competition between rarefaction and effects of roughness geometry is estimated by varying a rarefaction regime of flow from continuum up to free–molecular regime. The results indicate that the global flow performances in terms of the Poiseuille number, mass and thermal energy flow rates are affected by the wall roughness geometry when compared to the flow performances for a smooth channel. The triangular roughness produces the smallest impact on a gas flow, while the rectangular roughness the largest one. Rarefaction plays a significant role enhancing the effect of the surface roughness. In the continuum flow regime the roughness elements induce strong recirculation and flow separation regions. Moreover, the weakly rarefied flow strongly depends on the shape and the spacing of roughness elements. On the other hand, for the highly rarefied flow the global parameters are almost independent of the shape of elements. The increase in the spacing of roughness elements results in the reduction of the Poiseuille number and an enhancement of mass and thermal energy flow rates for all shapes of roughness elements. © 2017


Grant
Agency: European Commission | Branch: FP7 | Program: CSA | Phase: ICT-2013.10.3 | Award Amount: 1.03M | Year: 2014

In the fluid environment of the junction between FP7 and HORIZON 2020, the EAST HORIZON Support Action, brought forward by a balanced mixture of European Strategic Consulting companies, IT Industry, EECA National Research and Governmental Organizations, comes as a bridge for a two-way cooperation between the EECA and the EU.\nIt will inspire ideas, influence policies, and launch actions to:\nSupport the Dialogue between EU and EECA countries\nRaise awareness, help networking EECA organizations for participating in EU R&D and EU organizations participate in EECA R&D Programs.\nMatching EECA Societal Challenges, ICT R&D and Industrial Priorities to HORIZON 2020 concepts, EAST HORIZON, after validating results from previous related projects, will focus on new elements introduced by H2020 and the current frame of policy Dialogue between EU and EECA countries and bring concrete ideas and arguments to the Dialogue between the EC and EECA countries, in the perspective of a coherent ICT R&D cooperation policy.\nThe project will raise awareness by focused events where a deep insight of all relevant EU ICT R&D Frameworks will be provided; reciprocally it will gather feedback on EECA R&D Programs for enabling EU organizations participate in them.\nThe project will create a dense grid of relevant players on the two sides (ICT researchers, IT Associations, Companies, ETPs, Knowledge Networks and Policy makers) in a balanced way so as to maximize research collaboration, in parallel promoting innovation. This will shape new or strengthen existing business links between the EU and EECA IT Industries and Academia/Institutes.\nA permanent communication and collaboration platform, an environment where all ICT Research players meet and work together to raise ideas for joint Research projects will be established. The platform, linked to similar platforms, will be transferred to EECA stakeholders at project end, for achieving sustainability of collaboration mechanisms built under EAST HORIZON.


Titarev V.A.,RAS Dorodnicyn Computing Center
International Journal of Heat and Mass Transfer | Year: 2012

The paper presents a numerical analysis of the nonlinear rarefied gas flow through a long planar channel of finite length. The solution is constructed for the arbitrary pressure and temperature drops, including flow into vacuum. The obtained results for the flow rates are compared with the linearized solutions in the large range of degree of gas rarefaction. The boundaries of the validity of the linearized approximation are established. © 2012 Elsevier Ltd. All rights reserved.


Titarev V.A.,RAS Dorodnicyn Computing Center
Vacuum | Year: 2013

The paper is devoted to the study of a rarefied gas flow through a circular pipe caused by small pressure differences between the reservoirs attached to the ends of the pipe. The analysis is based on of the direct numerical solution of the Boltzmann kinetic equation with the linearized model collision integral of Shakhov. The solution of the problem is computed for a wide range of the rarefaction parameter values and is compared with the kinetic and continuum solutions for an infinitely long circular pipe as well as with the flow into vacuum. © 2013 Elsevier Ltd. All rights reserved.


Titarev V.A.,RAS Dorodnicyn Computing Center
Communications in Computational Physics | Year: 2012

The paper is devoted to the development of an efficient deterministic framework for modelling of three-dimensional rarefied gas flows on the basis of the numerical solution of the Boltzmann kinetic equation with the model collision integrals. The framework consists of a high-order accurate implicit advection scheme on arbitrary unstructured meshes, the conservative procedure for the calculation of the model collision integral and efficient implementation on parallel machines. The main application area of the suggested methods is micro-scale flows. Performance of the proposed approach is demonstrated on a rarefied gas flow through the finite-length circular pipe. The results show good accuracy of the proposed algorithm across all flow regimes and its high efficiency and excellent parallel scalability for up to 512 cores. © 2012 Global-Science Press.


Faustov R.N.,RAS Dorodnicyn Computing Center | Galkin V.O.,RAS Dorodnicyn Computing Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

The form factors of weak decays of Bs mesons to ground state Ds(*) mesons as well as to their radial Ds(*)(2S) and orbital DsJ(*) excitations are calculated in the framework of the relativistic quark model based on the quasipotential approach. All relativistic effects, including contributions of intermediate negative-energy states and boosts of the meson wave functions, are consistently taken into account. As a result, the form factors are determined in the whole kinematical range without additional phenomenological parametrizations and extrapolations. On this basis, semileptonic decay branching fractions are calculated. Two-body nonleptonic Bs decays are considered within the factorization approximation. The obtained results agree well with available experimental data. © 2013 American Physical Society.


Faustov R.N.,RAS Dorodnicyn Computing Center | Galkin V.O.,RAS Dorodnicyn Computing Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

The form factors of the weak Bs transitions to ground-state and orbitally excited strange mesons are calculated in the framework of the QCD-motivated relativistic quark model based on the quasipotential approach. These form factors are expressed through the overlap integrals of meson wave functions found in their mass spectrum evaluations. The momentum dependence of the form factors is determined in the whole accessible kinematical range without any additional assumptions and extrapolations. Relativistic effects, including the wave function transformation from rest to a moving reference frame as well as the contributions of the intermediate negative-energy states, are consistently taken into account. The calculated form factors are used for the evaluation of the charmless semileptonic decay rates and two-body nonleptonic Bs decays in the factorization approximation. The obtained results are confronted with previous predictions and available experimental data. © 2013 American Physical Society.


Azarova O.A.,RAS Dorodnicyn Computing Center
Aerospace Science and Technology | Year: 2015

The instabilities and vortices which arise as a result of an energy release effect on a shock layer produced by a blunt cylinder in a supersonic flow are considered. An energy deposition is supposed to have a shape of an infinite heated rarefied channel. The Richtmyer-Meshkov instability accompanied by the secondary instability is simulated inside a front separation area at Mach 1.9. The secondary Kelvin-Helmholtz instability is shown to be generated on the shear layers inside the density stratified vortex caused by the Richtmyer-Meshkov instability. Vortex drag reduction via the Richtmyer-Meshkov instability origination is discussed. The baroclinic nature of the vorticity production is established for the instabilities. Complex conservative difference schemes are used in the calculations. © 2015 Elsevier Masson SAS.


Shemyakova E.,RAS Dorodnicyn Computing Center
Programming and Computer Software | Year: 2012

The paper is devoted to the Darboux transformations, an effective algorithm for finding analytical solutions of partial differential equations. It is proved that Wronskian-like formulas suggested by G. Darboux for the second-order linear operators on the plane describe all possible differential transformations with M of the form D x + m(x, y) and D y + m(x, y), except for the Laplace transformations. © Pleiades Publishing, Ltd., 2012.


Titarev V.A.,RAS Dorodnicyn Computing Center
Journal of Computational Physics | Year: 2012

An efficient numerical algorithm for calculating rarefied gas flows in planar microchannels on the basis of the Boltzmann kinetic equation with the linearized S-model collision integral is presented. The algorithm consists of a high-order spatial discretisation on unstructured meshes, conservative procedure to calculate macroscopic quantities and efficient one-step implicit time evolution method. It therefore works across all flow regimes from the free-molecular to nearly continuum ones and provides rapid convergence to steady state solutions. The parallel implementation is provided via MPI programming paradigm. The performance of the method is illustrated by computing the flow for length to the width ratios for up to 10 3 in the wide range of Knudsen numbers. Numerical estimates of efficiency of implicit time marching and parallel performance as well as convergence studies in both physical and velocity spaces are provided. The end effects and other essentially two-dimensional features of the flow are analysed and a detailed comparison with the case of an infinitely long channel is carried out. The presented numerical data can be used as reference for future studies of nonlinear flows as well as for comparison with other numerical approaches and flow models. © 2011 Elsevier Inc.

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