Magnetohydrodynamics (MHD) treats the phenomena that arise in fluid dynamicsfrom the interaction of an electrically conducting fluid with the electromagnetic field. Thedevelopment of computational hydrodynamics has significantly improved the accuracy ofcalculations on mathematical models, but it is still difficult to choose the optimal turbulence models,mesh quality, model parameters to solve a particular problem. The aim of the work is to verify thecalculation of the conducting fluid flow in circular pipes and to determine the optimal error of theturbulence model calculation and the parameters of its use. The study was conducted on the basis ofa comparison of experimental studies by the PIV-method of velocimetry with the results of numericalcalculations. The liquid is considered viscous, incompressible, and electrically conducting. Controlnonlinear momentum equations are solved numerically using the method of control volumes.Comparison of velocity profiles showed that almost all models show a fairly good match with theresults of the experiment. Analysis of the sum of squares residuals of calculation points fromexperimental shows that the BSL Reynolds Stress turbulence model is the best for the flow withoutthe influence of the magnetic field, and the k-ɛ model is the best in the presence of a magnetic field.The SST k-ω model has quite enough results regardless of the Hartmann number. The number ofmesh elements has little effect on the ac-curacy of the pressure drop calculation. For simplegeometries it is enough to use meshes with the number of elements that does not exceed the 500000elements. According to all criteria, it is rational to choose the k-ɛ turbulence model for furthercalculations. This model has some shortcomings in the calculation of wall layers, but allows to obtainhigh-quality and adequate results for the flow of conducting fluid with a limit on the mesh elementsnumber.

The article analyses the process of making the coal-water slurry fuel. The main factors influencing the slurry rheological characteristics and, therefore, energy costs during its transportation are determined. The main attention is paid to the original coal ash content efficiency influence on the energy characteristics of the coal-water slurry fuel. In the work, the transformations of classical rheological equations were carried out taking into account the experimental dependence of the coal-water fuel effective viscosity on the feedstock ash content. As a result of the conducted transformations the dependence to determine the specific pressure loss due to the feedstock ash content was obtained. This has enabled to supplement the eligibility determination techniques for the grade of the coal used as the feedstock for the preparation of the coal-water fuel with rational energy and rheological characteristics. To substantiate the theoretical calculations, the article presents the results of the experimental studies on the effect of coal ash content on the specific pressure losses.

The unique properties of liquids that can interact with electric and magnetic fields are used in mechanical engineering, technology and medicine. The possibility of the influence of the magnetic field on the solid particles of the liquid in the pipeline allows cleaning of the solid walls of the pipeline, which is the object of the study. Magnetic liquids are solutions of ferromagnets in a liquid, and their physical properties in a magnetic field cause structural transformations in such liquids. The treatment of electrically conductive liquids in a magnetic field and their use for cleaning water from oil or oil residues are considered. On the basis of numerical modeling, the movement of solid particles of magnetite, which is part of an electrically conductive liquid, was investigated by jointly solving the equations of Reynolds, Maxwell, non-discontinuity and the turbulence model. The physical phenomena of the movement of solid particles of magnetite-based conductive liquid in various elements of the pipeline were determined, which improved the parameters of cleaning liquids contaminated with oil and oil. The magnetic particles of the electrically conductive liquid quite nicely fill the boundaries of the intersection if there is a flow reversal, as it happens in radiators. An increase in the intensity of the magnetic field leads to a change in the velocity profile of the conductive liquid, which prevents magnetite particles from penetrating close to the wall. An increase in the power of the magnetic field makes it possible to detach the contamination from the walls of the pipeline together with the solid particle of magnetite. A 73 % increase in wear in certain sections of the pipeline is due to the effect of the centrifugal force acting on the particle during rotation. The sudden expansion of the flow makes it difficult for particles to reach the pipe surfaces, which worsens the cleaning conditions. The number of particles on the surface is 82 % less compared to the absence of sudden expansion

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