Martins Sarma

This paper demonstrates particle tracking velocimetry performed for a model system wherein particle-laden liquid metal flow around a cylindrical obstacle was studied. We present the image processing methodology developed for particle detection in images with disparate and often low signal- and contrast-to-noise ratios, and the application of our MH...

This paper demonstrates particle tracking velocimetry performed for a model system wherein particle-laden liquid metal flow about a cylindrical obstacle was studied. We present the image processing methodology developed for particle detection in images with disparate and often low signal- and contrast-to-noise ratios, and the application of our MHT...

In metallurgical processing, non-metallic inclusions contaminating metallic materials are one highly relevant challenge. Bubble injection into molten metals boosts the inclusion control and removal, thus enhancing metal homogenisation and purification. Although this principle of bubble flotation has been used for a long time, the effects of bubble–...

A recently developed method for the contactless magnetic generation of cavitation is demonstrated for high-melting-point metals. The approach is based on the floating-zone technique, which is truly contactless and crucible-free as it uses electromagnetic forces. Using this method, ultra-high-temperature ceramic particles, such as TiN, TiB2 and TiC,...

Ladle metallurgical treatment affects the chemical composition and impurities in molten steel. To remove non-metallic inclusions, gas injection into the ladle and intense stirring by means of bubble flows are essential in the refining process. This paper reports on a model experiment that provides an insight into the bubble - particle interaction i...

We investigate directional solidification of the melt with solid inclusions by means of a non-invasive imaging technique-neutron radiography. For the first time results have revealed particle trapping in the solidifying melt at macro scale. It is shown that particle solidification in volume can be achieved when liquid and solid phases form a mushy...

This article reports on the simultaneous measurement of foam structure and attached particles employing neutron imaging. An aqueous foam sample is placed in the NEUTRA beamline at the Paul Scherrer Institut, enabling a spatial resolution of less than 200 μm to be achieved at a frame rate of more than 1 Hz. A forced drainage setup allows the liquid...

A contactless excitation of cavitation is possible by superposition of induction heating with a static axial magnetic field. This creates an alternating electromagnetic body force in a liquid metal which in turn produces pressure oscillations. Using this method, the onset of cavitation has been clearly observed in various liquid metals (tin, zinc,...

Dispersion of particles to produce metal matrix nanocomposites (MMNC) can be achieved by means of ultrasonic vibration of the melt using ultrasound transducers. However, a direct transfer of this method to produce steel composites is not feasible because of the much higher working temperature. Therefore, an inductive technology for contactless trea...

This paper presents qualitative and quantitative characterization of two-phase liquid metal flows agitated by the stirrer on rotating permanent magnets. The stirrer was designed to fulfil various eddy flows, which may have different rate of solid particle entrapment from the liquid surface and their homogenization. The flow was characterized by vis...

In this work, the stirring of liquid gallium in a rectangular crucible induced by four counter-rotating permanent magnets is investigated numerically. The mean velocity and turbulence kinetic energy for different distances of the magnets from the vessel with liquid metal and the magnet rotation rate are investigated. The flow is modeled using two t...

Understanding and optimization of movement of inclusions in intense liquid metal flows is significantly important for different types of melting, stirring and casting equipment, including electroinductive technologies that are able to agitate flow in conductive liquid significantly beyond turbulence level. Such investigation match various industria...

In this work, liquid gallium flow induced by four counter rotating permanent magnets in a rectangular vessel is investigated numerically and compared to the results obtained with the novel neutron radiography method. It is observed experimentally that the expected symmetric four-vortex structure transits to three eddies. We captured this effect num...

This experiment allowed to performed first time dynamic investigation of solid inclusions in electromagnetically stirred liquid metal. The well-known Particle Image Velocimetry technique was adopted and successfully applied for analysis of the neutron experiment providing full dynamics of particles in a liquid metal flow.

Due to the non-transparency of metals it is nearly impossible to observe how inclusions behave within a liquid metal. At the same time numerical models, which generally are powerful tools for design of different types of metallurgical and other equipment associated with liquid metal, usually contain a high number of degrees of freedom due to the co...

This paper presents the analysis of the first dynamic neutron radiography experiment that visualized motion of solid particles in liquid metal, which was stirred by a system of four counter-rotating magnets. The paper also contains the quantitative results derived from neutron images: the distribution of particle concentration, number of admixed pa...

Due to the non-transparency of metals it is nearly impossible to observe how solid inclusions behave within a liquid metal. At the same time numerical models, which generally are powerful tools for design of different types of metallurgical equipment, usually contain a high number of degrees of freedom due to the complexity of turbulent flows of li...

The present paper contains a report on the first neutron radiography experiment that visualized the motion of solid particles in liquid gallium in a rectangular vessel, which was stirred by a system of four counter-rotating magnets. The experiment has demonstrated that the neutron radiography is a promising experimental method for the investigation...

A model experimental setup was built aiming to ensure achievable similitude to large scale metal melting furnaces, where electromagnetic stirring is required to reduce the melting time and to achieve thermal and compositional uniformity. The widely used three-phase AC current linear travelling magnetic field inductor is substituted by a new energy-...

Multiple configurations of synchronously rotating permanent magnet cylinders magnetized across the axes are proposed for liquid metal stirring for homogenization as well as for pumping. Universal analytical model is used for an initial parameter analysis. Then experimental setups were built to perform physical modelling of the industrial applicatio...

The first neutron radiography experiment, which visualized motion of solid particles in liquid metal in a rectangular vessel stirred by a system of four counter-rotating magnets, was carried out. The experiment demonstrated that the neutron radiography is a promising experimental method for investigation of dynamics of particles in liquid metal.

It is of considerable basic scientific interest and commercially relevant to the involved industries to better understand the movement of impurities in electromagnetically agitated liquid metals. Both, gaseous and solid inclusions are of concern as they are detrimental to the quality of the final product. While the admixture of gas in certain insta...

The present paper contains a description and first results of a recent neutron radiography experiment that visualized admixing of solid particles in liquid gallium in a rectangular vessel, which was stirred by a system of four counter-rotating magnets.

The short video presented the raw results of the first neutron radiography experiment on visualisation of motion of solid inclusions in the flow of liquid metal. The flow in the rectangular vessel was induced by four counter-rotating magnets. The experiment was carried out in Paul Scherrer Institute (Villigen, Switzerland) on July 24-27, 2014.