Transient turbulent flow simulation with water model validation and application to slide gate dithering

Slide gate dithering can reduce nozzle clogging and sticking during continuous casting, but also influences transient flow in the mold and meniscus level fluctuations. In this work, a semi-analytical model was first developed and validated to predict nozzle flow rate from slide-gate opening position. A transient CFD model of 3-D turbulent flow was then validated with surface velocity measurements in a water model. Finally, transient two phase flow simulations were performed to investigate nozzle and mold flow pattern variations during gate dithering, with Upper Tundish Nozzle (UTN) hot argon injection rate and bubble size calculated with a porous-flow nozzle-refractory model, and steel flow rate calculated using the gate-position-based model. The transient simulation shows liquid steel jet wobbling and periodic gas-rich pockets entering the mold region during dithering. The mold level oscillates periodically during dithering, with about the same frequency, and the amplitude of the mold level fluctuations increases in proportion to the gate dithering stroke. Validation is provided by the match between the predictions and plant measurements of unfiltered mold level history.