• CONSERVING OF THE RESOURCES

    The increase in the yield of vegetables in greenhouses using supercavitation treatment of irrigation water

    Mechanization in agriculture & Conserving of the resources, Vol. 65 (2019), Issue 5, pg(s) 163-166

    The use of hydrodynamic and thermophysical effects of cavitation (cavitational technology) facilitates mechanical thermolysis of the water structure with free hydrogen bonds production, dispersion and solution annealing treatment to produce resistant emulsions, suspensions, and mixtures finally promising to improve and intensify the processes in various industries. There are given the results of the cavitation treatment effect on the properties of water which at times is a dispersed phase and at other times is a dispersion medium. In agriculture the use of the cavitation-treated water allows to get a crop capacity gain for greenhouse vegetable cultures up to 30 % with simultaneous reduction of plants morbidity. It is obvious that the major factors influencing the produced effect are the increased oxygen content of the treated (activated) water as well as the complex physical and chemical processes occurring under the cavitation effect: redox reactions that proceed in the water between the dissolved substances and the water splitting products emerging in cavitation bubbles and passing into the solution after their collapse; reactions between the dissolved gases inside cavitation bubbles; chain reactions in the solution initiated by the products of splitting in impurities cavitation bubbles; macromolecules break-down and its initiated polymerization; water structure change with the production of free hydrogen bonds, etc.

  • Acoustic cavitation in grain sprouting

    Mechanization in agriculture & Conserving of the resources, Vol. 65 (2019), Issue 1, pg(s) 27-29

    Feeding of rooster sires with sprouted grain significantly increases their productivity. A new acoustic cavitation method of intensification of grain sprouting process is offered. In water sound waves are created. When passing sound waves in water in a vakuummetric phase liquid is broken off with formation of cavitational cavities. These cavities collapse in a manometrical phase of a sound wave. Influence of the collapsing cavitational cavities causes a stress of biological object, its fast awakening and the accelerated development. At the same time there is a heating and decrease in viscosity of liquid substances, increase of speed of chemical, physical, biological processes. Massage action from a collapse on membranes of cages strengthens diffusion and a metabolism through membranes and in cages. Dynamic impulses kill pathogenic microorganisms, and without chemical reagents and at low temperatures (200 – 300), that is without destruction of protein and mechanical damages etc.
    Wheat seeds were treated in the passive zone of a vortex cavitator. This resulted in germinating ability increase on the third day from 43% to 88%, or in germination time reduction from three to one day along with the quality level comparable with the control lots. Germination ability of vortex cavitator-treated seeds at all modes, except for t=500, exceeds the germination ability of control lots sprouted with a traditional method.
    Excess germination ability of the treated seeds in rela tion to the control lots is 200%, thus assuming a twofold feed quality improvement.
    Germination ability of vortex cavitator-treated seeds after the first sprouting day is comparable with the control lot germination on the third day. This gives the possibility to reduce technological process time up to one day with the existing quality level. Irrigation of seeds treated in a vortex cavitator with water from the active cavitator zone increases germinating ability up to 97%, or reduces process time from three days to six hours providing the quality comparable with the original process.
    In this method of processing some ways of impact on biological object are combined: soaking, thermal influence, vibration, cavitational, diffusive, etc. All seeds processed on a cavitator have the raised development indicators in relation to seeds of control party including on viability, energy of germination, this grain positively influences efficiency of roosters.

  • Simulation of three-dimensional cavitation in radial divergent test section using different mass transfer models

    Mathematical Modeling, Vol. 3 (2019), Issue 1, pg(s) 21-24

    Cavitation is a phenomenon of liquid transition to vapour which occur at sudden drop in pressure. It can be studied experimentally using visualization techniques or numerically using numerical packages. In order to numerically predict cavitation Reynolds Averaged Navier Stokes equations and an additional transport equation for the liquid volume fraction can be used. In the additional transport equation mass transfer rate due to cavitation is modelled using different mass transfer models. In the presented paper cloud cavitation in radial divergent test section was studied numerically using three different widespread mass transfer models. The models used were Zwart, Kunz and Singhal mass transfer models. Zwart model is a native model of ANSYS CFX program while other two were implemented to the program. Steady state and transient RANS simulations were performed using the simulation program, standard k-e turbulence model and scalable wall functions. The results of numerical simulations were compared with the results of experimental measurements performed at the University of Grenoble. Based on the presented results we concluded that all mass transfer models correctly predict the area of cloud cavitation formation.

  • Finite area algorithm for thin film cavitation in openfoam

    Trans Motauto World, Vol. 4 (2019), Issue 1, pg(s) 3-7

    Numerical algorithm for calculating thin film cavitational effects is presented in this paper. Cavitation is a common phenomenon in diverging parts of thin film contacts, such as: journal bearings, ball bearings, seals, etc. Locating and calculating cavitational effects is very important for their applicability, efficiency and safety. The thin film flow solver based on the Reynolds equation, together with cavitation algorithm is implemented using the Finite Area Method inside the OpenFOAM framework. OpenFOAM is an open source C++ toolbox for computational fluid dynamics (CFD). The Finite Area Method is a two-dimensional counterpart of the Finite Volume Method, used for discretising partial differential equations over curved surfaces. Discretisation is performed on user selected patches of computational mesh, with values calculated at face centres and fluxes calculated at edge centres of each finite area face. Reynolds equation is a 2D partial differential pressure equation used for calculating thin film flows between two surfaces in relative motion, with the following assumptions: fluid viscous forces dominate over body, inertia and surface tensions forces; fluid film curvature can be neglected; variation of pressure across the fluid film is negligibly small. The implemented cavitation algorithm is capable of capturing both rupture and reformation boundaries during cavitation, therefore it is considered to be mass conserving. The implemented solver is validated on three test cases: single parabolic slider (1D), twin parabolic slider (1D) and microtexture pocket bearing (2D).