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Electrovortex flow of liquid metal in a vessel relates to melt stirring in electrometallurgical processes and aggregates, such as welding, electroslag remelting, electrical arc furnaces and others. Maximum values of electromagnetic force and flow velocity develop in the zone between or under the electrodes, where sophisticated 3D flows are formed. In the paper, examples of electrovortex flows near two fully submerged electrodes with bifilar DC supply are discussed. The measured electrical potential and 3D self-magnetic field compared with results of numerical calculation and with a quasi 2D model of EM fields are discussed. Numerically computed 3D electrovortex flow patterns are presented for two regimes, i.e. (i) laminar and (ii) turbulent obtained with the LES approach. There is good qualitative and quantitative agreement between experimental data, analytical and numerical computation results, as well as with some previously published results. [ABSTRACT FROM AUTHOR]

Abstract: The results of numerical and experimental study of the effect of the Earth's magnetic field on the electric-vortex flow of liquid metal in a hemispherical container are presented. It is found that the combination of toroidal flow and azimuthal force caused by the interaction of an electric current flowing through the liquid metal with a relatively weak external magnetic field leads to an intense twist of the fluid. This effect can be observed, for example, in electrometallurgical aggregates. [ABSTRACT FROM AUTHOR]

With the help of numerical and experimental methods it was shown that a stationary external magnetic field, which causes an azimuthal swirl of axisymmetric electric flow, leads to the generation of intensive hydrodynamic self-oscillating processes in a current- carrying liquid metal. Calculations are in good agreement with experimental data. [ABSTRACT FROM AUTHOR]

The investigation of heat transfer characteristics during liquid metal flow in a horizontal tube with one-sided heating of the lower half of the tube is carried out. Experimental investigations are conducted using the mercury MHD complex of the Moscow Power Engineering Institute and the Joint Institute for High Temperatures, Russian Academy of Science, in the context of a long-term collaboration program. The characteristics of the averaged and fluctuation temperatures are considered in different sections over the length of the heating zone in the area of a homogeneous transverse magnetic field. The laminar liquid metal flow revealed the occurrence and development of a low-frequency quasi-harmonic temperature fluctuation with great intensity. [ABSTRACT FROM AUTHOR]

The results of the pressure pulsations measurements connected with the process of the vapor films explosive destruction near heated bodies were analyzed. It was stated that under such conditions false pressure pulses are generated. It was experimentally shown and approved by numerical calculations that such interference may be caused by pressure pulsations due to thermal interaction of the piezotransducers used in the experiments with the high-temperature fragments of vapor. The mechanism of the false pressure pulses generation process caused by the thermal deformation of the membrane that affects the pressure sensor (piezoelectric crystal) was described. [ABSTRACT FROM AUTHOR]

The results of experimental and computational studies of the processes accompanying the melting of metal samples heated in air using induced currents are presented. The materials used for the experimental models—spheres and cylinders with a characteristic size of 10 mm—were pure iron, nonferrous metals, and various grades of steel. An unusual physical effect observed in experiments with iron and steels and associated with the intense release of sparks from the samples was studied: small brightly glowing metal droplets. A possible thermomechanical mechanism for the emission of droplets is proposed, based on the occurrence of excess melt pressure during metal melting inside the volume of the sample, limited by the resulting solid shell consisting of iron oxides. Numerical calculations were carried out, the results of which generally confirm the hypothesis presented. [ABSTRACT FROM AUTHOR]

The present paper details a comparison of experimental and computational results for the electrovortex flow of mercury in cylindrical and semi-cylindrical vessels, which is driven by the direct electrical current supplied over top and bottom non-submerged electrodes. The time-averaged velocity of liquid metal computed using the LES model of turbulence qualitatively and quantitatively agrees with the measured profiles of the axial velocity for a cylindrical experimental setup. For a semi-cylindrical setup which represents possible "cold" physical modelling of MHD devices, the observed flow patterns at the free surface and the computed flow patterns also agree qualitatively. [ABSTRACT FROM AUTHOR]

The article discusses the horizontal swirling of axisymmetric electrovortex flows (EVF). It states that the velocities fields in a liquid metal tank were measured to verify the assumption that the swirling is a result of the external magnetic fields caused by currents that flow along the downleads. It adds that a numerical investigation of EVF was conducted based on the three-dimensional Navier-Stokes equation solution.

The article discusses a study on the aspects of vapor explosion. This paper explored the problems of vapor explosion which has been a puzzling state especially in the chain process of intense activity in vaporization. Mechanisms in the fragmentation of large fractions in hot liquid are explained giving concrete conditions.

Discusses the thermomechanical action of the fine fragmentation of liquid droplets subjected to vapor explosion. Fine fragmentation of melt into small particles with the surface of melt-liquid interaction increasing by orders of magnitude; Transition of nucleate boiling which implies that a mass of cool liquid comes in direct contact with a hot surface; Basic equations of internal pressure.

Results of the numerical and experimental study of electrovortex flow patterns under an external magnetic field are presented. Experiments and calculations were performed in hemispherical geometry; the eutectic alloy (InGaSn) was used as a working liquid. Calculations were made with an external axial magnetic field up to 1 T and experiments with a magnetic field up to 0.02 T. It is found that the dependence of the flow intensity on the magnetic field magnitude is substantially non-monotonic. [ABSTRACT FROM AUTHOR]

The characteristics of stationary, concentrated vortices of a special type are studied in a cylindrical coordinate system. A new solution for the problem of a concentrated vortex with three components of the velocity vector was constructed. It differs significantly from the previously known solution with two components of the velocity vector. The pressure distribution in a stationary concentrated vortex with and without Coriolis effect is found. The conditions under which the vortex is cyclonic are established. An analysis was conducted on ways to create a system of small vortices on the path of a tornado; with passage through these vortices, a tornado can weaken and disintegrate into a series of low-intensity vortices that are damped due to the forces of air viscosity and the friction force on the surface. Since the place and time of birth of a tornado are hard to predict and are often far from the necessary energy sources, a method for the organization of a rapid, protective obstacle system in the right place at the right time in the form of a system of concentrated vortices is discussed. It is proposed to use microwave electromagnetic radiation beams generated from airplanes or satellites as the source creating concentrated vortices on the tornado path. [ABSTRACT FROM AUTHOR]

Experimental and numerical results which summarize the influence of the external axial magnetic field on the pattern of flow which occurs when an electric current passes through a conducting medium between two hemispheres are presented. Calculations were made using different magnetohydrodynamic computational approaches and results compared. Methods presented in this paper involve electrodynamic approximation, non-inductive approximation and full coupled MHD problem. The discussed methods can be applied to calculate flow patterns in direct-current-arc furnaces and to other electrometallurgical problems. [ABSTRACT FROM AUTHOR]

The present paper presents the experimental and numerical results of an electrically induced flow in a cylindrical container (188 mm diameter) filled with a In–Ga–Sn alloy. The electric current is applied from copper electrodes of various diameters (4–8 mm) and varied from 100 to 700 A. The deformation of the free surface just under the electrode is reported in term of depth. At some critical current an arc develops around the electrode tip. To explore numerically what happens in such flows, calculations of the Magnetohydrodynamic (MHD) flow are performed. The numerical model is based on a potential formulation for the electromagnetic field. The evolution of the free surface flow is tracked with a VOF model. The electromagnetic parameters are fully coupled with the evolution of the free surface and the contact surface at the electrode. At low current density the interface is shifted downward by the pinch action of the Lorentz force. In the same time the rotational part of the Lorentz force drives the liquid metal flow in radial direction towards the electrode. The flow is accelerated towards the electrode and sinks in the form of a strong jet. At the high current density, the velocities are strong enough to induce further displacement of the interface by a Bernoulli mechanism. The combined action of the pinch and the rotational components of the Lorentz force on the interface displacement, scales as I 2 . The numerical and experimental results are in good agreements. [ABSTRACT FROM AUTHOR]

Linear and non-linear stability analysis of the interface between a thin vapor film and a layer of liquid in the presence of a steady heat flux from a metal surface heated to a high temperature, to the vapor film and then from vapor to the subcooled liquid is investigated. The temperature dependence of saturation pressure is taken into account. Boundary conditions on the vapor-liquid interface that generalizes the known correlations on the free surface of liquid in the gravity field are derived. The thermal processes on the phase boundary lead to the generation of weakly decaying periodic surface waves of low amplitude and may cause small length waves (ripple), which are not capillary ones. Thermal processes on the phase interface are capable to provide the stability of a film of lights vapor under a layer of heavy liquid in the gravity field. The explosive instability may arise in the non-linear stage due to a weak variation of the film thickness or superheating of liquids. [ABSTRACT FROM AUTHOR]

A procedure of estimating the area of contact between cold water and a hot hemispherical surface is developed and described. Synchronous measurements of pressure pulses in liquid, the temperature of a body, and characteristics of contact between a heated body and a coolant are performed under conditions of abrupt change of boiling modes (from film to nucleate boiling). Characteristic features of the investigated processes are determined, which are largely defined by the temperature of the hemisphere, by its thermophysical properties, and by the presence of surface oxide films. It is found that the maximal value of the amplitude of pressure pulses, which may be as high as ∼1 MPa in the experiments, is observed in the region of temperatures of the hot body which are close to the temperature of limiting superheat of water. The dependences are obtained of the rate of spreading of liquid and of the time of delay of its explosive boiling from the instant of boiling on the temperature of the hemisphere. [ABSTRACT FROM AUTHOR]

Controlling of electrovortex flows of liquid metal in a confined vessel is an essential feature of electrometallurgical technologies and aggregates, such as stirring, welding, electroslag remelting, electrical arc furnaces, etc. In the present study, the numerical model developed by the authors in previous studies has been improved to compute turbulent velocity and temperature fields for electrovortex flows of liquid metal in an experimental setup with the bifilar direct current supply over two fully submerged electrodes. Melt velocity and temperature fields were measured by applying a thermal-correlation method. The measured and computed results were compared. A good qualitative and quantitative agreement between the experimentally obtained data and the numerical computation results for the velocity field in several setup zones was found. [ABSTRACT FROM AUTHOR]

Complex experimental study and numerical simulation of liquid metal flow and heat transfer in various configurations affected by longitudinal or transverse magnetic fields under conditions close to the tokamak reactor have been performed. A specific feature of the heat transfer under these conditions is the combined exposure of a strong magnetic field and thermogravitational forces, which manifests itself in previously unknown effects. Among these effects are the existence, in some modes, of MHD heat transfer areas of "degraded" heat transfer, the extremely uneven distribution of heat transfer coefficients along the perimeter of the tube and abnormally high temperature fluctuations near the wall. These phenomena including negative ones should be considered in the further designs. [ABSTRACT FROM AUTHOR]

Relations are derived which enable one to assess the size of fragments of a liquid-metal droplet after its fragmentation formed in the case of instantaneous contact between a hot metal surface and a coolant. The obtained experimental data demonstrate that the amplitude of pressure pulses generated during vapor film collapse (second boiling crisis) is several times lower than the values required for triggering a spontaneous vapor explosion. The assumption is validated according to which progress in studying the process of triggering a spontaneous vapor explosion is associated primarily with advances in understanding the mechanism of fragmentation of individual droplet. [ABSTRACT FROM AUTHOR]

Results are given of an experimental investigation of the behavior of a vapor film on a highly superheated hemispherical surface immersed in water subcooled to the saturation temperature. The conditions of existence of vapor films on a hot surface and the characteristics of their collapse from the heating surface and transition to nucleate boiling are revealed, as well as the effects which accompany the vanishing of vapor film. The possibilities of internal triggering of fine fragmentation of hot melt and vapor explosion are discussed. [ABSTRACT FROM AUTHOR]

Investigates the local processes proceeding in the case of changing the boiling regime on a heated cylindrical rod with a hemispherical end immersed in water at a depth equal to the radius of the hemisphere. Vibrations of the vapor-film surface; Explosive regime of the development of instability leading to a vapor-film collapse.