Sensitivity study of forced convection bubbling in a transparent viscous fluid as a proxy for molten borosilicate glass

Computational fluid dynamic and heat transfer models are being developed for the waste glass melters that will be used to vitrify legacy tank waste at the Hanford site. The objective of this study is to validate the ability of these models to predict the forced convection bubbling in the molten glass at prototypic conditions and scale. Bubbling is used to homogenize the melt pool and increase the melt rate of the batch. Simulations were compared with experimental data obtained with a surrogate liquid under isothermal conditions in an acrylic tank. The simulation results quantify the projected bubble area at the free surface as a function of flow rate and nozzle depth and show agreement with experimental data. Additionally, the local sensitivities of the surface tension and viscosity are evaluated for their effects, since in the melter this parameter directly affects the heat transfer from the molten glass to the reactive batch (or cold cap) layer. From the sensitivity study performed, the viscosity exhibits twice as much influence on bubble projected surface area as the surface tension. In comparison to the grid resolution used in this study, these glass properties produce higher levels of uncertainty.