Transient fluid flow phenomena in a gas stirred liquid bath with top oil layer - Approach by numerical simulation and water model experiments

The flow characteristics in a gas stirred ladle with oil layer were investigated with the help of water model experiments and numerical simulation. The oil layer has a great influence on the fluid flow and mixing behavior in the ladle. While the mixing time decreased with the increase of the gas flow rates, the oil layer over the top of the bath extended the mixing time in the whole range of gas flow rates, and at constant gas flow rate, the mixing time was extended with the increase of oil thickness. From the results of water model experiments and numerical simulations, transient formation of plume eye from the start of gas bubbling was matched well each other. Based on water model experiment the plume eye size was found to increase with the increase of gas flow rates and to decrease with the increase of the oil thickness. These were precisely confirmed with numerical simulated results. From the results of numerical simulation flow pattern without oil layer showed that bubbles rising eventually made a recirculation loop at the central area of the bath forming uniformly distributed velocity vectors in the bath. This flow pattern regarded as a good flow pattern for the better mixing behavior. However, flow pattern with oil layer showed distorted and localized recirculating loop near side wall below oil layer. This eventually gave extended mixing time in the bath with oil layer.