Enhancement of Gas–Liquid Mixing in Side-Blown Smelting via Sinusoidal Pulsed Swirling Injection

To overcome the limited mixing efficiency associated with conventional steady-state side blowing in molten pool smelting, this study proposes a gas injection strategy that combines a swirl lance configuration with sinusoidal pulsed blowing. Using a volume-of-fluid (VOF) multiphase flow framework coupled with the Realizable k–ε turbulence model, the performance of constant-velocity blowing is systematically compared with sinusoidal pulsed blowing over a range of amplitudes (5, 10, and 15 m/s) and frequencies (0.5, 1, and 2 Hz). The results demonstrate that sinusoidal pulsed blowing markedly enhances gas–liquid mixing within the melt pool relative to constant-speed injection. Mixing efficiency increases with blowing amplitude, while its dependence on pulse frequency is nonlinear. Within the investigated parameter space, the optimal configuration, an amplitude of 15 m/s and a frequency of 1 Hz, raises the average gas volume fraction by 8%, reduces the mixing dead-zone area by 81%, and expands the active mixing region by 25%. Overall, the imposed sinusoidal pulsing promotes bubble breakup beneath the free surface, leading to more complete bubble collapse, intensified turbulent agitation, and, ultimately, improved gas–liquid mixing.