Abstract: For the 200 mm×800 mm twin-strand slab mold, physical simulation experiment with a 1∶1 water model and numerical simulations based on the VOF multiphase flow and DPM discrete phase models were employed to systematically investigate the effects of nozzle structure parameters (bottom shape, inclination angle, and immersion depth) and process parameters (gas flow rate) on the flow field characteristics and slag layer behavior within the mold.The research found that a concave bottom nozzle combined with an 18° inclination angle could significantly reduce liquid surface fluctuations and flow velocity, enhancing the stability of the flow field.An immersion depth of 150 mm could effectively mitigate the disturbance of the flow to the liquid surface, and an gas blowing rate of 4-6 L/min ensured uniform slag layer coverage, preventing the exposure of molten steel. The study revealed the dominant role of the nozzle bottom shape and inclination angle, and proposed an optimized parameter combination, providing theoretical basis and practical guidance for improving the stability and quality of the cast slab in the continuous casting process of special cross-section slabs.

Key words: numerical simulation, water modeling, high casting speed, VOF model