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On the Calculation of the Vortex Sheet and Point Vortices Effects at Approximate Solution of the Boundary Integral Equation in 2D Vortex Methods of computational hydrodynamics

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FLUID DYNAMICS 2019年第7期54卷 991-1001页

作者： Kuzmina, K. S. Marchevskii, I. K. Bauman Moscow State Syst Univ Moscow Russia RAS Ivannikov Inst Syst Programming Moscow Russia

When simulating incompressible flow around airfoil using vortex methods of computational hydrodynamics, it is necessary to solve the boundary integral equation with respect to the intensity of the vortex sheet at the airfoil surface line. For its approximate solution, the Galerkin method with a piecewise-constant and piecewise-linear representation of the solution on the airfoil surface line can be applied. The coefficients of the system of linear equations, arising from the procedure of discretization of the integral equation, e xpress the influence of the vortex sheet located on the panels of the airfoil surface line on other panels;the components of the right-hand side vector express the influence of point vortices that simulate a vortex wake in the flow domain. For the case of the airfoil surface line approximation with a polyline consisting of rectilinear panels, exact analytical expressions are obtained for the coefficients of the matrix and the right-hand side vector;for the case of taking into account the curvature of the panels, an approach for their approximate calculation is proposed and all the necessary formulae are derived.

关键词： vortex methods boundary integral equation computational hydrodynamics

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Development of a Digital Twin of the Extruder for Production of Filament from Low Density Polyethylene

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CHEMISTRY AND TECHNOLOGY OF FUELS AND OILS 2024年第1期60卷 37-42页

作者： Gumerov, I. I. Ivlev, A. K. Kichatov, K. G. Prosochkina, T. R. Ufa State Petr Technol Univ Ufa Russia

On the basis of the characteristics of low-density polyethylene determined experimentally from the geometric dimensions of the extruder parts and COMSOL MULTIPHYSICS software a digital model of the apparatus was created, and the flow rate of the polymer melt from the extruder nozzle was calculated hydrodynamically. The agreement between the experimentally measured polymer flow rate and the value obtained from the model lies within the permissible error. This establishes the adequacy of the digital twin model, which will be used to predict the viscosity characteristics of composite materials based on low-density polyethylene and the technological regimes of their production by blending in the extruder.

关键词： extruder digital model COMSOL Multiphysics filament melt flow index finite element method computational hydrodynamics digital twin

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Numerical Modeling of the Heat Release in a DC Electroslag Remelting Furnace

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RUSSIAN METALLURGY 2023年第12期2023卷 1818-1823页

作者： Alekseev, I. A. Chumanov, I. V. Sergeev, D. V. South Ural State Univ Natl Res Univ Chelyabinsk 454080 Russia South Ural State Univ Natl Res Univ Zlatoust Branch Chelyabinsk 456209 Chelyabinskaya Russia

A steady-state numerical model has been developed for the working zone of an A-550 electroslag remelting pilot furnace operating at dc with changing polarity. The model consists of a software physical solver and a computational grid. A mathematical apparatus consisting of electric and thermodynamic components has been designed. The list of the properties of the involved substances and materials is presented. The numerical fields of the current density, heat, and temperature distributions over the slag pool thickness are calculated.

关键词： electroslag remelting electrothermy stationary nonconsumable electrode finite volume method computational hydrodynamics computer simulation numerical modeling

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Influence of the Swirling of an Equilibrially Dissociating Gas Flow in a Tube on Heat Exchange and Chemical Reaction in it

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JOURNAL OF ENGINEERING PHYSICS AND THERMOPHYSICS 2023年第3期96卷 763-775页

作者： Matviyenko, O. V. Martynov, P. S. Natl Res Tomsk State Univ 36 Lenin Ave Tomsk 634050 Russia Tomsk State Univ Architecture & Bldg 2 Solyanaya Sq Tomsk 634003 Russia

Results of mathematical simulation of the influence of the swirling of a flow of an equilibrially dissociating heattransfer agent (nitrogen tetroxide) in a tube on the heat transfer and the chemical reaction in it are presented. It is shown that an increase in the intensity of swirling of such a flow in a tube increases the rate of heat exchange in it, with the result that the Nusselt number of the flow increases. In this case, the heat transfer in the flow depends not only on the integral intensity of its swirling but also on the method of organization of the flow swirling. It was established that, in the case of active action of the centrifugal forces on this flow, the turbulent disturbances arising in it cause its heat-transfer coefficient to increase, and, in the case of conservative action of the centrifugal forces on the flow, its heat transfer coefficient decreases. It is shown that the rate of heat exchange in the indicated flow can be controlled by changing the tangential component of the velocity of the flow along the radius of the tube.

关键词： heat exchange chemical reaction boundary layer swirling flow computational hydrodynamics

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Modeling of Thermogasdynamics and Thermal Processes of Volatile Halides of Elements of III, IV and VI Groups in Thermal Plasma of RF-IC Discharge at Atmospheric Pressure

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PLASMA CHEMISTRY AND PLASMA PROCESSING 2022年第6期42卷 1381-1403页

作者： Shabarova, L., V Kornev, R. A. Ermakov, A. A. Shkrunin, V. E. Shishkin, A., I Belov, A. A. Kalyasov, P. S. GG Devyatykh Inst Chem High Pur Subst RAS 49 Tropinin Str Nizhnii Novgorod 603951 Russia RE Alekseev Nizhny Novgorod State Tech Univ 24 Minin Str Nizhnii Novgorod 603950 Russia Natl Res Lobachevsky State Univ Nizhny Novgorod 23 Prospekt Gagarina Nizhnii Novgorod 603022 Russia

A mathematical model has been proposed and verified, based on the combination of thermodynamic calculations of equilibrium plasma and CFD-modeling of the plasma-chemical reactor for hydrogen recovery of volatile halides. An experimental study of the hydrogen reduction processes of BCl3 and SiCl4 was carried out under conditions of RF-IC (RF inductively coupled) discharge at atmospheric pressure. Based on the experimental results, the developed mathematical model was validated. A series of numerical experiments on parametric study of gas dynamics of high-frequency plasmatron with vortex stabilization of flow for various hydrogen concentrations in argon-hydrogen plasma-forming mixture was carried out. Thermodynamic calculations and CFD modeling were made for input into the reaction chamber of chemically active gas mixtures (BCl3 + H-2), (BF3 + H-2), (SiCl4 + H-2), (SiF4 + H-2), (MoF6 + H-2), (WF6 + H-2), (BCl3 + CH4 + H-2), (BF3 + CH4 + H-2), (SiF4 + CH4 + H-2), (MoF6 + CH4 + H-2) and (WF6 + CH4 + H-2). The values for the predictive efficiency and the degree of conversion of target products were obtained.

关键词： computational hydrodynamics Thermodynamics Hydrogen recovery Volatile halides Isotopes

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EFFECT OF THE SHAPE OF PULSES ON HEAT TRANSFER AT THE STAGNATION POINT OF A NONSTATIONARY AXISYMMETRIC IMPACT GAS-DROPLET JET

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JOURNAL OF ENGINEERING PHYSICS AND THERMOPHYSICS 2022年第4期95卷 985-990页

作者： Pakhomov, M. A. Terekhov, V., I Russian Acad Sci Siberian Branch SS Kutateladze Inst Thermal Phys 1 Acad Lavrentiev Ave Novosibirsk 630090 Russia

A numerical investigation was carried out to study the influence of the shape of pulses (rectangular, triangular, and sinusoidal) on heat transfer at the stagnation point of an impact pulsed gas-droplet jet. It is shown that in a nonstationary two-phase impact jet both an increase and suppression of heat transfer are possible in comparison with stationary flow for all pulse shapes studied. In the region of small distances between the pipe cut and the barrier (up to four pipe diameters) in the pulsed gas-droplet jet, the heat transfer at the stagnation point increases, while at large distances (more than five pipe diameters), the heat transfer rate decreases in the pulsed flow. This is typical of all the pulse shapes studied in this work An increase in the Reynolds number causes a decrease in heat transfer intensification, and the results of calculations for all types of signal shapes approach the stationary mode of a two-phase impact jet.

关键词： impact nonstationary jet droplets shape of pulses heat transfer computational hydrodynamics

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Numerical Simulation of the Distribution of Hardening Dispersed Particles during Centrifugal Casting on a Machine with a Vertical Axis of Rotation

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RUSSIAN METALLURGY 2022年第6期2022卷 593-597页

作者： Chumanov, I. V. Anikeev, A. N. Novoselov, A. V. Alekseev, I. A. Natl Res Univ Zlatoust Branch South Ural State Univ Zlatoust 456209 Chelyabinsk obl Russia Natl Res Univ South Ural State Univ Chelyabinsk 454080 Russia

The mathematical apparatus of a model developed to describe the distribution of dispersed particles during centrifugal casting is described. The distribution of dispersed tungsten carbide particles in grade 20 steel during centrifugal casting on a centrifugal casting machine with a vertical axis of rotation is investigated. As a result of numerical simulation, the presence of a gradient distribution of dispersed particles is found and the limiting concentration of particles (0.008-0.013 g/cm(3)) is determined. The distribution of dispersed particles over the solidifying workpiece volume to be simulated is obtained.

关键词： centrifugal casting dispersed particles tungsten carbide distribution melt numerical simulation computational hydrodynamics

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Gravitational Instability of Circumnuclear Gas-and-Dust Disks in Nearby Galaxies

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VESTNIK ST PETERSBURG UNIVERSITY-MATHEMATICS 2022年第3期55卷 361-368页

作者： Tkachenko, R., V Korchagin, V., I Jmailov, B. B. Southern Fed Univ Inst Phys Rostov Na Donu 344090 Russia Southern Fed Univ Inst High Technol & Piezotech Rostov Na Donu 344090 Russia

Using two-dimensional multi-component hydrodynamic modelling, we study the effect of dust on the development of instability in mini-disks of gas and dust observed in the central regions of galaxies, in particular in NGC 4736. The dust is coupled with the gas gravitationally and by means of a friction force depending on the velocity difference between the two components. The presence of dust leads to instability of the mini-disk located at the external potential of the galaxy. The model makes it possible to explain the development of instability and the appearance of spiral structures observed in the mini-disks of gas and dust. The spiral structure is multi-armed, which is caused by the dominance of high order Fourier harmonics in unstable modes. The instability of circumnuclear gas-and-dust disks is an important mechanism for explaining the activity of galactic nuclei associated with the accretion of matter onto the central black hole. We find that the admixture of dust to the gas component with a dust-to-gas ratio of 10-20% significantly destabilizes the gas-dust disk, resulting in a saturation stage as early as 50-100 Ma.

关键词： circumnuclear disks numerical simulations computational hydrodynamics galactic centers

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Investigation of Hydrodynamic Flows in Micromodels of Double Porosity Media

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FLUID DYNAMICS 2021年第4期56卷 451-459页

作者： Solnyshkina, O. A. Batyrshin, E. S. Pityuk, Yu A. Bashkir State Univ Ctr Micro & Nanoscale Dynam Dispersed Syst Ufa Russia OOO RN BashNIPIneft Ufa Russia

Absract- Approaches for the experimental and numerical study of the distinctive features of fluid flow through media with double porosity that are based on micromodels of porous media and microfluidic technologies are proposed. The optic microscopy and tracer flow visualization methods are used to study experimentally fluid flow through model media. The numerical approach is based on the three-dimensional boundary element method accelerated with the use of the fast multipole method on heterogeneous computational architectures. The effect of structure parameters of micromodels on the flow distribution between the domains with different porosities is studied. Variation in the longitudinal and transvers velocity components in small and large pore channels is considered as functions of their geometric parameters and volumetric flow rate.

关键词： microfluidics experimental hydrodynamics micromodel double porosity computational hydrodynamics boundary element method flow visualization

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MATHEMATICAL SIMULATION OF HEAT TRANSFER AND CHEMICAL REACTIONS IN AN EQUILIBRIUM DISSOCIATING GAS

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JOURNAL OF ENGINEERING PHYSICS AND THERMOPHYSICS 2021年第2期94卷 437-449页

作者： Matvienko, O. V. Martynov, P. S. Tomsk State Univ 36 Lenin Ave Tomsk 634050 Russia Tomsk State Univ Architecture & Civil Engn 2 Solyanaya Sq Tomsk 634003 Russia

Results of investigations of the heat exchange in the turbulent flow of nitrogen tetroxide in a cylindrical channel are presented. The equilibrium stage of the dissociation reaction N2O4 reversible arrow 2NO(2) was considered. It was established that an increase in the temperature of the wall of the channel leads to an intensification of the chemical reaction proceeding in the N2O4 flow and causes the absorption of the heat, transferred from the channel wall, in this flow to increase, with the result that the temperature of the near-wall layers and the thickness of the thermal boundary layer in the chemically reactive gas flow decrease to a level lower than those of a chemically inert heat-transfer agent. It is shown that the use of a dissociating heat-transfer agent in a short channel is advantageous in the case where the rate of its flow is small, and, to increase the efficiency of heat exchange in a high-velocity flow of such an agent, it is necessary to increase the length of a heat exchanger. Approximation formulas for determining the criteria of heat exchange in flows of chemically inert and reactive gases have been obtained.

关键词： heat exchange chemical reaction dissociation boundary layer computational hydrodynamics

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