Swirling-modulated cavity dynamics and mixing characteristics in an industrial high-temperature submerged top-blowing system

Top-submerged lance technology is widely used in polymetallic resource processing, hazardous waste treatment, and critical material recycling for its high efficiency and material adaptability. While prior studies link increased swirling intensity with improved cooling efficiency, its systematic impact on bath stirring remains unclear. This study establishes a validated volume of fluid (VOF) model to investigate the gas–liquid flow dynamics of a submerged swirling jet. Key findings reveal that swirl intensity critically regulates cavity dynamics: the swirl generator converts axial momentum into tangential motion, enabling radial expansion via centrifugal force and inducing molen bath rotation through circumferential shear. The impact cavity undergoes periodic expansion and contraction, governed by the competition between the increased gas pressure caused by heating and gravity. The periodic evolution of the cavity morphology drives cyclical variations in bath kinetic energy, gas–liquid contact area, and splashing behaviors with a frequency of 2.5Hz. Furthermore, increasing the final-stage blade angle to 67.4° significantly enhanced swirl intensity, which led to a larger cavity volume, higher liquid kinetic energy, and an expanded interfacial area, while reducing the dead zone ratio from 32.9% to 17.1% and lowering wall shear stress. These improvements stem from a weakened axial impingement and a reduced cavity pressure release rate. Finally, the current study confirms that intensifying swirl, essential for lance cooling, simultaneously enhances mixing efficiency and equipment longevity, thereby resolving the conflict between cooling performance and bath stirring.