Spatiotemporal analysis of the runaway distribution function from synchrotron images in an ASDEX Upgrade disruption

Synchrotron radiation images from runaway electrons (REs) in an ASDEX Upgrade discharge disrupted by argon injection are analysed using the synchrotron diagnostic tool Soft and coupled fluid-kinetic simulations. We show that the evolution of the runaway distribution is well described by an initial hot-tail seed population, which is accelerated to energies between 25–50 MeV during the current quench, together with an avalanche runaway tail which has an exponentially decreasing energy spectrum. We find that, although the avalanche component carries the vast majority of the current, it is the high-energy seed remnant that dominates synchrotron emission. With insights from the fluid-kinetic simulations, an analytic model for the evolution of the runaway seed component is developed and used to reconstruct the radial density profile of the RE beam. The analysis shows that the observed change of the synchrotron pattern from circular to crescent shape is caused by a rapid redistribution of the radial profile of the runaway density.

Optimization of argon injection into shroud of tundish during continuous casting: a numerical study

In order to prevent molten steel reoxidation in the tundish during continuous casting, argon injection into the shroud is applied. The injected argon bubbles in molten steel may change the molten steel flow pattern in the tundish. Consequently, the ratios of dead zone, plunger zone and well-mixed zone would change. Also, the motion of inclusions in the molten steel of tundish would change resulting from argon injection. The current word developed a coupling multiphase flow mathematical model. Basing on the developed model, the present work has researched the influences of argon injection on the molten steel flow pattern, inclusion motion characteristics in the tundish.

Physical and mathematical modeling of bubbles plume behaviour in one strand tundish

Moving through the liquid steel, argon bubbles intensify the chemical and thermal homogenisation processes and liquid metal refining. The present study reports the physical and mathematical modeling of bubbles behaviour in the tundish with argon injection system. The 210 litre–capacity one strand slab tundish model was made on a scale of 2:5. The laboratory water model experiments have demonstrated that the identical porous material used in gas-permeable barrier may generate gas bubbles varying in size and shape. This fact will also affect both vertical and horizontal velocities attained by the bubbles. From numerical simulations influence of argon flow rate on liquid steel velocity for free surface in the tundish was obtained. The results from numerical simulations indicate that argon create increasing of liquid steel velocity and vortex structures.